SpringBoot注解分析
SpringBoot注解分析
常用注解
@Component
放在类上，把普通类实例化到spring容器中。大多数注解都基于这个注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Indexed
public @interface Component {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
* @return the suggested component name, if any (or empty String otherwise)
* *该值可能表示逻辑组件名称的建议，
*在自动检测到组件的情况下转换为springbean。
*@返回建议的组件名称（如果有）（否则返回空字符串）
*/
String value() default "";
}
@Bean
放在方法上，用@Bean标注方法等价于XML中配置bean，这个方法一般返回一个实体对象，告诉spring这里产生一个对象，然后这个对象会交给Spring管理。产生这个对象的方法Spring只会调用一次，随后这个Spring将会将这个Bean对象放在自己的容器中。
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Bean {
/**
* Alias for {@link #name}.
* Intended to be used when no other attributes are needed, for example:
* {@code @Bean("customBeanName")}.
* @since 4.3.3
* @see #name
*{@link\name}的别名。
*
在不需要其他属性时使用，例如：
*{@code@Bean（“customBeanName”）}。
*@从4.3.3开始
*@见姓名
*/
@AliasFor("name")
String[] value() default {};
/**
* The name of this bean, or if several names, a primary bean name plus aliases.
* If left unspecified, the name of the bean is the name of the annotated method.
* If specified, the method name is ignored.
*
The bean name and aliases may also be configured via the {@link #value}
* attribute if no other attributes are declared.
* @see #value
*这个bean的名称，或者如果是多个名称，则是一个主bean名称加上别名。
*
如果未指定，bean的名称就是带注释的方法的名称。
*如果指定，则忽略方法名。
*
bean名称和别名也可以通过{@link#value}配置
*属性，如果没有声明其他属性。
*@见#值
*/
@AliasFor("value")
String[] name() default {};
/**
* Are dependencies to be injected via convention-based autowiring by name or type?
* Note that this autowire mode is just about externally driven autowiring based
* on bean property setter methods by convention, analogous to XML bean definitions.
*
The default mode does allow for annotation-driven autowiring. "no" refers to
* externally driven autowiring only, not affecting any autowiring demands that the
* bean class itself expresses through annotations.
* @see Autowire#BY_NAME
* @see Autowire#BY_TYPE
* @deprecated as of 5.1, since {@code @Bean} factory method argument resolution and
* {@code @Autowired} processing supersede name/type-based bean property injection
*依赖项是否通过基于约定的自动连线按名称或类型注入？
*
请注意，此自动布线模式只是基于外部驱动的自动布线
*在bean属性设置器方法上，类似于xmlbean定义。
*
默认模式允许注释驱动的自动连接。”否”指
*仅外部驱动自动布线，不影响任何自动布线要求
*bean类本身通过注释来表达。
*@按姓名查看自动连线
*@按类型查看Autowire
*由于{@code@Bean}工厂方法参数解析和
*{@code@Autowired}处理取代基于名称/类型的bean属性注入
*/
@Deprecated
Autowire autowire() default Autowire.NO;
/**
* Is this bean a candidate for getting autowired into some other bean?
* Default is {@code true}; set this to {@code false} for internal delegates
* that are not meant to get in the way of beans of the same type in other places.
* @since 5.
*这个bean是否可以自动连接到其他bean中？
*
默认值是{@code true}；对于内部委托，将此设置为{@code false}
*这并不意味着会妨碍其他地方相同类型的bean。
*@从5.1开始
*/
boolean autowireCandidate() default true;
/**
* The optional name of a method to call on the bean instance during initialization.
* Not commonly used, given that the method may be called programmatically directly
* within the body of a Bean-annotated method.
* The default value is {@code ""}, indicating no init method to be called.
* @see org.springframework.beans.factory.InitializingBean
* @see org.springframework.context.ConfigurableApplicationContext#refresh()
*在初始化期间调用bean实例的方法的可选名称。
*不常用，因为该方法可以通过编程方式直接调用
*在Bean注释的方法体中。
*
默认值是{@code“”}，表示不调用init方法。
*@看到了吗org.springframework.beans.factory.InitializingBean
*@看到了吗org.springframework.context.ConfigurableApplicationContext#刷新（）
*/
String initMethod() default "";
/**
* The optional name of a method to call on the bean instance upon closing the
* application context, for example a {@code close()} method on a JDBC
* {@code DataSource} implementation, or a Hibernate {@code SessionFactory} object.
* The method must have no arguments but may throw any exception.
* As a convenience to the user, the container will attempt to infer a destroy
* method against an object returned from the {@code @Bean} method. For example, given
* an {@code @Bean} method returning an Apache Commons DBCP {@code BasicDataSource},
* the container will notice the {@code close()} method available on that object and
* automatically register it as the {@code destroyMethod}. This 'destroy method
* inference' is currently limited to detecting only public, no-arg methods named
* 'close' or 'shutdown'. The method may be declared at any level of the inheritance
* hierarchy and will be detected regardless of the return type of the {@code @Bean}
* method (i.e., detection occurs reflectively against the bean instance itself at
* creation time).
*
To disable destroy method inference for a particular {@code @Bean}, specify an
* empty string as the value, e.g. {@code @Bean(destroyMethod="")}. Note that the
* {@link org.springframework.beans.factory.DisposableBean} callback interface will
* nevertheless get detected and the corresponding destroy method invoked: In other
* words, {@code destroyMethod=""} only affects custom close/shutdown methods and
* {@link java.io.Closeable}/{@link java.lang.AutoCloseable} declared close methods.
*
Note: Only invoked on beans whose lifecycle is under the full control of the
* factory, which is always the case for singletons but not guaranteed for any
* other scope.
* @see org.springframework.beans.factory.DisposableBean
* @see org.springframework.context.ConfigurableApplicationContext#close()
*关闭时调用bean实例的方法的可选名称
*应用程序上下文，例如JDBC上的{@code close（）}方法
*{@code DataSource}实现，或Hibernate{@code SessionFactory}对象。
*方法必须没有参数，但可能引发任何异常。
*
为了方便用户，容器将尝试推断销毁
*方法对从{@code@Bean}方法返回的对象。例如，给定
*返回apachecommons DBCP{@code BasicDataSource}的{@code@Bean}方法，
*容器将注意到该对象上可用的{@code close（）}方法，并且
*自动将其注册为{@code destroyMethod}。这种“毁灭”方法
*“推断”当前仅限于检测名为的公共方法，而不是参数方法
*“关闭”或“关闭”。方法可以在继承的任何级别上声明
*无论{@code@Bean}的返回类型如何，都将检测到
*方法（即，对位于
*创建时间）。
*
要禁用特定{@code@Bean}的销毁方法推理，请指定一个
*空字符串作为值，例如{@code@Bean（destroyMethod=“”）}。注意
*{@链接org.springframework.beans.工厂.DisposableBean}回调接口将
*然而，被检测到并调用相应的destroy方法：在其他
*{@code destroyMethod=“”}只影响自定义关闭/关闭方法和
*{@链接java.io.可关闭}/{@链接java.lang.AutoCloseable（自动关闭）}声明的close方法。
*
注意：仅在生命周期由
*工厂，这通常是单例，但不保证任何
*其他范围。
*@看到了吗org.springframework.beans.工厂.DisposableBean
*@看到了吗org.springframework.context.ConfigurableApplicationContext#关闭（）
*/
String destroyMethod() default AbstractBeanDefinition.INFER_METHOD;
}
@Scope
注解在类上，描述spring容器如何创建Bean实例。
- singleton： 表示在spring容器中的单例，通过spring容器获得该bean时总是返回唯一的实例
- prototype：表示每次获得bean都会生成一个新的对象
- request：表示在一次http请求内有效（只适用于web应用）
- session：表示在一个用户会话内有效（只适用于web应用）
- globalSession：表示在全局会话内有效（只适用于web应用）
在多数情况，我们只会使用singleton和prototype两种scope，如果未指定scope属性，默认为singleton
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Scope {
/**
* Alias for {@link #scopeName}.
* @see #scopeName
*{@link#scopeName}的别名。
*@请参见#scopeName
*/
@AliasFor("scopeName")
String value() default "";
/**
* Specifies the name of the scope to use for the annotated component/bean.
* Defaults to an empty string ({@code ""}) which implies
* {@link ConfigurableBeanFactory#SCOPE_SINGLETON SCOPE_SINGLETON}.
* @since 4.2
* @see ConfigurableBeanFactory#SCOPE_PROTOTYPE
* @see ConfigurableBeanFactory#SCOPE_SINGLETON
* @see org.springframework.web.context.WebApplicationContext#SCOPE_REQUEST
* @see org.springframework.web.context.WebApplicationContext#SCOPE_SESSION
* @see #value
*指定要用于带注释的组件/bean的作用域的名称。
*
默认为空字符串（{@code“”}），这意味着
*{@link ConfigurableBeanFactory#SCOPE_SINGLETON SCOPE_SINGLETON}。
*@从4.2开始
*@请参阅ConfigurableBeanFactory#范围#原型
*@请参阅ConfigurableBeanFactory#SCOPE_SINGLETON
*@看到了吗org.springframework.web.context.WebApplicationContext#作用域请求
*@看到了吗org.springframework.web.应用上下文
*@见#值
*/
@AliasFor("value")
String scopeName() default "";
/**
* Specifies whether a component should be configured as a scoped proxy
* and if so, whether the proxy should be interface-based or subclass-based.
* Defaults to {@link ScopedProxyMode#DEFAULT}, which typically indicates
* that no scoped proxy should be created unless a different default
* has been configured at the component-scan instruction level.
*
Analogous to {@code
默认为{@link scopedProxy模式#DEFAULT}，这通常表示
*除非有不同的默认值，否则不应创建作用域代理
*已在组件扫描指令级别配置。
*
类似于{@代码<作用域代理/>}支持springxml。
*@请参阅scopedProxy模式
*/
ScopedProxyMode proxyMode() default ScopedProxyMode.DEFAULT;
}
@Configuration
标注当前类是配置类，并会将当前类内声明的一个或多个以@Bean注解标记的方法的实例纳入到srping容器中，并且实例名就是方法名。（其实就是靠@Component注解）
/*
* Copyright 2002-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.context.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.annotation.AliasFor;
import org.springframework.stereotype.Component;
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Configuration {
/**
* Explicitly specify the name of the Spring bean definition associated with the
* {@code @Configuration} class. If left unspecified (the common case), a bean
* name will be automatically generated.
* The custom name applies only if the {@code @Configuration} class is picked
* up via component scanning or supplied directly to an
* {@link AnnotationConfigApplicationContext}. If the {@code @Configuration} class
* is registered as a traditional XML bean definition, the name/id of the bean
* element will take precedence.
* @return the explicit component name, if any (or empty String otherwise)
* @see AnnotationBeanNameGenerator
*显式地指定与
*{@code@Configuration}类。如果未指定（常见情况），则为bean
*名称将自动生成。
*
自定义名称仅适用于{@code@Configuration}类
*通过组件扫描或直接提供给
*{@link AnnotationConfigApplicationContext}。如果{@code@Configuration}类
*注册为传统的xmlbean定义，即bean的名称/id
*元素将优先。
*@返回显式组件名，如果有（否则返回空字符串）
*@请参阅AnnotationBeanNameGenerator
*/
@AliasFor(annotation = Component.class)
String value() default "";
/**
* Specify whether {@code @Bean} methods should get proxied in order to enforce
* bean lifecycle behavior, e.g. to return shared singleton bean instances even
* in case of direct {@code @Bean} method calls in user code. This feature
* requires method interception, implemented through a runtime-generated CGLIB
* subclass which comes with limitations such as the configuration class and
* its methods not being allowed to declare {@code final}.
* The default is {@code true}, allowing for 'inter-bean references' via direct
* method calls within the configuration class as well as for external calls to
* this configuration's {@code @Bean} methods, e.g. from another configuration class.
* If this is not needed since each of this particular configuration's {@code @Bean}
* methods is self-contained and designed as a plain factory method for container use,
* switch this flag to {@code false} in order to avoid CGLIB subclass processing.
*
Turning off bean method interception effectively processes {@code @Bean}
* methods individually like when declared on non-{@code @Configuration} classes,
* a.k.a. "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore
* behaviorally equivalent to removing the {@code @Configuration} stereotype.
* @since 5.2
*指定{@code@Bean}方法是否应该被代理以便强制执行
*bean生命周期行为，例如返回共享的单例bean实例
*如果在用户代码中直接调用{@code@Bean}方法。此功能
*需要方法拦截，通过运行时生成的CGLIB实现
*子类，它具有诸如配置类和
*它的方法不允许声明{@code final}。
*
默认值是{@code true}，允许通过direct进行“bean间引用”
*方法调用以及外部调用
*这个配置的{@code@Bean}方法，例如来自另一个配置类。
*如果由于每个特定配置的{@code@Bean}而不需要这样做
*方法是独立的，设计为容器使用的普通工厂方法，
*将此标志切换为{@code false}，以避免处理CGLIB子类。
*
关闭bean方法拦截可以有效地处理{@code@bean}
*方法单独声明，比如在非{@code@Configuration}类上声明时，
*又称“@BeanLite模式”（参见{@linkbean@Bean的javadoc}）。因此是的
*行为上等同于移除{@code@Configuration}原型。
*@从5.2开始
*/
boolean proxyBeanMethods() default true;
}
@ConfigurationProperties
将配置文件中的参数映射成一个对象，通过prefix来设定前缀，然后将后面的和对象的属性名一致就能实现注入（当然这个对象需要注入的属性需要提供get和set方法 - - - 因为spring底层其实就是通过反射调用该对象的set方法）
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ConfigurationProperties {
/**
* The prefix of the properties that are valid to bind to this object. Synonym for
* {@link #prefix()}. A valid prefix is defined by one or more words separated with
* dots (e.g. {@code "acme.system.feature"}).
* @return the prefix of the properties to bind
*可绑定到此对象的有效属性的前缀。同义词
*{@link#prefix（）}。有效前缀由一个或多个用分隔的单词定义
*点（例如{@code“顶点.system.feature"}).
*@返回要绑定的属性的前缀
*/
@AliasFor("prefix")
String value() default "";
/**
* The prefix of the properties that are valid to bind to this object. Synonym for
* {@link #value()}. A valid prefix is defined by one or more words separated with
* dots (e.g. {@code "acme.system.feature"}).
* @return the prefix of the properties to bind
*可绑定到此对象的有效属性的前缀。同义词
*{@link#value（）}。有效前缀由一个或多个用分隔的单词定义
*点（例如{@code“顶点.system.feature"}).
*@返回要绑定的属性的前缀
*/
@AliasFor("value")
String prefix() default "";
/**
* Flag to indicate that when binding to this object invalid fields should be ignored.
* Invalid means invalid according to the binder that is used, and usually this means
* fields of the wrong type (or that cannot be coerced into the correct type).
* @return the flag value (default false)
*指示绑定到此对象时应忽略无效字段的标志。
*无效是指根据所使用的活页夹无效，通常这意味着
*类型错误的字段（或无法强制转换为正确类型的字段）。
*@返回标志值（默认为false）
*/
boolean ignoreInvalidFields() default false;
/**
* Flag to indicate that when binding to this object unknown fields should be ignored.
* An unknown field could be a sign of a mistake in the Properties.
* @return the flag value (default true)
*指示绑定到此对象时应忽略未知字段的标志。
*未知字段可能表示属性中存在错误。
*@返回标志值（默认为true）
*/
boolean ignoreUnknownFields() default true;
}
@Value
value的作用其实和ConfigurationProperties作用差不多，就是读取配置文件中参数的值，但是value是放在变量上面的，且是单值读取，还有一点就是value标注的变量并不需要和配置文件的参数名字一致。
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Value {
/**
* The actual value expression — for example, #{systemProperties.myProp}.
* 实际值表达式&mdash；例如，#{系统属性.myProp}。
*/
String value();
}
@Controller
用于标记在一个类上，使用它标记的类就是一个SpringMVC Controller 对象。
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
* @return the suggested component name, if any (or empty String otherwise)
*该值可能表示逻辑组件名称的建议，
*在自动检测到组件的情况下转换为springbean。
*@返回建议的组件名称（如果有）（否则返回空字符串）
*/
@AliasFor(annotation = Component.class)
String value() default "";
}
@Service
用于标记在一个类上，使用它标记的类就是一个SpringMVC Service 对象。
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
* @return the suggested component name, if any (or empty String otherwise)
*该值可能表示逻辑组件名称的建议，
*在自动检测到组件的情况下转换为springbean。
*@返回建议的组件名称（如果有）（否则返回空字符串）
*/
@AliasFor(annotation = Component.class)
String value() default "";
}
@Repository
用于标记在一个类上，使用它标记的类就是一个SpringMVC Repository对象。
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Controller {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
* @return the suggested component name, if any (or empty String otherwise)
*该值可能表示逻辑组件名称的建议，
*在自动检测到组件的情况下转换为springbean。
*@返回建议的组件名称（如果有）（否则返回空字符串）
*/
@AliasFor(annotation = Component.class)
String value() default "";
}
@RestController
一个组合注解，写在类上面，是组合了@ResponseBody和@Controller，默认了类中所有的方法都包含ResponseBody注解的一种简写形式
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Controller
@ResponseBody
public @interface RestController {
/**
* The value may indicate a suggestion for a logical component name,
* to be turned into a Spring bean in case of an autodetected component.
* @return the suggested component name, if any (or empty String otherwise)
* @since 4.0.1
*该值可能表示逻辑组件名称的建议，
*在自动检测到组件的情况下转换为springbean。
*@返回建议的组件名称（如果有）（否则返回空字符串）
*@从4.0.1开始
*/
@AliasFor(annotation = Controller.class)
String value() default "";
}
@Resource
是按照名称来注入的，当找不到与名称匹配的bean才会按照类型来注入。其实我们平时用的@Resource都是用了他的默认的方式，即都不指定名字和类型。spring通过反射机制使用byName方法自动注入。
@Target({TYPE, FIELD, METHOD}) @Retention(RUNTIME) public @interface Resource { /** * The JNDI name of the resource. For field annotations, * the default is the field name. For method annotations, * the default is the JavaBeans property name corresponding * to the method. For class annotations, there is no default * and this must be specified. *资源的JNDI名称。对于字段注释， *默认为字段名。对于方法注释， *默认值是对应的JavaBeans属性名 *方法。对于类注释，没有默认值 *必须指定这一点。 */ String name() default ""; /** * The name of the resource that the reference points to. It can * link to any compatible resource using the global JNDI names. * * @since Common Annotations 1.1 *引用指向的资源的名称。它可以 *使用全局JNDI名称链接到任何兼容资源。 * *@since Common Annotations 1.1版之后 */ String lookup() default ""; /** * The Java type of the resource. For field annotations, * the default is the type of the field. For method annotations, * the default is the type of the JavaBeans property. * For class annotations, there is no default and this must be * specified. *资源的Java类型。对于字段注释， *默认为字段的类型。对于方法注释， *默认值是JavaBeans属性的类型。 *对于类注释，没有默认值，这必须是 *指定的。 */ Class<?> type() default java.lang.Object.class; /** * The two possible authentication types for a resource. */ enum AuthenticationType { CONTAINER, APPLICATION } /** * The authentication type to use for this resource. * This may be specified for resources representing a * connection factory of any supported type, and must * not be specified for resources of other types. *用于此资源的身份验证类型。 *可以为表示 *任何支持类型的连接工厂，并且必须 *不能为其他类型的资源指定。 */ AuthenticationType authenticationType() default AuthenticationType.CONTAINER; /** * Indicates whether this resource can be shared between * this component and other components. * This may be specified for resources representing a * connection factory of any supported type, and must * not be specified for resources of other types. *指示此资源是否可以在 *此组件和其他组件。 *可以为表示 *任何支持类型的连接工厂，并且必须 *不能为其他类型的资源指定。 */ boolean shareable() default true; /** * A product specific name that this resource should be mapped to. * The name of this resource, as defined by the命名空间）许多应用程序服务器 *提供一种将这些本地名称映射到资源名称的方法 *应用程序服务器已知。此映射名称通常是 *全局JNDI名称，但可以是任何形式的名称。name* element or defaulted, is a name that is local to the application * component using the resource. (It's a name in the JNDI *java:comp/envnamespace.) Many application servers * provide a way to map these local names to names of resources * known to the application server. This mapped name is often a * global JNDI name, but may be a name of any form.* * Application servers are not required to support any particular * form or type of mapped name, nor the ability to use mapped names. * The mapped name is product-dependent and often installation-dependent. * No use of a mapped name is portable. *此资源应映射到的产品特定名称。 *此资源的名称，由
名称定义 *元素或默认值，是应用程序的本地名称 *使用资源的组件。（这是JNDI中的一个名字 *<代码>java：组件/环境在 * *应用服务器不需要支持任何特定的 *映射名称的形式或类型，也不能使用映射名称。 *映射的名称取决于产品，通常取决于安装。 *映射名称的使用是不可移植的。 */ String mappedName() default ""; /** * Description of this resource. The description is expected * to be in the default language of the system on which the * application is deployed. The description can be presented * to the Deployer to help in choosing the correct resource. *此资源的说明。需要说明 *使用系统的默认语言 *应用程序已部署。描述可以呈现 *以帮助部署人员选择正确的资源。 */ String description() default ""; }
@Resource 的装配顺序：
- 如果同时指定了 name 属性和 type 属性，那么 Spring 将从容器中找唯一匹配的 bean 进行装配，找不到则抛出异常
- 如果指定了 name 属性值，则从容器中查找名称匹配的 bean 进行装配，找不到则抛出异常
- 如果指定了 type 属性值，则从容器中查找类型匹配的唯一的 bean 进行装配，找不到或者找到多个都会抛出异常
- 如果都不指定，则会自动按照 byName 方式进行装配（我们一般都用的是这个。。。）
@Autowried
默认是按照类型进行装配注入，如果允许 null 值，可以设置它 required 为false。即：当不能确定 Spring 容器中一定拥有某个类的 Bean 时，可以在需要自动注入该类 Bean 的地方可以使用 @Autowired(required = false) ，这等于告诉 Spring：在找不到匹配 Bean 时也不报错。
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
/**
* Declares whether the annotated dependency is required.
* Defaults to {@code true}.
*声明是否需要带注释的依赖项。
*
默认为{@code true}。
*/
boolean required() default true;
}
@Qualifier
@Autowired是根据类型进行自动装配的。如果当spring上下文中存在不止一个A类型的bean时，就会抛出BeanCreationException异常;如果Spring上下文中不存在A类型的bean，而且我们又使用A类型，也会抛出BeanCreationException异常。针对存在多个A类型的Bean，我们可以联合使用@Qualifier和@Autowired来解决这些问题。
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.TYPE, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface Qualifier {
String value() default "";
}
@SpringBootConfiguration
说明这是一个配置文件类，就像xml配置文件，而现在是用java配置文件。并会将当前类内声明的一个或多个以@Bean注解标记的方法的实例纳入到spring容器中，并且实例名就是方法名。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Configuration
public @interface SpringBootConfiguration {
/**
* Specify whether {@link Bean @Bean} methods should get proxied in order to enforce
* bean lifecycle behavior, e.g. to return shared singleton bean instances even in
* case of direct {@code @Bean} method calls in user code. This feature requires
* method interception, implemented through a runtime-generated CGLIB subclass which
* comes with limitations such as the configuration class and its methods not being
* allowed to declare {@code final}.
*
* The default is {@code true}, allowing for 'inter-bean references' within the
* configuration class as well as for external calls to this configuration's
* {@code @Bean} methods, e.g. from another configuration class. If this is not needed
* since each of this particular configuration's {@code @Bean} methods is
* self-contained and designed as a plain factory method for container use, switch
* this flag to {@code false} in order to avoid CGLIB subclass processing.
*
* Turning off bean method interception effectively processes {@code @Bean} methods
* individually like when declared on non-{@code @Configuration} classes, a.k.a.
* "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore behaviorally
* equivalent to removing the {@code @Configuration} stereotype.
* @return whether to proxy {@code @Bean} methods
* @since 2.2
*指定{@linkbean@Bean}方法是否应该被代理以便强制执行
*bean生命周期行为，例如，即使在
*用户代码中直接调用{@code@Bean}方法的情况。此功能需要
*方法拦截，通过运行时生成的CGLIB子类实现
*会带来一些限制，比如配置类及其方法
*允许声明{@code final}。
*
*默认值是{@codetrue}，允许在
*配置类以及对此配置的外部调用
*{@code@Bean}方法，例如来自另一个配置类。如果不需要的话
*因为每个特定配置的{@code@Bean}方法都是
*独立的，设计成一种简单的工厂方法，用于集装箱、开关
*将此标志设置为{@code false}，以避免处理CGLIB子类。
*
*关闭bean方法拦截可以有效地处理{@code@bean}方法
*比如在非{@code@Configuration}类上声明时，也就是说。
*“@BeanLite模式”（参见{@linkbean@Bean的javadoc}）。因此，行为是口头的
*相当于删除{@code@Configuration}原型。
*@return是否代理{@code@Bean}方法
*@从2.2开始
*/
@AliasFor(annotation = Configuration.class)
boolean proxyBeanMethods() default true;
}
@EnableAutoConfiguration
表示开启自动配置，我们平时所说springboot无配置就是这个参数起的作用，他读取了springboot默认的配置。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(AutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {
String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";
/**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*排除特定的自动配置类，使其永远不会被应用。
*@返回要排除的类
*/
Class<?>[] exclude() default {};
/**
* Exclude specific auto-configuration class names such that they will never be
* applied.
* @return the class names to exclude
* @since 1.3.0
*排除特定的自动配置类名，使它们永远不会
*应用。
*@返回要排除的类名
*@自1.3.0起
*/
String[] excludeName() default {};
}
@ComponentScan
表示自动扫描，这个扫描默认只能扫同一级的目录。
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
@Repeatable(ComponentScans.class)
public @interface ComponentScan {
/**
* Alias for {@link #basePackages}.
* Allows for more concise annotation declarations if no other attributes
* are needed — for example, {@code @ComponentScan("org.my.pkg")}
* instead of {@code @ComponentScan(basePackages = "org.my.pkg")}.
*{@link#basePackages}的别名。
*
如果没有其他属性，则允许更简洁的注释声明
*例如，{@code@ComponentScan（“org.my.pkg.软件包")}
*而不是{@code@ComponentScan（basePackages=”org.my.pkg.软件包")}.
*/
@AliasFor("basePackages")
String[] value() default {};
/**
* Base packages to scan for annotated components.
* {@link #value} is an alias for (and mutually exclusive with) this
* attribute.
*
Use {@link #basePackageClasses} for a type-safe alternative to
* String-based package names.
*扫描带注释组件的基本包。
*
{@link#value}是此的别名（与互斥）
*属性。
*
使用{@link#basePackageClasses}作为
*基于字符串的包名称。
*/
@AliasFor("value")
String[] basePackages() default {};
/**
* Type-safe alternative to {@link #basePackages} for specifying the packages
* to scan for annotated components. The package of each class specified will be scanned.
* Consider creating a special no-op marker class or interface in each package
* that serves no purpose other than being referenced by this attribute.
*用于指定包的{@link#basePackages}的类型安全替代方法
*扫描带注释的组件。将扫描指定的每个类的包。
*
考虑在每个包中创建一个特殊的no-op标记类或接口
*它除了被此属性引用之外没有其他用途。
*/
Class<?>[] basePackageClasses() default {};
/**
* The {@link BeanNameGenerator} class to be used for naming detected components
* within the Spring container.
* The default value of the {@link BeanNameGenerator} interface itself indicates
* that the scanner used to process this {@code @ComponentScan} annotation should
* use its inherited bean name generator, e.g. the default
* {@link AnnotationBeanNameGenerator} or any custom instance supplied to the
* application context at bootstrap time.
* @see AnnotationConfigApplicationContext#setBeanNameGenerator(BeanNameGenerator)
* @see AnnotationBeanNameGenerator
* @see FullyQualifiedAnnotationBeanNameGenerator
*用于命名检测到的组件的{@link BeanNameGenerator}类
*在弹簧容器内。
*
{@link beannamGenerator}接口本身的默认值表示
*用于处理此{@code@ComponentScan}注释的扫描仪应该
*使用它继承的bean名称生成器，例如默认的
*{@link AnnotationBeanNameGenerator}或提供给
*引导时的应用程序上下文。
*@请参阅AnnotationConfigApplicationContext\setBeanNameGenerator（BeanNameGenerator）
*@请参阅AnnotationBeanNameGenerator
*@查看完全合格的注释
*/
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
/**
* The {@link ScopeMetadataResolver} to be used for resolving the scope of detected components.
*用于解析检测到的组件范围的{@link ScopeMetadataResolver}。
*/
Class<? extends ScopeMetadataResolver> scopeResolver() default AnnotationScopeMetadataResolver.class;
/**
* Indicates whether proxies should be generated for detected components, which may be
* necessary when using scopes in a proxy-style fashion.
* The default is defer to the default behavior of the component scanner used to
* execute the actual scan.
*
Note that setting this attribute overrides any value set for {@link #scopeResolver}.
* @see ClassPathBeanDefinitionScanner#setScopedProxyMode(ScopedProxyMode)
*指示是否应为检测到的组件生成代理，这可能是
*以代理样式方式使用作用域时必需。
*
默认值是根据组件扫描程序的默认行为
*执行实际扫描。
*
请注意，设置此属性会覆盖为{@link#scopeResolver}设置的任何值。
*@see ClassPathBeanDefinitionScanner\setScopedProxyMode（ScopedProxyMode）
*/
ScopedProxyMode scopedProxy() default ScopedProxyMode.DEFAULT;
/**
* Controls the class files eligible for component detection.
* Consider use of {@link #includeFilters} and {@link #excludeFilters}
* for a more flexible approach.
*控制符合组件检测条件的类文件。
*
考虑使用{@link#includeFilters}和{@link\#excludeFilters}
*更灵活的方法。
*/
String resourcePattern() default ClassPathScanningCandidateComponentProvider.DEFAULT_RESOURCE_PATTERN;
/**
* Indicates whether automatic detection of classes annotated with {@code @Component}
* {@code @Repository}, {@code @Service}, or {@code @Controller} should be enabled.
*指示是否自动检测用{@code@Component}注释的类
*应启用{@code@Repository}、{@code@Service}或{@code@Controller}。
*/
boolean useDefaultFilters() default true;
/**
* Specifies which types are eligible for component scanning.
* Further narrows the set of candidate components from everything in {@link #basePackages}
* to everything in the base packages that matches the given filter or filters.
*
Note that these filters will be applied in addition to the default filters, if specified.
* Any type under the specified base packages which matches a given filter will be included,
* even if it does not match the default filters (i.e. is not annotated with {@code @Component}).
* @see #resourcePattern()
* @see #useDefaultFilters()
*指定哪些类型有资格进行组件扫描。
*
进一步缩小{@link#basePackages}中的所有候选组件集
*与给定筛选器匹配的基包中的所有内容。
*
请注意，如果指定了这些过滤器，那么除了默认过滤器之外，还将应用这些过滤器。
*将包括指定基包下与给定筛选器匹配的任何类型，
*即使它与默认过滤器不匹配（即没有用{@code@Component}注释）。
*@请参阅资源模式（）
*@请参见#useDefaultFilters（）
*/
Filter[] includeFilters() default {};
/**
* Specifies which types are not eligible for component scanning.
* @see #resourcePattern
*指定哪些类型不适合组件扫描。
*@see资源模式
*/
Filter[] excludeFilters() default {};
/**
* Specify whether scanned beans should be registered for lazy initialization.
* Default is {@code false}; switch this to {@code true} when desired.
* @since 4.1
*指定是否应为延迟初始化注册扫描的bean。
*
默认值是{@code false}；如果需要，将其切换到{@code true}。
*@从4.1开始
*/
boolean lazyInit() default false;
/**
* Declares the type filter to be used as an {@linkplain ComponentScan#includeFilters
* include filter} or {@linkplain ComponentScan#excludeFilters exclude filter}.
*声明要用作{@linkplain ComponentScan\includeFilter的类型筛选器
*include filter}或{@linkplain ComponentScan#excludeFilters排除筛选器}。
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({})
@interface Filter {
/**
* The type of filter to use.
* Default is {@link FilterType#ANNOTATION}.
* @see #classes
* @see #pattern
*要使用的筛选器类型。
*
默认值是{@link FilterType\#ANNOTATION}。
*@查看课程
*@见#图案
*/
FilterType type() default FilterType.ANNOTATION;
/**
* Alias for {@link #classes}.
* @see #classes
*{@link#classes}的别名。
*@查看课程
*/
@AliasFor("classes")
Class<?>[] value() default {};
/**
* The class or classes to use as the filter.
* The following table explains how the classes will be interpreted
* based on the configured value of the {@link #type} attribute.
*
* {@code FilterType} Class Interpreted As {@link FilterType#ANNOTATION ANNOTATION}
* the annotation itself {@link FilterType#ASSIGNABLE_TYPE ASSIGNABLE_TYPE}
* the type that detected components should be assignable to {@link FilterType#CUSTOM CUSTOM}
* an implementation of {@link TypeFilter}
* When multiple classes are specified, OR logic is applied
* — for example, "include types annotated with {@code @Foo} OR {@code @Bar}".
*
Custom {@link TypeFilter TypeFilters} may optionally implement any of the
* following {@link org.springframework.beans.factory.Aware Aware} interfaces, and
* their respective methods will be called prior to {@link TypeFilter#match match}:
*
* - {@link org.springframework.context.EnvironmentAware EnvironmentAware}
* - {@link org.springframework.beans.factory.BeanFactoryAware BeanFactoryAware}
*
- {@link org.springframework.beans.factory.BeanClassLoaderAware BeanClassLoaderAware}
*
- {@link org.springframework.context.ResourceLoaderAware ResourceLoaderAware}
*
* Specifying zero classes is permitted but will have no effect on component
* scanning.
* @since 4.2
* @see #value
* @see #type
*用作筛选器的一个或多个类。
*
下表说明了如何解释类
*基于{@link#type}属性的配置值。
*
*{@code FilterType} 类解释为 {@link FilterType注解注解}
*注释本身 {@link FilterType可分配类型可分配类型
*检测到的组件应分配给的类型 {@link FilterType#自定义}
*{@link TypeFilter}的实现
*
*当指定多个类时，或逻辑被应用
*例如，“包括用{@code@Foo}或{@code@Bar}注释的类型”。
*
自定义{@link TypeFilter TypeFilters}可以选择实现
*跟随{@linkorg.springframework.beans.工厂。知道吗Aware}接口，以及
*它们各自的方法将在{@link TypeFilter#match match}之前调用：
*
*- {@链接org.springframework.context.EnvironmentAware EnvironmentAware}
*- {@链接org.springframework.beans.factory.BeanFactoryAwareBeanFactoryAware}
*
- {@链接org.springframework.beans.factory.BeanClassLoaderwareBeanClassLoaderware}
*
- {@链接org.springframework.context.resourceLoaderware ResourceLoaderware}
*
*允许指定零类，但不会对组件产生影响
*正在扫描。
*@从4.2开始
*@见#值
*@见#类型
*/
@AliasFor("value")
Class<?>[] classes() default {};
/**
* The pattern (or patterns) to use for the filter, as an alternative
* to specifying a Class {@link #value}.
* If {@link #type} is set to {@link FilterType#ASPECTJ ASPECTJ},
* this is an AspectJ type pattern expression. If {@link #type} is
* set to {@link FilterType#REGEX REGEX}, this is a regex pattern
* for the fully-qualified class names to match.
* @see #type
* @see #classes
*作为替代方案，用于筛选器的一个或多个模式
*指定一个类{@link#value}。
*
如果{@link#type}设置为{@link FilterType#ASPECTJ ASPECTJ}，
*这是一个AspectJ类型模式表达式。如果{@link#type}是
*设置为{@link FilterType#REGEX REGEX}，这是一个REGEX模式
*以匹配完全限定类名。
*@见#类型
*@查看课程
*/
String[] pattern() default {};
}
}
@SpringBootApplication
这个注解就是集成了：@SpringBootConfiguration、@EnableAutoConfiguration、@ComponentScan这三个注解。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan(excludeFilters = { @Filter(type = FilterType.CUSTOM, classes = TypeExcludeFilter.class),
@Filter(type = FilterType.CUSTOM, classes = AutoConfigurationExcludeFilter.class) })
public @interface SpringBootApplication {
/**
* Exclude specific auto-configuration classes such that they will never be applied.
* @return the classes to exclude
*排除特定的自动配置类，使其永远不会被应用。
*@返回要排除的类
*/
@AliasFor(annotation = EnableAutoConfiguration.class)
Class<?>[] exclude() default {};
/**
* Exclude specific auto-configuration class names such that they will never be
* applied.
* @return the class names to exclude
* @since 1.3.0
*排除特定的自动配置类名，使它们永远不会
*应用。
*@返回要排除的类名
*@自1.3.0起
*/
@AliasFor(annotation = EnableAutoConfiguration.class)
String[] excludeName() default {};
/**
* Base packages to scan for annotated components. Use {@link #scanBasePackageClasses}
* for a type-safe alternative to String-based package names.
*
* Note: this setting is an alias for
* {@link ComponentScan @ComponentScan} only. It has no effect on {@code @Entity}
* scanning or Spring Data {@link Repository} scanning. For those you should add
* {@link org.springframework.boot.autoconfigure.domain.EntityScan @EntityScan} and
* {@code @Enable...Repositories} annotations.
* @return base packages to scan
* @since 1.3.0
*扫描带注释组件的基本包。使用{@link#scanBasePackageClasses}
*作为基于字符串的包名的类型安全替代项。
*
*注意：此设置是的别名
*{@link ComponentScan@ComponentScan}仅限。它对{@code@Entity}没有影响
*扫描或Spring数据{@link Repository}扫描。对于那些你应该补充的
*{@链接org.springframework.boot.自动配置.domain.EntityScan@EntityScan}和
*{@code@Enable…Repositories}注释。
*@返回要扫描的基本包
*@自1.3.0起
*/
@AliasFor(annotation = ComponentScan.class, attribute = "basePackages")
String[] scanBasePackages() default {};
/**
* Type-safe alternative to {@link #scanBasePackages} for specifying the packages to
* scan for annotated components. The package of each class specified will be scanned.
*
* Consider creating a special no-op marker class or interface in each package that
* serves no purpose other than being referenced by this attribute.
*
* Note: this setting is an alias for
* {@link ComponentScan @ComponentScan} only. It has no effect on {@code @Entity}
* scanning or Spring Data {@link Repository} scanning. For those you should add
* {@link org.springframework.boot.autoconfigure.domain.EntityScan @EntityScan} and
* {@code @Enable...Repositories} annotations.
* @return base packages to scan
* @since 1.3.0
*键入{@link#scanBasePackages}的安全替代方法，用于将包指定给
*扫描带注释的组件。将扫描指定的每个类的包。
*
*考虑在每个包中创建一个特殊的no-op标记类或接口
*除了被此属性引用外，没有其他用途。
*
*注意：此设置是的别名
*{@link ComponentScan@ComponentScan}仅限。它对{@code@Entity}没有影响
*扫描或Spring数据{@link Repository}扫描。对于那些你应该补充的
*{@链接org.springframework.boot.自动配置.domain.EntityScan@EntityScan}和
*{@code@Enable…Repositories}注释。
*@返回要扫描的基本包
*@自1.3.0起
*/
@AliasFor(annotation = ComponentScan.class, attribute = "basePackageClasses")
Class<?>[] scanBasePackageClasses() default {};
/**
* The {@link BeanNameGenerator} class to be used for naming detected components
* within the Spring container.
*
* The default value of the {@link BeanNameGenerator} interface itself indicates that
* the scanner used to process this {@code @SpringBootApplication} annotation should
* use its inherited bean name generator, e.g. the default
* {@link AnnotationBeanNameGenerator} or any custom instance supplied to the
* application context at bootstrap time.
* @return {@link BeanNameGenerator} to use
* @see SpringApplication#setBeanNameGenerator(BeanNameGenerator)
* @since 2.3.0
*用于命名检测到的组件的{@link BeanNameGenerator}类
*在弹簧容器内。
*
*{@link beannamGenerator}接口本身的默认值表明
*用于处理{@code@SpringBootApplication}注释的扫描仪应该
*使用它继承的bean名称生成器，例如默认的
*{@link AnnotationBeanNameGenerator}或提供给
*引导时的应用程序上下文。
*@return{@link BeanNameGenerator}使用
*@see SpringApplication设置名称生成器（BeanNameGenerator）
*@从2.3.0开始
*/
@AliasFor(annotation = ComponentScan.class, attribute = "nameGenerator")
Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
/**
* Specify whether {@link Bean @Bean} methods should get proxied in order to enforce
* bean lifecycle behavior, e.g. to return shared singleton bean instances even in
* case of direct {@code @Bean} method calls in user code. This feature requires
* method interception, implemented through a runtime-generated CGLIB subclass which
* comes with limitations such as the configuration class and its methods not being
* allowed to declare {@code final}.
*
* The default is {@code true}, allowing for 'inter-bean references' within the
* configuration class as well as for external calls to this configuration's
* {@code @Bean} methods, e.g. from another configuration class. If this is not needed
* since each of this particular configuration's {@code @Bean} methods is
* self-contained and designed as a plain factory method for container use, switch
* this flag to {@code false} in order to avoid CGLIB subclass processing.
*
* Turning off bean method interception effectively processes {@code @Bean} methods
* individually like when declared on non-{@code @Configuration} classes, a.k.a.
* "@Bean Lite Mode" (see {@link Bean @Bean's javadoc}). It is therefore behaviorally
* equivalent to removing the {@code @Configuration} stereotype.
* @since 2.2
* @return whether to proxy {@code @Bean} methods
*指定{@linkbean@Bean}方法是否应该被代理以便强制执行
*bean生命周期行为，例如，即使在
*用户代码中直接调用{@code@Bean}方法的情况。此功能需要
*方法拦截，通过运行时生成的CGLIB子类实现
*会带来一些限制，比如配置类及其方法
*允许声明{@code final}。
*
*默认值是{@codetrue}，允许在
*配置类以及对此配置的外部调用
*{@code@Bean}方法，例如来自另一个配置类。如果不需要的话
*因为每个特定配置的{@code@Bean}方法都是
*独立的，设计成一种简单的工厂方法，用于集装箱、开关
*将此标志设置为{@code false}，以避免处理CGLIB子类。
*
*关闭bean方法拦截可以有效地处理{@code@bean}方法
*比如在非{@code@Configuration}类上声明时，也就是说。
*“@BeanLite模式”（参见{@linkbean@Bean的javadoc}）。因此，行为是口头的
*相当于删除{@code@Configuration}原型。
*@从2.2开始
*@return是否代理{@code@Bean}方法
*/
@AliasFor(annotation = Configuration.class)
boolean proxyBeanMethods() default true;
}
@EnableConfigurationProperties
将带有@ConfigurationProperties注解的类注入为Spring容器的Bean。如果使用了@ConfigurationProperties但是没有在启动类上增加这个注解，则@ConfigurationProperties将不起作用。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(EnableConfigurationPropertiesRegistrar.class)
public @interface EnableConfigurationProperties {
/**
* The bean name of the configuration properties validator.
* @since 2.2.0
*配置属性验证器的bean名称。
*@从2.2.0开始
*/
String VALIDATOR_BEAN_NAME = "configurationPropertiesValidator";
/**
* Convenient way to quickly register
* {@link ConfigurationProperties @ConfigurationProperties} annotated beans with
* Spring. Standard Spring Beans will also be scanned regardless of this value.
* @return {@code @ConfigurationProperties} annotated beans to register
*快速注册的便捷方式
*{@link ConfigurationProperties@ConfigurationProperties}带注释的bean
*春天。不管这个值是多少，标准的springbean也将被扫描。
*@return{@code@ConfigurationProperties}要注册的带注释bean
*/
Class<?>[] value() default {};
}
@Async
表示这个方法为异步方法，@Async就相当于另起一个线程。
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Async {
/**
* A qualifier value for the specified asynchronous operation(s).
* May be used to determine the target executor to be used when executing
* the asynchronous operation(s), matching the qualifier value (or the bean
* name) of a specific {@link java.util.concurrent.Executor Executor} or
* {@link org.springframework.core.task.TaskExecutor TaskExecutor}
* bean definition.
*
When specified on a class-level {@code @Async} annotation, indicates that the
* given executor should be used for all methods within the class. Method-level use
* of {@code Async#value} always overrides any value set at the class level.
* @since 3.1.2
*指定的异步操作的限定符值。
*
可用于确定执行时要使用的目标执行器
*与限定符值（或bean）匹配的异步操作
*一个特定的{@link的名称）java.util.concurrent.Executor Executor}或
*{@链接org.springframework.core.任务.任务执行器任务执行者}
*bean定义。
*
在类级别{@code@Async}注释上指定时，表示
*给定的执行器应该用于类中的所有方法。方法级使用
*of{@code Async#value}始终重写类级别上设置的任何值。
*@从3.1.2开始
*/
String value() default "";
}
@EnableAsync
这个注解需要加在启动类上，表示支持异步操作；如果不加，则@Async将不起作用。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AsyncConfigurationSelector.class)
public @interface EnableAsync {
/**
* Indicate the 'async' annotation type to be detected at either class
* or method level.
* By default, both Spring's @{@link Async} annotation and the EJB 3.1
* {@code @javax.ejb.Asynchronous} annotation will be detected.
*
This attribute exists so that developers can provide their own
* custom annotation type to indicate that a method (or all methods of
* a given class) should be invoked asynchronously.
*指示要在任一类中检测的“async”批注类型
*或方法级别。
*
默认情况下，Spring的@{@link Async}注释和ejb3.1
*{@代码@javax.ejb.异步}将检测到批注。
*
此属性的存在使得开发人员可以提供自己的
*自定义批注类型，以指示方法（或
*应异步调用。
*/
Class<? extends Annotation> annotation() default Annotation.class;
/**
* Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
* to standard Java interface-based proxies.
* Applicable only if the {@link #mode} is set to {@link AdviceMode#PROXY}.
*
The default is {@code false}.
*
Note that setting this attribute to {@code true} will affect all
* Spring-managed beans requiring proxying, not just those marked with {@code @Async}.
* For example, other beans marked with Spring's {@code @Transactional} annotation
* will be upgraded to subclass proxying at the same time. This approach has no
* negative impact in practice unless one is explicitly expecting one type of proxy
* vs. another — for example, in tests.
*指示是否相反地创建基于子类（CGLIB）的代理
*到标准的基于Java接口的代理。
*
仅当{@link#mode}设置为{@link AdviceMode}PROXY}时才适用。
*默认值是{@code false}。
*
请注意，将此属性设置为{@code true}将影响所有
*需要代理的Spring托管bean，而不仅仅是那些用{@code@Async}标记的bean。
*例如，用Spring的{@code@Transactional}注释标记的其他bean
*将同时升级到子类代理。这种方法没有
*在实践中的负面影响，除非明确要求一种类型的代理
*例如，在测试中。
*/
boolean proxyTargetClass() default false;
/**
* Indicate how async advice should be applied.
* The default is {@link AdviceMode#PROXY}.
* Please note that proxy mode allows for interception of calls through the proxy
* only. Local calls within the same class cannot get intercepted that way; an
* {@link Async} annotation on such a method within a local call will be ignored
* since Spring's interceptor does not even kick in for such a runtime scenario.
* For a more advanced mode of interception, consider switching this to
* {@link AdviceMode#ASPECTJ}.
*指示应如何应用异步建议。
*
默认值是{@link AdviceMode#PROXY}
*请注意，代理模式允许通过代理拦截呼叫
*只有。同一个类中的本地调用不能以这种方式被截获；一个
*本地调用中此类方法的{@link Async}注释将被忽略
*因为Spring的拦截器甚至不会在这样的运行时场景中启动。
*对于更高级的拦截模式，请考虑将其切换到
*{@link AdviceMode\ASPECTJ}。
*/
AdviceMode mode() default AdviceMode.PROXY;
/**
* Indicate the order in which the {@link AsyncAnnotationBeanPostProcessor}
* should be applied.
* The default is {@link Ordered#LOWEST_PRECEDENCE} in order to run
* after all other post-processors, so that it can add an advisor to
* existing proxies rather than double-proxy.
*指示{@link AsyncAnnotationBeanPostProcessor}的顺序
*应该应用。
*
为了运行，默认值是{@link Ordered#最低优先级}
*在所有其他后处理程序之后，以便它可以向
*现有代理而不是双代理。
*/
int order() default Ordered.LOWEST_PRECEDENCE;
}
@Scheduled
定时任务。
@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Repeatable(Schedules.class)
public @interface Scheduled {
/**
* A special cron expression value that indicates a disabled trigger: {@value}.
* This is primarily meant for use with ${...} placeholders,
* allowing for external disabling of corresponding scheduled methods.
* @since 5.1
* @see ScheduledTaskRegistrar#CRON_DISABLED
*一个特殊的cron表达式值，指示禁用的触发器：{@value}。
*
这主要用于${…}占位符，
*允许外部禁用相应的调度方法。
*@从5.1开始
*@see ScheduledTaskRegistrar\CRON#u禁用
*/
String CRON_DISABLED = ScheduledTaskRegistrar.CRON_DISABLED;
/**
* A cron-like expression, extending the usual UN*X definition to include triggers
* on the second, minute, hour, day of month, month, and day of week.
* For example, {@code "0 * * * * MON-FRI"} means once per minute on weekdays
* (at the top of the minute - the 0th second).
*
The fields read from left to right are interpreted as follows.
*
* - second
* - minute
* - hour
* - day of month
* - month
* - day of week
*
* The special value {@link #CRON_DISABLED "-"} indicates a disabled cron
* trigger, primarily meant for externally specified values resolved by a
* ${...} placeholder.
* @return an expression that can be parsed to a cron schedule
* @see org.springframework.scheduling.support.CronSequenceGenerator
*一个类似cron的表达式，扩展了通常的UN*X定义以包括触发器
*在秒、分、时、月、月、日。
*
例如，{@code“0****MON-FRI”}表示工作日每分钟一次
*（在分钟的顶部-第0秒）。
*
从左到右读取的字段解释如下。
*
*- 秒
*- 分钟
*- 小时
*- 月日
*- 月
*- 星期几
*
*特殊值{@link#CRON#DISABLED“-”}表示禁用的CRON
*触发器，主要用于由
*${…}占位符。
*@返回一个可以解析为cron计划的表达式
*@看到了吗org.springframework.scheduling.support.CronSequenceGenerator
*/
String cron() default "";
/**
* A time zone for which the cron expression will be resolved. By default, this
* attribute is the empty String (i.e. the server's local time zone will be used).
* @return a zone id accepted by {@link java.util.TimeZone#getTimeZone(String)},
* or an empty String to indicate the server's default time zone
* @since 4.0
* @see org.springframework.scheduling.support.CronTrigger#CronTrigger(String, java.util.TimeZone)
* @see java.util.TimeZone
*将为其解析cron表达式的时区。默认情况下
*属性是空字符串（即将使用服务器的本地时区）。
*@返回{@link接受的区域idjava.util.TimeZone#获取时区（字符串）}，
*或空字符串来指示服务器的默认时区
*@从4.0开始
*@看到了吗org.springframework.scheduling.支持.CronTrigger\CronTrigger（字符串，java.util.TimeZone)
*@看到了吗java.util.TimeZone
*/
String zone() default "";
/**
* Execute the annotated method with a fixed period in milliseconds between the
* end of the last invocation and the start of the next.
* @return the delay in milliseconds
*在
*上一次调用结束，下一次调用开始。
*@返回毫秒延迟
*/
long fixedDelay() default -1;
/**
* Execute the annotated method with a fixed period in milliseconds between the
* end of the last invocation and the start of the next.
* @return the delay in milliseconds as a String value, e.g. a placeholder
* or a {@link java.time.Duration#parse java.time.Duration} compliant value
* @since 3.2.2
*在
*上一次调用结束，下一次调用开始。
*@将延迟以毫秒为单位返回字符串值，例如占位符
*或{@链接java.time.Duration解析java.time.Duration.持续时间}合规价值
*@从3.2.2开始
*/
String fixedDelayString() default "";
/**
* Execute the annotated method with a fixed period in milliseconds between
* invocations.
* @return the period in milliseconds
*执行带注释的方法，其时间间隔为毫秒
*调用。
*@返回时间段（毫秒）
*/
long fixedRate() default -1;
/**
* Execute the annotated method with a fixed period in milliseconds between
* invocations.
* @return the period in milliseconds as a String value, e.g. a placeholder
* or a {@link java.time.Duration#parse java.time.Duration} compliant value
* @since 3.2.2
*执行带注释的方法，其时间间隔为毫秒
*调用。
*@返回以毫秒为单位的字符串值，例如占位符
*或{@链接java.time.Duration解析java.time.Duration.持续时间}合规价值
*@从3.2.2开始
*/
String fixedRateString() default "";
/**
* Number of milliseconds to delay before the first execution of a
* {@link #fixedRate} or {@link #fixedDelay} task.
* @return the initial delay in milliseconds
* @since 3.2
*在第一次执行之前要延迟的毫秒数
*{@link#fixedDate}或{@link#fixedDelay}任务。
*@返回初始延迟（毫秒）
*@从3.2开始
*/
long initialDelay() default -1;
/**
* Number of milliseconds to delay before the first execution of a
* {@link #fixedRate} or {@link #fixedDelay} task.
* @return the initial delay in milliseconds as a String value, e.g. a placeholder
* or a {@link java.time.Duration#parse java.time.Duration} compliant value
* @since 3.2.2
*在第一次执行之前要延迟的毫秒数
*{@link#fixedDate}或{@link#fixedDelay}任务。
*@以字符串值的形式返回初始延迟（毫秒），例如占位符
*或{@链接java.time.Duration解析java.time.Duration.持续时间}合规价值
*@从3.2.2开始
*/
String initialDelayString() default "";
}
@EnableScheduling
这个注解需要加在启动类上，表示支持定时任务。
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Import(SchedulingConfiguration.class)
@Documented
public @interface EnableScheduling {
}
@PathVariable
通过 @PathVariable 可以将 URL 中占位符参数绑定到控制器处理方法的入参中：URL 中的 {xxx} 占位符可以通过@PathVariable(“xxx“) 绑定到操作方法的入参中。
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface PathVariable {
/**
* Alias for {@link #name}.
* {@link\name}的别名。
*/
@AliasFor("name")
String value() default "";
/**
* The name of the path variable to bind to.
* @since 4.3.3
*要绑定到的路径变量的名称。
*@从4.3.3开始
*/
@AliasFor("value")
String name() default "";
/**
* Whether the path variable is required.
* Defaults to {@code true}, leading to an exception being thrown if the path
* variable is missing in the incoming request. Switch this to {@code false} if
* you prefer a {@code null} or Java 8 {@code java.util.Optional} in this case.
* e.g. on a {@code ModelAttribute} method which serves for different requests.
* @since 4.3.3
*是否需要路径变量。
*
默认为{@code true}，如果路径
*传入请求中缺少变量。如果
*您更喜欢{@codenull}或Java8{@codejava.util.可选}在这种情况下。
*例如，在为不同请求服务的{@codemodelattribute}方法上。
*@从4.3.3开始
*/
boolean required() default true;
}
@RequestBody
这个一般处理的是在ajax请求中声明contentType: “application/json; charset=utf-8”时候。也就是json数据或者xml
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestBody {
/**
* Whether body content is required.
* Default is {@code true}, leading to an exception thrown in case
* there is no body content. Switch this to {@code false} if you prefer
* {@code null} to be passed when the body content is {@code null}.
* @since 3.2
*是否需要正文内容。
*
默认值是{@code true}，这会导致在case中引发异常
*没有正文内容。如果愿意，请将其切换为{@code false}
*当正文内容为{@code null}时传递的{@code null}。
*@从3.2开始
*/
boolean required() default true;
}
@ResponseBody
将controller的方法返回的对象通过适当的转换器转换为指定的格式之后，写入到response对象的body区，通常用来返回JSON数据或者是XML数据。
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ResponseBody {
}
@RequestParam
这个一般就是在ajax里面没有声明contentType的时候，为默认的。。。urlencode格式时，用这个。
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {
/**
* Alias for {@link #name}.
*{@link\name}的别名。
*/
@AliasFor("name")
String value() default "";
/**
* The name of the request parameter to bind to.
* @since 4.2
*要绑定到的请求参数的名称。
*@从4.2开始
*/
@AliasFor("value")
String name() default "";
/**
* Whether the parameter is required.
* Defaults to {@code true}, leading to an exception being thrown
* if the parameter is missing in the request. Switch this to
* {@code false} if you prefer a {@code null} value if the parameter is
* not present in the request.
*
Alternatively, provide a {@link #defaultValue}, which implicitly
* sets this flag to {@code false}.
*是否需要参数。
*
默认为{@code true}，导致引发异常
*如果请求中缺少参数。把这个换成
*{@code false}如果参数是{@code null}值，则选择{@code false}
*请求中不存在。
*
或者，提供一个{@link#defaultValue}，它隐式地
*将此标志设置为{@code false}。
*/
boolean required() default true;
/**
* The default value to use as a fallback when the request parameter is
* not provided or has an empty value.
* Supplying a default value implicitly sets {@link #required} to
* {@code false}.
*请求参数为时用作回退的默认值
*未提供或具有空值。
*
提供默认值将{@link#required}隐式设置为
*{@code false}。
*/
String defaultValue() default ValueConstants.DEFAULT_NONE;
}
@RequestMapping
是一个用来处理请求地址映射的注解，可用于类或方法上。
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Mapping
public @interface RequestMapping {
/**
* Assign a name to this mapping.
* Supported at the type level as well as at the method level!
* When used on both levels, a combined name is derived by concatenation
* with "#" as separator.
* @see org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder
* @see org.springframework.web.servlet.handler.HandlerMethodMappingNamingStrategy
*为此映射指定一个名称。
*
在类型级别和方法级别都支持！在
*当在两个级别上使用时，组合名称是通过连接派生的
*以“#”作为分隔符。
*@看到了吗org.springframework.web.servlet.mvc.方法.annotation.MvcUriComponentsBuilder
*@看到了吗org.springframework.web.servlet.handler.HandlerMethodMappingNamingStrategy
*/
String name() default "";
/**
* The primary mapping expressed by this annotation.
* This is an alias for {@link #path}. For example,
* {@code @RequestMapping("/foo")} is equivalent to
* {@code @RequestMapping(path="/foo")}.
*
Supported at the type level as well as at the method level!
* When used at the type level, all method-level mappings inherit
* this primary mapping, narrowing it for a specific handler method.
*
NOTE: A handler method that is not mapped to any path
* explicitly is effectively mapped to an empty path.
*此批注表示的主映射。
*
这是{@link#path}的别名。例如，
*{@code@RequestMapping（“/foo”）}相当于
*{@code@RequestMapping（path=“/foo”）}。
*
在类型级别和方法级别都支持！在
*在类型级别使用时，所有方法级映射都继承
*此主映射，将其缩小为特定的处理程序方法。
*
注意：未映射到任何路径的处理程序方法
*显式地映射到空路径。
*/
@AliasFor("path")
String[] value() default {};
/**
* The path mapping URIs (e.g. {@code "/profile"}).
* Ant-style path patterns are also supported (e.g. {@code "/profile/**"}).
* At the method level, relative paths (e.g. {@code "edit"}) are supported
* within the primary mapping expressed at the type level.
* Path mapping URIs may contain placeholders (e.g. "/${profile_path}").
*
Supported at the type level as well as at the method level!
* When used at the type level, all method-level mappings inherit
* this primary mapping, narrowing it for a specific handler method.
*
NOTE: A handler method that is not mapped to any path
* explicitly is effectively mapped to an empty path.
* @since 4.2
*路径映射uri（例如{@code“/profile”}）。
*
Ant风格的路径模式也受支持（例如{@code”/profile/**“}）。
*在方法级别，支持相对路径（例如{@code“edit”}）
*在类型级别表示的主映射中。
*路径映射uri可能包含占位符（例如“/${profile\upath}”）。
*
在类型级别和方法级别都支持！在
*在类型级别使用时，所有方法级映射都继承
*此主映射，将其缩小为特定的处理程序方法。
*
注意：未映射到任何路径的处理程序方法
*显式地映射到空路径。
*@从4.2开始
*/
@AliasFor("value")
String[] path() default {};
/**
* The HTTP request methods to map to, narrowing the primary mapping:
* GET, POST, HEAD, OPTIONS, PUT, PATCH, DELETE, TRACE.
* Supported at the type level as well as at the method level!
* When used at the type level, all method-level mappings inherit
* this HTTP method restriction (i.e. the type-level restriction
* gets checked before the handler method is even resolved).
*要映射到的HTTP请求方法，缩小了主映射范围：
*GET，POST，HEAD，OPTIONS，PUT，PATCH，DELETE，跟踪。
*
在类型级别和方法级别都支持！在
*在类型级别使用时，所有方法级映射都继承
*此HTTP方法限制（即类型级别限制
*在解析处理程序方法之前进行检查）。
*/
RequestMethod[] method() default {};
/**
* The parameters of the mapped request, narrowing the primary mapping.
* Same format for any environment: a sequence of "myParam=myValue" style
* expressions, with a request only mapped if each such parameter is found
* to have the given value. Expressions can be negated by using the "!=" operator,
* as in "myParam!=myValue". "myParam" style expressions are also supported,
* with such parameters having to be present in the request (allowed to have
* any value). Finally, "!myParam" style expressions indicate that the
* specified parameter is not supposed to be present in the request.
*
Supported at the type level as well as at the method level!
* When used at the type level, all method-level mappings inherit
* this parameter restriction (i.e. the type-level restriction
* gets checked before the handler method is even resolved).
*
Parameter mappings are considered as restrictions that are enforced at
* the type level. The primary path mapping (i.e. the specified URI value)
* still has to uniquely identify the target handler, with parameter mappings
* simply expressing preconditions for invoking the handler.
*映射请求的参数，缩小主映射范围。
*
任何环境的格式相同：“myParam=myValue”样式的序列
*表达式，只有在找到每个这样的参数时才映射请求
*得到给定的值。表达式可以用“！=“操作员，
*就像“myParam！=我的值“也支持myParam“样式表达式，
*这样的参数必须出现在请求中（允许
*任何值）。最后，“！myParam”样式表达式表示
*指定的参数不应存在于请求中。
*
在类型级别和方法级别都支持！在
*在类型级别使用时，所有方法级映射都继承
*此参数限制（即类型级别限制
*在解析处理程序方法之前进行检查）。
*
参数映射被视为在
*类型级别。主路径映射（即指定的URI值）
*仍然必须使用参数映射唯一标识目标处理程序
*简单地表示调用处理程序的先决条件。
*/
String[] params() default {};
/**
* The headers of the mapped request, narrowing the primary mapping.
* Same format for any environment: a sequence of "My-Header=myValue" style
* expressions, with a request only mapped if each such header is found
* to have the given value. Expressions can be negated by using the "!=" operator,
* as in "My-Header!=myValue". "My-Header" style expressions are also supported,
* with such headers having to be present in the request (allowed to have
* any value). Finally, "!My-Header" style expressions indicate that the
* specified header is not supposed to be present in the request.
*
Also supports media type wildcards (*), for headers such as Accept
* and Content-Type. For instance,
*
* @RequestMapping(value = "/something", headers = "content-type=text/*")
*
* will match requests with a Content-Type of "text/html", "text/plain", etc.
* Supported at the type level as well as at the method level!
* When used at the type level, all method-level mappings inherit
* this header restriction (i.e. the type-level restriction
* gets checked before the handler method is even resolved).
* @see org.springframework.http.MediaType
*映射请求的头，缩小主映射范围。
*
任何环境的格式相同：“My Header=myValue”样式的序列
*表达式，只有在找到每个这样的头时才映射请求
*得到给定的值。表达式可以用“！=“操作员，
*就像“我的头！=我的值“也支持My Header“样式表达式，
*这样的头必须出现在请求中（允许
*任何值）。最后，“！“MyHeader”样式表达式表示
*指定的标头不应存在于请求中。
*
还支持媒体类型通配符（*），例如Accept
*和内容类型。例如，
*
*@；请求映射（value=“/something”，headers=“content type=text/*”）
*
*将匹配内容类型为“text/html”、“text/plain”等的请求。
*在类型级别和方法级别都支持！在
*在类型级别使用时，所有方法级映射都继承
*此标头限制（即类型级别限制
*在解析处理程序方法之前进行检查）。
*@看到了吗org.springframework.http.媒体类型
*/
String[] headers() default {};
/**
* Narrows the primary mapping by media types that can be consumed by the
* mapped handler. Consists of one or more media types one of which must
* match to the request {@code Content-Type} header. Examples:
*
* consumes = "text/plain"
* consumes = {"text/plain", "application/*"}
* consumes = MediaType.TEXT_PLAIN_VALUE
*
* Expressions can be negated by using the "!" operator, as in
* "!text/plain", which matches all requests with a {@code Content-Type}
* other than "text/plain".
* Supported at the type level as well as at the method level!
* If specified at both levels, the method level consumes condition overrides
* the type level condition.
* @see org.springframework.http.MediaType
* @see javax.servlet.http.HttpServletRequest#getContentType()
*按可由使用的媒体类型缩小主映射
*映射处理程序。由一种或多种媒体类型组成，其中一种必须
*与请求{@code Content Type}头匹配。示例：
*
*consumes=“文本/plain”
*consumes={“text/plain”，“application/*”}
*消耗=MediaType.TEXT_普通值
*
*可以使用“！”来否定表达式操作员，如
* "!text/plain”，它将所有请求与{@code Content Type}匹配
*而不是“文本/纯文本”。
*在类型级别和方法级别都支持！在
*如果在两个级别指定，则方法级别使用条件重写
*类型级别条件。
*@看到了吗org.springframework.http.媒体类型
*@看到了吗javax.servlet.http.HttpServletRequest\getContentType（）
*/
String[] consumes() default {};
/**
* Narrows the primary mapping by media types that can be produced by the
* mapped handler. Consists of one or more media types one of which must
* be chosen via content negotiation against the "acceptable" media types
* of the request. Typically those are extracted from the {@code "Accept"}
* header but may be derived from query parameters, or other. Examples:
*
* produces = "text/plain"
* produces = {"text/plain", "application/*"}
* produces = MediaType.TEXT_PLAIN_VALUE
* produces = "text/plain;charset=UTF-8"
*
* If a declared media type contains a parameter (e.g. "charset=UTF-8",
* "type=feed", type="entry") and if a compatible media type from the request
* has that parameter too, then the parameter values must match. Otherwise
* if the media type from the request does not contain the parameter, it is
* assumed the client accepts any value.
*
Expressions can be negated by using the "!" operator, as in "!text/plain",
* which matches all requests with a {@code Accept} other than "text/plain".
*
Supported at the type level as well as at the method level!
* If specified at both levels, the method level produces condition overrides
* the type level condition.
* @see org.springframework.http.MediaType
* @see org.springframework.http.MediaType
*按可由生成的媒体类型缩小主映射
*映射处理程序。由一种或多种媒体类型组成，其中一种必须
*通过内容协商与“可接受”媒体类型进行选择
*请求的。通常这些都是从{@code“Accept”}中提取的
*但可以从查询参数或其他派生。示例：
*
*products=“文本/纯文本”
*产生={“text/plain”，“application/*”}
*生产=MediaType.TEXT_普通值
*products=“text/plain；字符集=UTF-8”
*
*如果声明的媒体类型包含参数（例如“charset=UTF-8”，
*“type=feed”，type=“entry”），如果请求中有兼容的媒体类型
*也有该参数，则参数值必须匹配。否则
*如果请求中的媒体类型不包含参数，则为
*假设客户接受任何价值。
*
可以使用“！”对表达式求反操作员，如“！文本/纯文本“，
*它与除“text/plain”之外的{@code Accept}匹配所有请求。
*
在类型级别和方法级别都支持！在
*如果在两个级别指定，则方法级别将生成条件重写
*类型级别条件。
*@看到了吗org.springframework.http.媒体类型
*@看到了吗org.springframework.http.媒体类型
*/
String[] produces() default {};
}
@PostMapping
一个组合注解，是@RequestMapping(method = RequestMethod.POST)的缩写。
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping(method = RequestMethod.POST)
public @interface PostMapping {
/**
* Alias for {@link RequestMapping#name}.
* {@link RequestMapping\name}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String name() default "";
/**
* Alias for {@link RequestMapping#value}.
* {@link RequestMapping\value}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] value() default {};
/**
* Alias for {@link RequestMapping#path}.
* {@link RequestMapping\path}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] path() default {};
/**
* Alias for {@link RequestMapping#params}.
* {@link RequestMapping\params}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] params() default {};
/**
* Alias for {@link RequestMapping#headers}.
* {@link RequestMapping\headers}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] headers() default {};
/**
* Alias for {@link RequestMapping#consumes}.
* {@link RequestMapping\consumes}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] consumes() default {};
/**
* Alias for {@link RequestMapping#produces}.
* {@link RequestMapping\produces}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] produces() default {};
}
@GetMapping
一个组合注解，是@RequestMapping(method = RequestMethod.GET)的缩写。
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@RequestMapping(method = RequestMethod.POST)
public @interface GetMapping {
/**
* Alias for {@link RequestMapping#name}.
* {@link RequestMapping\name}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String name() default "";
/**
* Alias for {@link RequestMapping#value}.
* {@link RequestMapping\value}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] value() default {};
/**
* Alias for {@link RequestMapping#path}.
* {@link RequestMapping\path}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] path() default {};
/**
* Alias for {@link RequestMapping#params}.
* {@link RequestMapping\params}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] params() default {};
/**
* Alias for {@link RequestMapping#headers}.
* {@link RequestMapping\headers}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] headers() default {};
/**
* Alias for {@link RequestMapping#consumes}.
* {@link RequestMapping\consumes}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] consumes() default {};
/**
* Alias for {@link RequestMapping#produces}.
* {@link RequestMapping\produces}的别名。
*/
@AliasFor(annotation = RequestMapping.class)
String[] produces() default {};
}
@target
通常用在生命自定义一个新的注解时使用，用来定义这个自定义的注解可以作用在什么上面，比如类、接口、注解、枚举， 字段， 普通方法， 参数， 构造方法， 局部变量， 注解， 包
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.ANNOTATION_TYPE)
public @interface Target {
/**
* Returns an array of the kinds of elements an annotation type
* can be applied to.
* @return an array of the kinds of elements an annotation type
* can be applied to
*返回批注类型的元素类型的数组
*可以应用于。
*@返回注释类型元素的数组
*可应用于
*/
ElementType[] value();
}
@Retention
Reteniton的作用是定义被它所注解的注解保留多久，一共有三种策略，定义在RetentionPolicy枚举中
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.ANNOTATION_TYPE)
public @interface Retention {
/**
* Returns the retention policy.
* @return the retention policy
*返回保留策略。
*@返回保留策略
*/
RetentionPolicy value();
}
public enum RetentionPolicy {
/**
* Annotations are to be discarded by the compiler.
* 注释将被编译器丢弃。
*/
SOURCE,
/**
* Annotations are to be recorded in the class file by the compiler
* but need not be retained by the VM at run time. This is the default
* behavior.
*注释将由编译器记录在类文件中
*但不需要在运行时被VM保留。这是默认值
*行为。
*/
CLASS,
/**
* Annotations are to be recorded in the class file by the compiler and
* retained by the VM at run time, so they may be read reflectively.
*
* @see java.lang.reflect.AnnotatedElement
*注释将由编译器记录在类文件中，并且
*在运行时被VM保留，因此可以反射性地读取它们。
*
*@看到了吗java.lang.reflect.注释删除
*/
RUNTIME
}
@Inherited
使用此注解声明出来的自定义注解，在使用此自定义注解时，如果注解在类上面时，子类会自动继承此注解，否则的话，子类不会继承此注解。这里一定要记住，使用Inherited声明出来的注解，只有在类上使用时才会有效，对方法，属性等其他无效。
/**
* Indicates that an annotation type is automatically inherited. If
* an Inherited meta-annotation is present on an annotation type
* declaration, and the user queries the annotation type on a class
* declaration, and the class declaration has no annotation for this type,
* then the class's superclass will automatically be queried for the
* annotation type. This process will be repeated until an annotation for this
* type is found, or the top of the class hierarchy (Object)
* is reached. If no superclass has an annotation for this type, then
* the query will indicate that the class in question has no such annotation.
*
* Note that this meta-annotation type has no effect if the annotated
* type is used to annotate anything other than a class. Note also
* that this meta-annotation only causes annotations to be inherited
* from superclasses; annotations on implemented interfaces have no
* effect.
*指示自动继承批注类型。如果
*批注类型上存在继承的元批注
*声明，并且用户查询类上的注释类型
*声明，而类声明没有此类型的注释，
*然后类的超类将自动查询
*批注类型。此过程将重复，直到对此进行注释
*找到类型，或类层次结构（对象）的顶部
*已到达。如果没有超类具有此类型的注释，则
*查询将指示相关类没有此类注释。
*
*
请注意，如果
*类型用于注释类以外的任何内容。也请注意
*这个元注释只会导致注释被继承
*从超类；实现接口上的注释没有
*效果。
*
* @author Joshua Bloch
* @since 1.5
* @jls 9.6.3.3 @Inherited
*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.ANNOTATION_TYPE)
public @interface Inherited {
}
@Profile
注解在方法类上在不同情况下选择实例化不同的Bean特定环境下生效！
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(ProfileCondition.class)
public @interface Profile {
/**
* The set of profiles for which the annotated component should be registered.
*应为其注册带注释组件的配置文件集。
*/
String[] value();
}
@SuppressWarnings
抑制警告
@Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE})
@Retention(RetentionPolicy.SOURCE)
public @interface SuppressWarnings {
/**
* The set of warnings that are to be suppressed by the compiler in the
* annotated element. Duplicate names are permitted. The second and
* successive occurrences of a name are ignored. The presence of
* unrecognized warning names is not an error: Compilers must
* ignore any warning names they do not recognize. They are, however,
* free to emit a warning if an annotation contains an unrecognized
* warning name.
*
* The string {@code "unchecked"} is used to suppress
* unchecked warnings. Compiler vendors should document the
* additional warning names they support in conjunction with this
* annotation type. They are encouraged to cooperate to ensure
* that the same names work across multiple compilers.
* @return the set of warnings to be suppressed
*中编译器要禁止的警告集
*带注释的元素。允许重复名称。第二个和
*将忽略连续出现的名称。存在
*无法识别的警告名称是不是错误：编译器必须
*忽略他们无法识别的任何警告名称。但是，他们是，
*如果批注包含无法识别的
*警告名称。
*
*
字符串{@code“unchecked”}用于抑制
*未经检查的警告。编译器供应商应记录
*它们支持与此相关的其他警告名称
*批注类型。鼓励他们合作以确保
*在多个编译器中使用相同的名称。
*@返回要抑制的警告集
*/
String[] value();
}
@Modifying
如果是增，改，删加上此注解
- 方法的返回值应该是int，表示更新语句所影响的行数。
- 在调用的地方必须加事务，没有事务不能正常执行。@Transactional 事务注解