Spring笔记(1) - 组件注册及部分源码解析

1. @Bean：类注入容器

   1. xml方式：

      class="com.hrh.bean.Person">
          
          
      
      public static void main(String[] args) {
          ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
          Person person = (Person) context.getBean("person");
          System.out.println(person);
      }

   2. @Bean+@Configuration方式：

      @Configuration//配置类==配置文件
      public class BeanConfig {
          @Bean
          public Person person(){
              return new Person("张三",20);
          }
      }
      AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BeanConfig.class);
      Person person = (Person)context.getBean("person"); 

2. @ComponentScan：扫描类注入容器

   1. xml方式：

      
          <context:component-scan base-package="com.hrh" use-default-filters="false"/>

   2. @ComponentScan方式：JDK1.8的ComponentScan是Repeatable的，即可以在类上定义多个@ComponentScan

      @Configuration//配置类==配置文件
      /**
       * value：指定要扫描的包
       * includeFilters：指定扫描时只需要包含哪些组件，需要使用useDefaultFilters = false使规则生效
       * excludeFilters：指定扫描时按照什么规则排除哪些组件
       */
      @ComponentScan(value = "com.hrh",includeFilters = {
              @Filter(type = FilterType.ANNOTATION,
              classes = {Controller.class})
      },useDefaultFilters = false)
      public class BeanConfig {
          @Bean
          public Person person(){
              return new Person("张三",20);
          }
      }
      //====结果====
      org.springframework.context.annotation.internalConfigurationAnnotationProcessor
      org.springframework.context.annotation.internalAutowiredAnnotationProcessor
      org.springframework.context.annotation.internalCommonAnnotationProcessor
      org.springframework.context.event.internalEventListenerProcessor
      org.springframework.context.event.internalEventListenerFactory
      beanConfig
      userController
      person

   3. @ComponentScans：如果不是JDK1.8，可以使用该注解定义多个@ComponentScan

      @ComponentScans({
              @ComponentScan(value = "com.hrh",includeFilters = {
                      @ComponentScan.Filter(type = FilterType.ANNOTATION,
                              classes = {Controller.class})
              },useDefaultFilters = false)
      })
      public class BeanConfig {
          @Bean
          public Person person(){
              return new Person("张三",20);
          }
      }

   4. @Filter：过滤规则

      @Configuration//配置类==配置文件
      /**
       * FilterType.ANNOTATION：根据注解扫描指定的类
       * FilterType.ASSIGNABLE_TYPE：按照给定的类型,如果是接口类型，其实现类和子类注入容器；如果是类，本类和子类注入容器
       * FilterType.ASPECTJ：使用ASPECTJ表达式
       * FilterType.REGEX：使用正则表达式
       * FilterType.CUSTOM：使用自定义规则,自定义实现TypeFilter接口，重写match方法
       */
      @ComponentScan(value = "com.hrh", includeFilters = {
      //        @ComponentScan.Filter(type = FilterType.ANNOTATION,
      //                classes = {IUserService.class}),
      //        @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE,
      //        classes = {IUserService.class}),
              @ComponentScan.Filter(type = FilterType.CUSTOM,classes ={MyTypeFilter.class} )
      }, useDefaultFilters = false)
      public class BeanConfig {
          @Bean
          public Person person() {
              return new Person("张三", 20);
          }
      }
      
      public class MyTypeFilter implements TypeFilter {
          /**
           *
           * @param metadataReader 读取到的当前正在扫描的类的信息
           * @param metadataReaderFactory 可以获取到其他任何类的信息
           * @return ture则将类加入容器
           * @throws IOException
           */
          public boolean match(MetadataReader metadataReader, MetadataReaderFactory metadataReaderFactory) throws IOException {
              //获取当前类注解的信息
              AnnotationMetadata annotationMetadata = metadataReader.getAnnotationMetadata();
              //获取当前类资源（类路径）
              Resource resource = metadataReader.getResource();
              //获取当前正在扫描的类的类信息
              ClassMetadata classMetadata = metadataReader.getClassMetadata();
              String className = classMetadata.getClassName();
              System.out.println("className:"+className);
              if(className.contains("Controller")){
                  return true;
              }
              return false;
          }
      }
      //====结果====
      className:com.hrh.bean.Person
      className:com.hrh.config.MyTypeFilter
      className:com.hrh.controller.UserController
      className:com.hrh.dao.UserDao
      className:com.hrh.service.IUserService
      className:com.hrh.service.SubUserService
      className:com.hrh.service.UserService
      org.springframework.context.annotation.internalConfigurationAnnotationProcessor
      org.springframework.context.annotation.internalAutowiredAnnotationProcessor
      org.springframework.context.annotation.internalCommonAnnotationProcessor
      org.springframework.context.event.internalEventListenerProcessor
      org.springframework.context.event.internalEventListenerFactory
      beanConfig
      userController
      person

3. @Scope：作用域

   @Configuration
   @ComponentScan(value = "com.hrh")
   public class BeanConfig {
       /**
        * ConfigurableBeanFactory#SCOPE_PROTOTYPE：prototype
        * ConfigurableBeanFactory#SCOPE_SINGLETON：singleton
        * org.springframework.web.context.WebApplicationContext#SCOPE_REQUEST：request
        * org.springframework.web.context.WebApplicationContext#SCOPE_SESSION：session
        * prototype：多实例(原型)，只有在获取的时候才会注入容器，每次获取都会进行创建对象注入不同的实例，每次获取的对象都不同
        * singleton：单实例(默认值)，ioc容器启动会调用该方法创建对象注入容器，每次获取直接中容器中拿
        * request：同一次请求创建一个实例
        * session：同一个session创建一个实例
        */
   
       @Scope(value = "prototype")
       @Bean
       public Person person() {
           System.out.println("注入容器。。。。。");
           return new Person("张三", 20);
       }

   • @Lazy：懒加载，项目启动时不创建对象注入容器，只在第一次调用时才创建对象并初始化

         @Lazy
         @Bean
         public Person person() {
             System.out.println("注入容器。。。。。");
             return new Person("张三", 20);
         }

4. @Conditional：按照条件注入容器，实现Condition的matches()

   @Configuration
   @ComponentScan(value = "com.hrh")
   public class BeanConfig {
       @Conditional(WindowsConfig.class)
       @Bean(value = "Bill")
       public Person person1() {
           System.out.println("创建Windows。。。。。");
           return new Person("Bill", 20);
       }
       @Conditional(LinuxConfig.class)
       @Bean(value = "Linux")
       public Person person2() {
           System.out.println("创建Linux。。。。。");
           return new Person("Linux", 20);
       }
   }
   public class WindowsConfig implements Condition {
       /**
        *
        * @param context 判断条件能使用的上下文
        * @param metadata 注释信息
        * @return
        */
       public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
           //获取ioc使用的beanFactory
           ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
           //获取类加载器
           ClassLoader classLoader = beanFactory.getBeanClassLoader();
           Environment environment = context.getEnvironment();
           String property = environment.getProperty("os.name");
           if("Windows 10".equals(property)){
               return true;//当前系统环境是windows 10，将条件下的bean注入容器
           }
           return false;
       }
   }
   public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
           //获取ioc使用的beanFactory
           ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
           //获取类加载器
           ClassLoader classLoader = beanFactory.getBeanClassLoader();
           Environment environment = context.getEnvironment();
           String property = environment.getProperty("os.name");
           if("Linux".equals(property)){
               return true;
           }
           return false;
       }

5.  @Import：快速导入组件进容器

   public class Color {
   }
   @Configuration
   @ComponentScan(value = "com.hrh")
   @Import(Color.class)
   //@Import({Color.class,Person.class})导入多个
   public class BeanConfig {}
   public static void main(String[] args) {
       AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BeanConfig.class);
       String[] beanDefinitionNames = context.getBeanDefinitionNames();
       for(String beanName:beanDefinitionNames){
           System.out.println(beanName);
       }
   }

   1. ImportSelector：实现该接口，重写selectImports()

      public class MyImportSelector implements ImportSelector {
          /**
           *
           * @param importingClassMetadata 当前标注@Import的类的全部注解信息，比如该类还标注了@Configuration也会被获取到
           * @return 返回的组件全类名加入到容器中
           */
          public String[] selectImports(AnnotationMetadata importingClassMetadata) {
              return new String[]{"com.hrh.bean.Color","com.hrh.bean.Person"};
          }
      }
      
      @Configuration
      @ComponentScan(value = "com.hrh")
      @Import({MyImportSelector.class})
      public class BeanConfig {}

   2. ImportBeanDefinitionRegistrar：实现ImportBeanDefinitionRegistrar，重写registerBeanDefinitions()

      @Configuration
      @Import({Color.class,MyImportBeanDefinitionRegistrar.class})
      public class BeanConfig {}
      public class MyImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {
          /**
           *
           * @param importingClassMetadata 当前类的注解信息
           * @param registry BeanDefinition注册类，把所有需要添加到容器中的bean，调用BeanDefinitionRegistryregisterBeanDefinition注册进来
           */
          @Override
          public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
              boolean color = registry.containsBeanDefinition("com.hrh.bean.Color");
              //容器中有Color类才将Person类进行注入
              if(color) {
                  RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(Person.class);
                  registry.registerBeanDefinition("person",rootBeanDefinition);
              }
      
          }
      } 

6. FactoryBean

   public class MyFactoryBean implements FactoryBean {
       //返回一个对象，并且该对象会注入容器
       @Override
       public Color getObject() throws Exception {
   
           return new Color();
       }
   
       @Override
       public Class getObjectType() {
           return Color.class;
       }
   
       @Override
       public boolean isSingleton() {
           return true;
       }
   }
   @Configuration
   public class BeanConfig {
       /**
        * 1.默认获取的是MyFactoryBean调用getObject创建的对象
        * 2.要获取MyFactoryBean本身，需要给id前加&，比如&myBeanFactory
        */
       @Bean
       public MyFactoryBean myBeanFactory(){
           return new MyFactoryBean();
       }
   }
   AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(BeanConfig.class);
   Object bean1=context.getBean("myBeanFactory");
   System.out.println(bean1.getClass());
   Object bean2=context.getBean("&myBeanFactory");
   System.out.println(bean2.getClass());