Java从入门到入土之Spring-IoC篇

1.Spring是什么
  Spring是一个开源框架，Spring是于2003 年兴起的一个轻量级的Java 开发框架，由Rod Johnson 在其著作Expert One-On-One J2EE Development and Design中阐述的部分理念和原型衍生而来。它是为了解决企业应用开发的复杂性而创建的。框架的主要优势之一就是其分层架构，分层架构允许使用者选择使用哪一个组件，同时为 J2EE 应用程序开发提供集成的框架。Spring使用基本的JavaBean来完成以前只可能由EJB完成的事情。然而，Spring的用途不仅限于服务器端的开发。从简单性、可测试性和松耦合的角度而言，任何Java应用都可以从Spring中受益。Spring的核心是控制反转（IoC）和面向切面（AOP）。
2.Spring的优点
　　①、方便解耦，简化开发
　　通过Spring提供的IoC容器，我们可以将对象之间的依赖关系交由Spring进行控制，避免硬编码所造成的过度程序耦合。有了Spring，用户不必再为单实例模式类、属性文件解析等这些很底层的需求编写代码，可以更专注于上层的应用。
　　
　　②、AOP编程的支持
　　通过Spring提供的AOP功能，方便进行面向切面的编程，许多不容易用传统OOP实现的功能可以通过AOP轻松应付。
　　
　　③、声明式事务的支持
　　在Spring中，我们可以从单调烦闷的事务管理代码中解脱出来，通过声明式方式灵活地进行事务的管理，提高开发效率和质量。
　　
　　④、方便程序的测试
　　可以用非容器依赖的编程方式进行几乎所有的测试工作，在Spring里，测试不再是昂贵的操作，而是随手可做的事情。例如：Spring对Junit4支持，可以通过注解方便的测试Spring程序。
　　
　　⑤、方便集成各种优秀框架
　　Spring不排斥各种优秀的开源框架，相反，Spring可以降低各种框架的使用难度，Spring提供了对各种优秀框架（如Struts,Hibernate、Hessian、Quartz）等的直接支持。

⑥、降低Java EE API的使用难度
　　Spring对很多难用的Java EE API（如JDBC，JavaMail，远程调用等）提供了一个薄薄的封装层，通过Spring的简易封装，这些Java EE API的使用难度大为降低。

⑦、Java 源码是经典学习范例
　　Spring的源码设计精妙、结构清晰、匠心独运，处处体现着大师对Java设计模式灵活运用以及对Java技术的高深造诣。Spring框架源码无疑是Java技术的最佳实践范例。如果想在短时间内迅速提高自己的Java技术水平和应用开发水平，学习和研究Spring源码将会使你收到意想不到的效果。
3.Spring需要的jar包

4.spring配置文件
pojo实体类

package com.pojo;

public class Student {

	private int sid;
	private String name;
	public Student() {
		super();
	}
	public Student(int sid, String name) {
		super();
		this.sid = sid;
		this.name = name;
	}
	public int getSid() {
		return sid;
	}
	public void setSid(int sid) {
		this.sid = sid;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "Student{" +
				"sid=" + sid +
				", name='" + name + '\'' +
				'}';
	}
}

IOC（控制反转）
构造函数创建Bean
配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    
    <bean id="student1" class="com.pojo.Student">
        
        <property name="name" value="张三"/>
        <property name="sid" value="1"/>
    bean>
   
    <bean id="student2" class="com.pojo.Student" scope="singleton">
        <constructor-arg index="0" value="1">constructor-arg>
        <constructor-arg index="1" value="jack">constructor-arg>
    bean>
beans>

测试类

public class Test1 {

    public static void main(String[] args) {
        /*创建spring容器对象*/
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        /*通过spring容器获取student对象*/
        Student student1 = (Student) ac.getBean("student1");
        System.out.println(student1);
        Student student2 = (Student) ac.getBean("student2");
        System.out.println(student2);

    }
}

运行结果

七月 25, 2019 9:30:10 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 09:30:10 CST 2019]; root of context hierarchy
七月 25, 2019 9:30:10 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
Student{sid=1, name='张三'}
Student{sid=1, name='jack'}

静态工厂方法创建Bean
静态工厂类

public class StaticStudentFactory {

    private static Student student;

    public static Student getStudent(int sid,String name) {
        student = new Student(sid,name);
        return student;
    }

}

配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    
    <bean id="student3" class="com.factory.StaticStudentFactory" factory-method="getStudent">
        
        <constructor-arg index="0" value="1"/>
        <constructor-arg index="1" value="Tom"/>
    bean>
beans>

测试类

public class Test1 {

    public static void main(String[] args) {
        /*创建spring容器对象*/
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        /*通过spring容器获取student对象*/
        Student student3 = (Student) ac.getBean("student3");
        System.out.println(student3);
    }
}

运行结果

七月 25, 2019 9:34:47 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 09:34:47 CST 2019]; root of context hierarchy
七月 25, 2019 9:34:48 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
Student{sid=1, name='Tom'}

Process finished with exit code 0

实例化工厂
实例化工厂类

public class InstanceStudentFactory {

    private Student student;

    public Student getStudent(int sid,String name){
        student =  new Student(sid,name);
        return student;
    }
}

配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    
    
    <bean id="StudentFactory" class="com.factory.InstanceStudentFactory">
    bean>
    
    <bean id="student4" factory-bean="StudentFactory" factory-method="getStudent">
        
        <constructor-arg index="0" value="1"/>
        <constructor-arg index="1" value="roes"/>
    bean>
beans>

测试类

public class Test1 {

    public static void main(String[] args) {
        /*创建spring容器对象*/
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        /*通过spring容器获取student对象*/
        Student student4 = (Student) ac.getBean("student4");
        System.out.println(student4);
    }
}

运行结果

七月 25, 2019 9:44:53 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 09:44:53 CST 2019]; root of context hierarchy
七月 25, 2019 9:44:53 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
Student{sid=1, name='roes'}

Process finished with exit code 0

使用注解
配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
   http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
   http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">
  	 
    <context:component-scan base-package="com.pojo">context:component-scan>
beans>

需要导入context的xsd

package com.pojo;

import org.springframework.stereotype.Component;

/*value 获取Bean的id
* 可以省略直接写@Component 则id为类名首字母小写*/
@Component(value = "abc")
public class Student {

	private int sid;
	private String name;
	public Student() {
		super();
	}
	public Student(int sid, String name) {
		super();
		this.sid = sid;
		this.name = name;
	}
	public int getSid() {
		return sid;
	}
	public void setSid(int sid) {
		this.sid = sid;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}

	@Override
	public String toString() {
		return "Student{" +
				"sid=" + sid +
				", name='" + name + '\'' +
				'}';
	}
}

只需要在类的上面加上@Component注解。value 获取Bean的id 可以省略直接写@Component 则id为类名首字母小写
DI（依赖注入）
pojo实体类
Dog类只有一个String name的属性

package com.pojo;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class People {
    private int id;

    private String name;

    private List<String> list;

    private Set<String> set;

    private Map<String,String> map;

    private Properties prop;

    private Dog dog;

    public People(int id, String name, List<String> list, Set<String> set, Map<String, String> map, Properties prop, Dog dog) {
        this.id = id;
        this.name = name;
        this.list = list;
        this.set = set;
        this.map = map;
        this.prop = prop;
        this.dog = dog;
    }

    public People() {
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<String> getList() {
        return list;
    }

    public void setList(List<String> list) {
        this.list = list;
    }

    public Set<String> getSet() {
        return set;
    }

    public void setSet(Set<String> set) {
        this.set = set;
    }

    public Map<String, String> getMap() {
        return map;
    }

    public void setMap(Map<String, String> map) {
        this.map = map;
    }

    public Properties getProp() {
        return prop;
    }

    public void setProp(Properties prop) {
        this.prop = prop;
    }

    public Dog getDog() {
        return dog;
    }

    public void setDog(Dog dog) {
        this.dog = dog;
    }

    @Override
    public String toString() {
        return "People{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", list=" + list +
                ", set=" + set +
                ", map=" + map +
                ", prop=" + prop +
                ", dog=" + dog +
                '}';
    }
}

通过Set方法注入属性
配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
     http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd">
    
    <bean id="lq" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="locations">
            <list>
                <value>classpath*:lq.propertiesvalue>
            list>
        property>
    bean>
    
    <bean id="dog" class="com.pojo.Dog">
        <property name="name" value="来福"/>
    bean>
    
    <bean id="people" class="com.pojo.People">
        
        <property name="id" value="1">property>
        <property name="name" value="李青 ">property>
        
        <property name="list">
            <list>
                <value>打野value>
                <value>上单value>
                <value>辅助value>
                <value>中单value>
            list>
        property>
        
        <property name="set">
            <set>
                <value>aaavalue>
                <value>bbbvalue>
                <value>cccvalue>
                <value>aaavalue>
            set>
        property>
        
        <property name="map">
            <map >
                <entry key="装备1" value="无尽之刃">entry>
                <entry key="装备2" value="饮血剑">entry>
                <entry key="装备3" value="绿叉">entry>
                <entry key="装备4" value="羊刀">entry>
            map>
        property>
        
        <property name="prop" ref="lq">property>
        
        <property name="dog" ref="dog">property>
    bean>
beans>

外部文件lq.propert

k1=aaa
k2=bbb
k3=ccc
k4=ddd

测试类

package com.test;

import com.pojo.People;
import com.pojo.Student;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test1 {

    public static void main(String[] args) {
        /*创建spring容器对象*/
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        /*通过spring容器获取student对象*/
        People people = (People) ac.getBean("people");
        System.out.println(people);
    }
}

运行结果

七月 25, 2019 11:12:03 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 11:12:03 CST 2019]; root of context hierarchy
七月 25, 2019 11:12:03 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
七月 25, 2019 11:12:03 上午 org.springframework.beans.factory.config.PropertiesFactoryBean loadProperties
信息: Loading properties file from URL [file:/C:/Users/lx/Desktop/01spring/out/production/01spring/lq.properties]
People{id=1, name='李青 ', list=[打野, 上单, 辅助, 中单], set=[aaa, bbb, ccc], map={装备1=无尽之刃, 装备2=饮血剑, 装备3=绿叉, 装备4=羊刀}, prop={k4=ddd, k3=ccc, k2=bbb, k1=aaa}, dog=Dog{name='来福'}}

Process finished with exit code 0

构造器注入属性

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
     http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd">
    
    <bean id="lq" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
        <property name="locations">
            <list>
                <value>classpath*:lq.propertiesvalue>
            list>
        property>
    bean>
    
    <bean id="dog" class="com.pojo.Dog">
        <property name="name" value="来福"/>
    bean>
    
    <bean id="people" class="com.pojo.People">
        
        <constructor-arg index="0" value="1"/>
        <constructor-arg index="1" value="李青"/>
        
        <constructor-arg index="2" type="java.util.List">
            <list>
                <value>打野value>
                <value>上单value>
                <value>辅助value>
                <value>中单value>
            list>
        constructor-arg>
        <constructor-arg index="3" type="java.util.Set">
            <set>
                <value>aaavalue>
                <value>bbbvalue>
                <value>cccvalue>
                <value>aaavalue>
            set>
        constructor-arg>
        <constructor-arg index="4" type="java.util.Map">
            <map >
                <entry key="装备1" value="无尽之刃">entry>
                <entry key="装备2" value="饮血剑">entry>
                <entry key="装备3" value="绿叉">entry>
                <entry key="装备4" value="羊刀">entry>
            map>
        constructor-arg>
        
        <constructor-arg index="5" type="java.util.Properties" ref="lq">
        constructor-arg>
        <constructor-arg type="com.pojo.Dog" ref="dog">constructor-arg>
    bean>
beans>

运行结果

七月 25, 2019 11:19:56 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 11:19:56 CST 2019]; root of context hierarchy
七月 25, 2019 11:19:56 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
七月 25, 2019 11:19:57 上午 org.springframework.beans.factory.config.PropertiesFactoryBean loadProperties
信息: Loading properties file from URL [file:/C:/Users/lx/Desktop/01spring/out/production/01spring/lq.properties]
People{id=1, name='李青', list=[打野, 上单, 辅助, 中单], set=[aaa, bbb, ccc], map={装备1=无尽之刃, 装备2=饮血剑, 装备3=绿叉, 装备4=羊刀}, prop={k4=ddd, k3=ccc, k2=bbb, k1=aaa}, dog=Dog{name='来福'}}

Process finished with exit code 0

通过注解实现注入
配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
   http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd"
    default-autowire="byName">
    
    
    <context:component-scan base-package="com.pojo"/>
beans>

pojo实体类

package com.pojo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;

@Component
public class Demo {
    /*@Autowired是根据类型自动装配的,加上@Qualifier则可根据byName的方式自动装配，其中@Qualifier不能单独使用。
     *@Qualifier(value = "student") 括号中的value属性必须有不然会报错
     *@Resource如有指定的name属性，先按该属性进行byName方式查找装配；其次再进行默认的byName方式进行装配；        以上都不成功，则按byType的方式自动装配。@Resource(name="student")括号中可不写。
     *@Autowired，@Qualifier是spring提供的注解 @Resource是Java提供的注解 */
    @Autowired
    @Qualifier(value = "student")
    @Resource(name="student")
    private Student student;

    public Student getStudent() {
        return student;
    }

    public void setStudent(Student student) {
        this.student = student;
    }

    @Override
    public String toString() {
        return "Demo{" +
                "student=" + student +
                '}';
    }
}

运行结果

七月 25, 2019 11:47:56 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@31221be2: startup date [Thu Jul 25 11:47:56 CST 2019]; root of context hierarchy
七月 25, 2019 11:47:56 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
Demo{student=Student{sid=0, name='null'}}

Process finished with exit code 0

student被初始化，没有初始化属性。