原文:

基于XML的配置，Bean定义信息和Bean实现类本身是分离的，而采用基于注解的配置方式时，Bean定义信息即通过在Bean实现类上标注注解实现。

@Component：对类进行标注，Spring容器自动将POJO转换为容器管理的Bean；

@Repository：用于对DAO实现类进行标注；

@Service：用于对Service实现类进行标注；

@Controller：用于对Controller实现类进行标注。

 

1、自动装配Bean：

 

beans.xml：

 LogDao类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;@Component("logDao")public class LogDao {}

UserDao_1类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;@Component("userDao_1")//自动被Spring容器识别，Spring容器自动将POJO转换为容器管理的Bean//等价于XML配置的
      
       public class UserDao_1 {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "UserDao_1{" +                "name='" + name + '\t' +                '}';    }    public UserDao_1() {        System.out.println("userDao");    }}
      

UserDao_2类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;/** * Created by gao on 16-3-25. */@Component("userDao_2")public class UserDao_2 {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "UserDao_2{" +                "name='" + name + '\t' +                '}';    }    public UserDao_2() {        System.out.println("userDao_2");    }}

UserDao_3类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;/** * Created by gao on 16-3-25. */@Component("userDao_3")public class UserDao_3 {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "UserDao_3{" +                "name='" + name + '\t' +                '}';    }    public UserDao_3() {        System.out.println("userDao_3");    }}

LogonService类：

package com.ioc.ch4_10;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.stereotype.Service;@Servicepublic class LogonService{    //使用@Autowired进行自动注入    @Autowired    private LogDao logDao;    @Autowired    private UserDao_1 userDao1;    //使用@Autowired的required属性，设置为false表示找不到匹配的Bean完成注入也不要抛出异常    @Autowired(required = false)    private UserDao_2 userDao_2;    //使用@Qualifier指定注入Bean的名称    @Autowired    @Qualifier("userDao_3")    private UserDao_3 userDao_3;    public LogDao getLogDao() {        return logDao;    }    public UserDao_1 getUserDao1() {        return userDao1;    }    public UserDao_2 getUserDao2() {        return userDao_2;    }    public UserDao_3 getUserDao3() {        return userDao_3;    }    public void printSomething(){        userDao1.setName("LogonService-userDao1");        System.out.println(userDao1.toString());        userDao_2.setName("LogonService-userDao2");        System.out.println(userDao_2.toString());        userDao_3.setName("LogonService-userDao3");        System.out.println(userDao_3.toString());    }}

LoginService_2类：

package com.ioc.ch4_10;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.stereotype.Service;/** * Created by gao on 16-3-25. */@Servicepublic class LogonService_2 {    private LogDao logDao;    private UserDao_1 userDao_1;    //自动将LogDao传给方法入参    @Autowired    public void setLogDao(LogDao logDao) {        System.out.println("auto setlogdao");        this.logDao = logDao;    }    //自动将名为userDao的Bean传给方法入参    @Autowired    public void setUserDao_1(UserDao_1 userDao_1) {        System.out.println("auto setuserdao");        this.userDao_1 = userDao_1;    }    @Autowired    public void init(@Qualifier("userDao_1")UserDao_1 userDao,LogDao logDao){        System.out.println("multi param inject");        this.userDao_1 = userDao;        this.logDao =logDao;    }}

测试类：

package com.ioc.ch4_10;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** * Created by gao on 16-3-25. */public class Test {    public static void main(String[] args) {        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:com\\ioc\\ch4_10\\beans.xml");        LogonService ls = (LogonService) ctx.getBean("ls");        ls.printSomething();    }}

 

输出结果：

userDao

userDao_2

userDao_3

multi param inject

auto setlogdao

auto setuserdao

UserDao_1{name='LogonService??userDao1}

UserDao_2{name='LogonService-userDao2

}

UserDao_3{name='LogonService-userDao3

}

 

 

2、对集合类进行标注

Plugin接口：

package com.ioc.ch4_10;public interface Plugin {}

 onePlugin类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;@Componentpublic class OnePlugin implements Plugin {}

twoPlugin类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;@Componentpublic class TwoPlugin implements Plugin {}

MyComponent类：

package com.ioc.ch4_10;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import java.util.List;@Componentpublic class MyComponent {    //Spring会将容器中所有类型为Plugin的Bean注入到这个变量中    @Autowired(required=false)    private List
       
         plugins;    public List
        
          getPlugins() {        return plugins;    }}
        
       

mycomponent.xml：

MyComponentTest类：

package com.ioc.ch4_10;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class MyComponentTest {    public static void main(String[] args) throws Throwable {        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:com\\ioc\\ch4_10\\mycomponent.xml");        MyComponent myComponent = ctx.getBean(MyComponent.class);        System.out.println("pulgin.size:"+myComponent.getPlugins().size());            }}

输出结果：

userDao

userDao_2

userDao_3

multi param inject

auto setlogdao

auto setuserdao

pulgin.size:2

 

3、Bean作用范围及生命过程方法

使用Scope指定作用范围

package com.ioc.ch4_10;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.context.annotation.Scope;import org.springframework.stereotype.Component;//指定Bean的作用范围为prototype@Scope(BeanDefinition.SCOPE_PROTOTYPE)@Componentpublic class Car {    private int maxSpeed;    public String brand;    private double price;        ......}

 

 Boss类：

package com.ioc.ch4_10;import org.springframework.stereotype.Component;import javax.annotation.PostConstruct;import javax.annotation.PreDestroy;import javax.annotation.Resource;@Componentpublic class Boss {        private Car car;    public Boss(){        System.out.println("construct...");    }    @Resource    private void setCar(Car car){        System.out.println("execute in setCar");        this.car = car;    }        @PostConstruct    private void init1(){        System.out.println("execute in init1");    }        @PostConstruct    private void init2(){        System.out.println("execute in init1");    }        @PreDestroy    private void destory1(){        System.out.println("execute in destory1");    }        @PreDestroy    private void destory2(){        System.out.println("execute in destory2");    }}

测试类：

package com.ioc.ch4_10;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** * Created by gao on 16-3-25. */public class Test {    public static void main(String[] args) {        ApplicationContext ctx = new ClassPathXmlApplicationContext("classpath:com\\ioc\\ch4_10\\beans.xml");        Car car1 = (Car) ctx.getBean("car");        Car car2 = (Car) ctx.getBean("car");        System.out.println(car1 == car2); //false        UserDao_2 ud1 = (UserDao_2) ctx.getBean("userDao_2");        UserDao_2 ud2 = (UserDao_2) ctx.getBean("userDao_2");        System.out.println(ud1 == ud2); //true        ((ClassPathXmlApplicationContext)ctx).destroy();    }}

输出结果：

construct...

execute in setCar

execute in init1

execute in init1

false

true

execute in destory2

execute in destory1