Bean的属性注入

Bean 的属性注入有两种方式

①构造器注入

②setter注入(重点)

一、构造器注入

 Spring使用构造器注入Bean属性 提供对应参数的构造器 为Bean配置使用构造器注入

/**
    *实体类
    */
 
public class User {
    private String name;
    private int age;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public User(){
        System.out.println("User.User()无参构造");
    }
    public User(String name,int age){
        System.out.println("User.User()有参构造");
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
    
}

<!-- XML配置文件-->
<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
    <bean id="user" class="com.wd.bean.User">
        <constructor-arg index="0" value="张三"></constructor-arg>
        <constructor-arg index="1" value="12"></constructor-arg>
    </bean>        

</beans>

/**
 * 测试类
 * @author Thinkpad
 *
 */
public class Test {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        User user =  (User) ac.getBean("user");
        System.out.println(user);
    }
}

结果：

二、setter注入Bean属性(重点)

① Spring使用属性对应的setter方法为属性注入资源 为属性提供对应的setter方法

//实体类如上

<!--XML配置文件-->

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
    <bean id="user" class="com.wd.bean.User">
        <property name="name" value="李四"/>
        <property name="age" value="55"/>
    </bean>        

</beans>

/**
 * 测试类
 * @author Thinkpad
 *
 */
public class Test {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        User user =  (User) ac.getBean("user");
        System.out.println(user);
    }
}

输出结果：

 

②Spring注入引用类型的对象，必须保障该对象以 Bean形式存在于IoC容器，受Spring控制 为属性提供对应的setter方法

//dao接口
public interface DaoI {
    public void add();
    public void del();
    public void update();
}

//dao接口实现类

public class MyDaoTest implements DaoI {

    @Override
    public void add() {
        System.out.println("MyDaoTest.add()MyDaoTest dao被调用了");
    }

    @Override
    public void del() {
        // TODO Auto-generated method stub

    }

    @Override
    public void update() {
        // TODO Auto-generated method stub

    }
    
}

//service方法

package com.wd.service;

import com.wd.dao.DaoI;

public class UserService {
        //使用接口作为new的dao类型
    private DaoI userDao;
    

    public DaoI getUserDao() {
        return userDao;
    }

    public void setUserDao(DaoI userDao) {
        this.userDao = userDao;
    }

    public void register(){
        System.out.println("UserService.register() Service被调用了");
        userDao.add();
    }
    
    public void updateUser(){
        userDao.update();
    }
}

//action 类
public class UserAction {
    private UserService userService;

    public UserService getUserService() {
        return userService;
    }

    public void setUserService(UserService userService) {
        this.userService = userService;
    }
    public String register(){
        userService.register();
        
        return "success";
    }
}
<!--XML配置文件-->

<?xml version="1.0" encoding="UTF-8"?>
<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.xsd">
    <bean id="userAction" class="com.wd.action.UserAction">
        <property name="userService" ref="userService"></property>
    </bean>        
    
    <bean id="userService" class="com.wd.service.UserService">
        <property name="userDao" ref="userDao"></property>
    </bean>
    <!--此userDao相当于DaoI userDao = new MyDaoTest();-->
    <bean id="userDao" class="com.wd.dao.MyDaoTest"></bean>
</beans>

/**
 * 测试类
 * @author Thinkpad
 *
 */
public class Test {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserAction userAction =  (UserAction) ac.getBean("userAction");
        userAction.register();
    }
}

输出结果：