spring的依赖注入DI(IOC)

1、手动注入

（1）set注入

public class UserService {

    private UserDao userDao;

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

    <bean id="userDao1" class="com.spring1.dao.UserDao"></bean>

    <bean id="userService" class="com.spring1.service.UserService">
        <property name="userDao" ref="userDao1"></property>
    </bean>
    

通过userService对象的setUserDao方法，将userDao1注入进去。

public class User {
    int id;
    String name;
    String password;
    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 String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

public class UserDao {

    public void setShowUser(User user){
        System.out.println(user.getId()+":"+user.getName()+":"+user.getPassword());
    }
}

    <bean id="user" class="com.spring1.entity.User">
        <property name="id" value="1"></property>
        <property name="name" value="zhangsan"></property>
        <property name="password" value="123456"></property>
    </bean>

    <bean id="userDao1" class="com.spring1.dao.UserDao">
        <property name="showUser" ref="user"></property>
    </bean>

在bean配置中对user初始化，userDao1通过自己的setShowUser方法将user注入

（2）构造方法注入

    <bean id="userDao1" class="com.spring1.dao.UserDao">
    </bean>

    <bean id="testService" class="com.spring1.service.UserService">
        <constructor-arg name="userDao1" ref="userDao1"></constructor-arg>
    </bean>

    @Test
    public void test() {

        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = (UserService) ac.getBean("testService");
        service.showUser();
    }

public class UserService {

    private UserDao userDao;

    public UserService(UserDao userDao1){
        this.userDao = userDao;
    }

    public void showUser(){
        System.out.print("ok-------------");
    }

}

构造函数参数的名字，要与类的构造参数的名字对应。

2、自动注入

    <bean id="userDao2" class="com.spring1.dao.UserDao"></bean>

    <bean id="testService" class="com.spring1.service.UserService" autowire="byName">
    </bean>

id=userDao2，下边的setUserDao2==userDao2是一样的。

public class UserService {

    private UserDao userDao;

    public void setUserDao2(UserDao userDao1){
        this.userDao = userDao1;
    }

    public void showUser(){
       userDao.showUser();
    }

}

byname自动注入的时候，就要顶一个一个name=类中的参数名字的bean