注入类型分为三种： 

a)     setter（常用）

package com.bebig.service;

import com.bebig.dao.UserDAO;
import com.bebig.model.User;

//逻辑业务层
public class UserService {
    private UserDAO userDAO;

    public void add(User u) {
        userDAO.save(u);

    }

    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }

    public UserDAO getUserDAO() {
        return userDAO;
    }
}

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<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-3.0.xsd
http://www.springframework.org/schema/context 
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- a service object; we will be profiling its methods -->
    <bean id="u" class="com.bebig.dao.impl.UserDAOImpl" />
    <bean id="userService" class="com.bebig.service.UserService">
    <!-- 通过userDAO的setter方法将u注入 -->
        <property name="userDAO" ref="u" />
    </bean>

</beans>


b)     构造方法（少用）

package com.bebig.service;

import com.bebig.dao.UserDAO;
import com.bebig.model.User;
//逻辑业务层
public class UserService {
    //构造函数里有一个userDAO对象需要初始化
    public UserService(UserDAO userDAO) {
        super();
        this.userDAO = userDAO;
    }

    private UserDAO userDAO;

    public void add(User u) {
        userDAO.save(u);

    }

    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }

    public UserDAO getUserDAO() {
        return userDAO;
    }
}

beans.xml

 

<?xml version="1.0" encoding="UTF-8"?>
<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-3.0.xsd
http://www.springframework.org/schema/context 
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- a service object; we will be profiling its methods -->
    <bean id="u" class="com.bebig.dao.impl.UserDAOImpl" />
    <bean id="userService" class="com.bebig.service.UserService">
    <!-- 构造函数指定注入bean -->
        <constructor-arg>
            <ref bean="u" />
        </constructor-arg>
    </bean>

</beans>


c)     接口注入（少用）