Spring3注入类型（Injection Type)

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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.xsdhttp://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.xsdhttp://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）