注入类型
a) setter(重要)
<?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-2.5.xsd">
<bean id="u" class="com.dao.impl.UserDAOImpl">
</bean>
<bean id="userService" class="com.service.UserService">
<property name="userDAO" ref="u" />
</bean>
</beans>
b) 构造方法
<bean id="userService" class="com.service.UserService">
<!--
<property name="userDAO" ref="u" />
-->
<constructor-arg>
<ref bean="u"/>
</constructor-arg>
</bean>
c) 接口注入