spring注入类型

<?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-3.0.xsd"> 
<!-- <bean name="u" class="com.bjsxt.dao.impl.UserDAOImpl"> -->
<bean id="u" class="com.bjsxt.dao.impl.UserDAOImpl">
<!-- collaborators and configuration for this bean go here -->
</bean>

<bean id="userService" class="com.bjsxt.service.UserService">
<!-- setter注入 -->
<!--  <property name="userDAO" ref="u"> </property>-->

<!-- 构造注入 -->
<constructor-arg>
<ref bean="u"></ref>
</constructor-arg>

</bean>
<!-- more bean definitions go here -->
</beans>