1 <?xml version="1.0" encoding="UTF-8"?> 2 <beans 3 xmlns="http://www.springframework.org/schema/beans" 4 xmlns:context="http://www.springframework.org/schema/context" 5 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 6 xmlns:p="http://www.springframework.org/schema/p" 7 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"> 8 9 <context:annotation-config /> 10 <bean id="userDao" class="com.bxw.dao.impl.UserDaoImpl" /> 11 <bean id="userService" class="com.bxw.service.UserService" lazy-init="true" scope="singleton" init-method="init" destroy-method="destroy"/> 12 13 </beans>
applicationContext.xml
xmlns(xml命名空间):其实就是指定该xml的格式,能够用哪些标签。
需要添加xmlns:context="http://www.springframework.org/schema/context"
和xsi:schemaLocation中添加
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd"
applicationContext.xml需要添加<context:annotation-config />,这会初始化4个用来处理一些注解的bean
1 package com.bxw.service; 2 3 import org.springframework.beans.factory.annotation.Autowired; 4 import org.springframework.beans.factory.annotation.Qualifier; 5 6 import com.bxw.dao.UserDao; 7 import com.bxw.dao.impl.UserDaoImpl; 8 import com.bxw.po.User; 9 10 public class UserService { 11 private UserDao userDao = new UserDaoImpl(); 12 13 public void init() { 14 System.out.println("init..."); 15 } 16 17 public UserDao getUserDao() { 18 return userDao; 19 } 20 21 @Autowired 22 public void setUserDao(@Qualifier("userDao") UserDao userDao) { 23 this.userDao = userDao; 24 } 25 26 public void add(User u){ 27 this.userDao.save(u); 28 } 29 30 public void destroy() { 31 System.out.println("destroy..."); 32 } 33 34 }
UserService.java
@Autowire一般注解在set方法上,会采用bytype的方式注入(虽然它可以注解在各种方法甚至是成员变量上,但不常用)
采用bytype方式注入会发生一些问题,例如如果配置了名字(id)不同但class相同的两个bean,这个时候将会报错,采用@Qualifier解决。
@Qualifier可以在bean中进行配置,如果没有配置的且指定了该bean的id,则id值即为qualifier的默认值。(这也解释了UserService.java中为什么是@Qualifier("userDao")).
时间: 2024-10-24 00:07:03