@Resource和@Component实现零XML配置

1、@Resource的注解：
@Resource是J2EE的注解。意思是说在容器里面找相应的资源。也可以通过name属性指定它name的资源。可以注解到field或者setter上面

public class UserAction {
	private UserService userService;
	
	@Resource(name="userService")
	public void setUserService(UserService userService) {
		this.userService = userService;
	}
	public void addUser(){
		userService.HelloWorld();
	}
}

2、@Component
@Component和<context:component-scan base-package="com.spring"></context:component-scan>配合实现无XML配置，只通过注解配置及可将类放入资源容器中。

案例解析：
1、 xml文件：配置容器资源扫描的包

<?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-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
     
    <context:annotation-config/>
    <!-- 配置容器资源扫描的包 -->
   <context:component-scan base-package="com.spring"></context:component-scan>
</beans>

2、 Java文件：
标注资源的注解@Component。括号里面指定的是存入容器的name属性为userService
那么将来我们拿的时候则getBean(“userService”)即可。如果我们不指定userService它默认存入容器bean的key为userServiceImpl这样就可以得到一个装有UserServiceImpl对象的容器

package com.spring.service;
import org.springframework.stereotype.Component;
import com.spring.dao.UserDao;

@Component("userService")
public class UserServiceImpl implements UserService{
	private UserDao userDao;
	public void init(){
		System.out.println("init");
	}
	public void destory(){
		System.out.println("destory");
	}
	public UserDao getUserDao() {
		return userDao;
	}
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}
	public void HelloWorld(){
		System.out.println("helloworld");
	}
}

通过@Resource将资源注入进来
因为上文已经配置了容器里面的资源。所以我这里将资源通过@Resource注解将资源注入到相关的属性。请看代码：

@Component("userAction")
public class UserAction {
	private UserService userService;
	
	//它会将beans的xml文件配置加入进去
	//也可以使用name属性指定byName的指定
	@Resource(name="userService")
	public void setUserService(UserService userService) {
		this.userService = userService;
	}
	public void addUser(){
		userService.HelloWorld();
	}
}

测试实现：
通过上文配置的userAction案例来得到这个对象然后调用它里面的方法，因为上文通过了@ Component注解将UserAction的对象配置到了容器里面。所以获得容器之后就可以用这种方法getbean即可

	@Test
	public void test01(){
		BeanFactory applicationContext = new ClassPathXmlApplicationContext("beans.xml");
		UserAction user = (UserAction) applicationContext.getBean("userAction");
		user.addUser();
	}

@Scope和@PostConstruct、@PreDestroy

很简单就相当于前面讲到的作用于和initmethod和destorymethod请看下面代码。不再多说：

@Scope("Singleton")
@Component("userService")
public class UserServiceImpl implements UserService{
	private UserDao userDao;
	@PostConstruct
	public void init(){
		System.out.println("init");
	}
	@PreDestroy
	public void destory(){
		System.out.println("destory");
	}
	public UserDao getUserDao() {
		return userDao;
	}
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}
	public void HelloWorld(){
		System.out.println("helloworld");
	}
}