【spring框架】spring的几个Annotation实现(下)

继续上一篇http://blog.csdn.net/acmman/article/details/43889483的介绍

3.注解@Required

是初始化的时候就给注入，检查这个配置是否有问题。用来容错的。

4.@Resource(重要)

a)加入：j2ee/common-annotation.jar

@Resource是j2ee的标准。

b)默认按名称，名称找不到，按类型(比AutoWired更直观)

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-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
               
  <context:annotation-config/>
  
  <bean id="u" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="1"></property>
  </bean>
	
  <bean id="userService" class="cn.edu.hpu.service.UserService">
  </bean>
  
</beans>

UserService.java:

package cn.edu.hpu.service;


import javax.annotation.Resource;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserService {


	private UserDao userDao;
	
	public void init(){
		System.out.println("init");
	}
	
	public UserDao getUserDao() {
		return userDao;
	}
	@Resource
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}


	public void add(User u){
		this.userDao.save(u);
	}
	
	public void destroy(){
		System.out.println("destroy");
	}
	
}

测试：

package cn.edu.hpu.service;
import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserServiceTest {
	
	@Test
	public void testAdd() throws Exception{
		ClassPathXmlApplicationContext ctx=new 


ClassPathXmlApplicationContext("beans.xml");
		
		UserService userService=(UserService)ctx.getBean("userService");
		System.out.println(userService.getUserDao());
		ctx.destroy();
	}
}

结果:

daoid=1

c)可以指定特定名称

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-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
               
  <context:annotation-config/>
  
  <bean id="u" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="1"></property>
  </bean>
  <bean id="u2" class="cn.edu.hpu.dao.Impl.UserDaoImpl">
     <property name="daoId" value="2"></property>
  </bean>
	
  <bean id="userService" class="cn.edu.hpu.service.UserService">
  </bean>
  
</beans>

UserService.java中改一下这里

@Resource(name="u2")
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}

测试:

package cn.edu.hpu.service;
import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserServiceTest {
	
	@Test
	public void testAdd() throws Exception{
		ClassPathXmlApplicationContext ctx=new 


ClassPathXmlApplicationContext("beans.xml");
		
		UserService userService=(UserService)ctx.getBean("userService");
		System.out.println(userService.getUserDao());
		ctx.destroy();
	}
}

结果:

daoid=2

d)推荐使用

原因是比比AutoWired更直观

e)不足:如果没有源码，就无法运用annotation，只能用xml.

5.@Component(spring自带)

如果不想在beans.xml里面写bean了，想一劳永逸，让spring去指定包下去寻找，那么就用

<context:component-scan base-package=”XXXX”>其中”XXXX”就是指定的包名。

实验:

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-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
               
  <context:annotation-config/>
  <context:component-scan base-package="cn.edu.hpu"/>
  <bean id="userService" class="cn.edu.hpu.service.UserService">
  </bean>
  
</beans>

UserDaoImpl.java:

package cn.edu.hpu.dao.Impl;


import java.util.List;
import java.util.Map;
import java.util.Set;


import org.springframework.stereotype.Component;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


@Component
public class UserDaoImpl implements UserDao{


	public void save(User u) {
	    System.out.println("add success!!");		
	}
}

测试:

package cn.edu.hpu.service;
import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserServiceTest {
	
	@Test
	public void testAdd() throws Exception{
		ClassPathXmlApplicationContext ctx=new 


ClassPathXmlApplicationContext("beans.xml");
		
		UserService userService=(UserService)ctx.getBean("userService");
		User u=new User();
		u.setUsername("u1");
		u.setPassword("p1");
		userService.add(u);
		ctx.destroy();
	}
}

结果:

add success!!

a)初始化的名字默认为类名字母小写

推荐写上名字

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-2.5.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context-2.5.xsd">
               
  <context:annotation-config/>
  <context:component-scan base-package="cn.edu.hpu"/>
</beans>

UserService.java：

package cn.edu.hpu.service;


import javax.annotation.Resource;


import org.springframework.stereotype.Component;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


@Component("userService")
public class UserService {


	private UserDao userDao;
	
	public void init(){
		System.out.println("init");
	}
	
	public UserDao getUserDao() {
		return userDao;
	}
	@Resource(name="u")
	public void setUserDao(UserDao userDao) {
		this.userDao = userDao;
	}


	public void add(User u){
		this.userDao.save(u);
	}
	
	public void destroy(){
		System.out.println("destroy");
	}
	
}

UserDaoImpl.java:

package cn.edu.hpu.dao.Impl;


import java.util.List;
import java.util.Map;
import java.util.Set;


import org.springframework.stereotype.Component;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


@Component("u")
public class UserDaoImpl implements UserDao{


	public void save(User u) {
	    System.out.println("add success!!");		
	}
}

测试：

package cn.edu.hpu.service;
import org.junit.Test;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


import cn.edu.hpu.dao.UserDao;
import cn.edu.hpu.model.User;


public class UserServiceTest {
	
	@Test
	public void testAdd() throws Exception{
		ClassPathXmlApplicationContext ctx=new 


ClassPathXmlApplicationContext("beans.xml");
		
		UserService userService=(UserService)ctx.getBean("userService");
		User u=new User();
		u.setUsername("u1");
		u.setPassword("p1");
		userService.add(u);
		ctx.destroy();
	}
}

结果:

add success!!

b)可以指定初始化bean的名字

目前@Component、@Repository(数据仓库)、@Service、@Controller没有区别

有源码用Annotation方便，开发效率高，没源码用XML。

尊重开源精神，尊重劳动成果，转载请注明出处:http://blog.csdn.net/acmman/article/details/43889503

发布者：全栈程序员-用户IM，转载请注明出处：https://javaforall.cn/109545.html原文链接：https://javaforall.cn

【正版授权，激活自己账号】： Jetbrains全家桶Ide使用，1年售后保障，每天仅需1毛

【官方授权正版激活】： 官方授权正版激活支持Jetbrains家族下所有IDE 使用个人JB账号...