【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;}@Resourcepublic 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 {@Testpublic 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 {@Testpublic 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;@Componentpublic 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 {@Testpublic 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 {@Testpublic 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。

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