【spring框架】spring的几个Annotation实现(上)

spring除了XML的配置，还可以用Annotation注解来实现spring的配置功能，下面来介绍里面一些配置方法

1.Annotation第一步

a)修改xml文件，参考文档<context:annotation-config/>

基于注解（Annotation-based）的配置

在 Spring 2.5中已经可以用注解的方式去驱动 Spring 的依赖注射了。更重要的是，@Autowired注解提供了与第 3.3.5 节 “自动装配（autowire）协作者”一节中描述的同样功能，并且提供了更细致的控制与更好的适应性。Spring 2.5 也支持 JSR-250 中的一些注解，例如@Resource，@PostConstruct，以及@PreDestroy。

<?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/>     </beans>

（加载了<context:annotation-config/>就相当于隐式注册 post-processors， 包括了 AutowiredAnnotationBeanPostProcessor，CommonAnnotationBeanPostProcessor，PersistenceAnnotationBeanPostProcessor，也包括了前面提到的RequiredAnnotationBeanPostProcessor四个bean，用来完成注解的加载）
加了:xmlns:context="http://www.springframework.org/schema/context"
与<context:annotation-config/>
xsd定义了它所控制的xml都能写什么，就是我们当前文件的命名空间(装着我能写的名字)


2.Autowired
a)默认按类型by type

例子：

<?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>

注意，此时userService的bean里面并没有加id=u的bean。我们用注解来进行AutoWired
在UserService的getUserDao方法上面加注解@Autowired(默认byType)

package cn.edu.hpu.service;import org.springframework.beans.factory.annotation.Autowired;import cn.edu.hpu.dao.UserDao;import cn.edu.hpu.dao.Impl.UserDaoImpl;import cn.edu.hpu.model.User;public class UserService {private UserDao userDao;public void init(){System.out.println("init");}public UserDao getUserDao() {return userDao;}@Autowiredpublic 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();}}

UserDaoImpl.java:改写了toString方法，返回daoId

package cn.edu.hpu.dao.Impl;import java.util.List;import java.util.Map;import java.util.Set;import cn.edu.hpu.dao.UserDao;import cn.edu.hpu.model.User;public class UserDaoImpl implements UserDao{private int daoId;public int getDaoId() {return daoId;}public void setDaoId(int daoId) {this.daoId = daoId;}public void save(User u) {    System.out.println("add success!!");}@Overridepublic String toString() {return "daoid="+daoId;}}

测试结果:
daoid=1
也就是用Annotation也可以实现Autowired


b)如果想用byName,使用@Qulifier


如果有好几个Type一样的，就应该用byName了：

<?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>

在UserService的getUserDao方法的参数前加@Qualifier("XX")，其中
"XX"是相应bean的id
UserService.java:

package cn.edu.hpu.service;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import cn.edu.hpu.dao.UserDao;import cn.edu.hpu.dao.Impl.UserDaoImpl;import cn.edu.hpu.model.User;public class UserService {private UserDao userDao;public void init(){System.out.println("init");}public UserDao getUserDao() {return userDao;}@Autowiredpublic void setUserDao(@Qualifier("u2")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=2
说明注解@Qualifier("u2")起到了作用


c)写在private filed(第三种输入形式)(不建议，破坏封装)
@Autowired(required=false)就是可以去自动获取，如果没有也可以不要(可有可无)


d)如果写在set上，@qualifier需要写在参数上


补充：
前面在XML中提到的ini-method和的destroy-method用注解实现就是在相应方法上加：
@PostConstruct与@PreDestroy

@Scope("XXX")里面指定是用什么样的生命范围(singleton、prototype)

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