【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;
}
@Autowired
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();
}
}
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!!");
}
@Override
public 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;
}
@Autowired
public 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 {
@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
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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