Spring 中的注解
1、普通方式注解
a、在配置文件中配置
1、导入命名空间
xmlns:context="http://www.springframework.org/schema/context"
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
2、到入依赖注入的注解解析器
<context:annotation-config></context:annotation-config>
3、把student和person导入进来
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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:annotation-config> <bean id="student" class="cn.test.annotation2.Student"></bean> <bean id="person" class="cn.test.annotation2.Person"></bean> </beans>
b、再类中添加注解@Resource--字段注解 @PostConstruct--初始化注解 @PreDestroy--销毁注解
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
package cn.test.annotation2; import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; import javax.annotation.Resource; public class Person { private Long pid; @Resource(name="student") //@Autowired//按照类型进行匹配 //@Qualifier("student") private Student student; public void say(){ this.student.say(); } @PostConstruct public void init(){ System.err.println("Person Init"); } @PreDestroy public void destory(){ System.err.println("Person distory"); } }
c、测试
原理
启动spring容器,并且加载配置文件会为student和person两个类创建对象
当解析到<context:annotation-config></context:annotation-config>会启动依赖注入的注解解析器
会在纳入spring管理的bean的范围内查找看哪些bean的属性上有@Resource注解
如果@Resource注解的name属性的值为"",则会把注解所在的属性的名称和spring容器中bean的id进行匹配如果匹配成功,则把id对应的对象赋值给该属性,如果匹配不成功,则按照类型进行匹配,如果再匹配不成功,则报错
如果@Resource注解的name属性的值不为"",会把name属性的值和spring容器中bean的id做匹配,如果匹配成功,则赋值,如果匹配不成功 ,则直接报错
说明:
注解只能用于引用类型
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
@Test public void dosome(){ ClassPathXmlApplicationContext applicationContext=new ClassPathXmlApplicationContext("cn/test/annotation2/applicationContext.xml"); Person person= (Person) applicationContext.getBean("person"); person.say(); applicationContext.close(); }
2、扫描注解
1、配置
1、导入命名空间
xmlns:context="http://www.springframework.org/schema/context"
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
2、 component就是bean
base-package
会在base-package的值所在的包及子包下扫描所有的类
<context:component-scan base-package="cn.test.annotation.scan"></context:component-scan>
2、在类中添加注释
@Component
public class Person {
@Resource
private Student student;
}
3、测试
原理
启动spring容器,加载配置文件
spring容器解析到
<context:component-scan base-package="cn.test.annotation.scan"></context:component-scan>
spring容器会在指定的包及子包中查找类上是否有@Component
如果@Component注解没有写任何属性
@Component
public class Person{ }
==
<bean id="person" class="..Person">
如果@Component("aa")
@Component
public class Person{ }
==
<bean id="aa" class="..Person">
在纳入spring管理的bean的范围内查找@Resource注解
执行@Resource注解的过程
说明:
xml效率比较高,但是书写比较麻烦
注解效率比较低,书写比较简单