创建spring自定义注解进行自动装配

Posted 2020-08-16

1、创建自定义注解

 1 import org.springframework.beans.factory.annotation.Qualifier;
 2 import java.lang.annotation.ElementType;
 3 import java.lang.annotation.Retention;
 4 import java.lang.annotation.RetentionPolicy;
 5 import java.lang.annotation.Target;
 6 
 7 
 8 @Target({ElementType.FIELD,ElementType.PARAMETER,ElementType.TYPE})
 9 @Retention(RetentionPolicy.RUNTIME)
10 @Qualifier
11 public @interface StringedInstrument {
12 
13 }

View Code

Retention注解有一个属性value，是RetentionPolicy类型的，Enum RetentionPolicy是一个枚举类型，

用@Retention(RetentionPolicy.CLASS)修饰的注解，表示注解的信息被保留在class文件(字节码文件)中当程序编译时，但不会被虚拟机读取在运行的时候；
用@Retention(RetentionPolicy.SOURCE )修饰的注解,表示注解的信息会被编译器抛弃，不会留在class文件中，注解的信息只会留在源文件中；
用@Retention(RetentionPolicy.RUNTIME )修饰的注解，表示注解的信息被保留在class文件(字节码文件)中当程序编译时，会被虚拟机保留在运行时，

2、创建instrument ，并使用注解

 

1 @StringedInstrument
2 public class Instrument {
3 
4     public void play() {
5         System.out.println("playing...");
6     }
7 }

 

3、创建表演者kenny,进行自动装配

 1 import org.springframework.beans.factory.annotation.Autowired;
 2 
 3 public class Kenny {
 4 
 5     @Autowired
 6     @StringedInstrument
 7     private Instrument instrument;
 8 
 9     public Instrument getInstrument() {
10         return instrument;
11     }
12 
13     public void setInstrument(Instrument instrument) {
14         this.instrument = instrument;
15     }
16 
17 
18     public Kenny(Instrument instrument) {
19         this.instrument = instrument;
20     }
21 
22     public void  perform(){
23         instrument.play();
24     }
25 }

4、配置spring

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4        xmlns:context="http://www.springframework.org/schema/context"
 5        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
 6 
 7     <context:annotation-config></context:annotation-config>
 8 
 9     <bean id="kenny" class="Kenny">
10     </bean>
11 
12     <bean id="instrument" class="Instrument">
13 
14     </bean>
15 
16 </beans>

5、测试

 1 import org.springframework.context.ApplicationContext;
 2 import org.springframework.context.support.ClassPathXmlApplicationContext;
 3 
 4 
 5 public class Test {
 6     public static void main(String[] args) {
 7 
 8         ApplicationContext context = new ClassPathXmlApplicationContext("context.xml");
 9         Kenny kenny = (Kenny) context.getBean("kenny");
10         kenny.perform();
11     }
12 }