在进行类或方法定义的时候，都可以使用一系列的Annotation（public interface Annotation）进行声明，如果想要获取这些Annotation的信息，可以直接通过反射来完成。在 java.lang.reflect 里面有一个AccessibleObject类，在本类中提供有Annotation类的方法：
1.获取全部Annotation：public Annotation[] getAnnotations();
2.获取指定Annotation：public <T extends Annotation> T getAnnotation(Class<T> annotationClass)
package com.annotation.demo;import java.io.Serializable; import java.lang.annotation.Annotation; import java.lang.reflect.Method;@FunctionalInterface @Deprecated(forRemoval = false,since = "1.1") interface IMessage{public void send(String msg); }@SuppressWarnings("serial") class MessageImpl implements IMessage,Serializable{@Override@Deprecated(since = "1.3")public void send(String msg) {System.out.println("【消息发送】" + msg);} }public class annotationdemo {public static void main(String[] args) throws Exception {{System.out.println("-----------------------IMessage接口：-----------------------------");Annotation annotations[] = IMessage.class.getAnnotations();//获取接口上的全部Annotationfor(Annotation annotation:annotations){System.out.println(annotation);}}{System.out.println("-----------------------MessageImpl子类：-----------------------------");Annotation annotations[] = MessageImpl.class.getAnnotations();//获取MessageImpl子类上的全部Annotationfor(Annotation annotation:annotations){System.out.println(annotation);}}{System.out.println("-----------------------send()方法：-----------------------------");Method method = MessageImpl.class.getDeclaredMethod("send", String.class);Annotation annotations[] = method.getAnnotations();//获取send方法上的全部Annotationfor(Annotation annotation:annotations){System.out.println(annotation);}}} }
不同的Annotation有不同的作用范围：
| Annotation名称 | 作用范围 |
@SuppressWarnings | @Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE, MODULE}) @Retention(RetentionPolicy.SOURCE) public @interface SuppressWarnings {} |
@FunctionalInterface | @Documented @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) public @interface FunctionalInterface {} |
@Deprecated | @Documented @Retention(RetentionPolicy.RUNTIME) @Target(value={CONSTRUCTOR, FIELD, LOCAL_VARIABLE, METHOD, PACKAGE, MODULE, PARAMETER, TYPE}) |
