从JDK1.5之后，注解在各大框架上得到了广泛的应用。下面这个例子中，你可以判断一个类或者方法或者字段上有没有注解，以及怎么获取上面的注解值。话不多说，代码如下：

AnnotationTest01.java

package com.zkn.newlearn.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.METHOD,ElementType.PARAMETER})
public @interface AnnotationTest01 {String color();
}

AnnotationTest02.java

package com.zkn.newlearn.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface AnnotationTest02 {String getUserName();
}

AnnotationTest04.java

package com.zkn.newlearn.annotation;import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE,ElementType.FIELD})
public @interface AnnotationTest04 {String getAddress();
}

AnnotationTest03.java

package com.zkn.newlearn.annotation;import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;/*** 测试Annotation* @author zkn**/
@AnnotationTest02(getUserName="zhangsan")
public class AnnotationTest03 {@AnnotationTest01(color="red")public static String testColor(String color){System.out.println(color);return color;}@AnnotationTest04(getAddress="北京市海淀区")String address;public static void main(String[] args) {//获取方法上的注解值Method[] methods = AnnotationTest03.class.getDeclaredMethods();if(methods != null){for(Method method : methods){AnnotationTest01 annotation = method.getAnnotation(AnnotationTest01.class);if(annotation == null)continue;Method[] me = annotation.annotationType().getDeclaredMethods();for(Method meth : me){try {String color = (String) meth.invoke(annotation,null);System.out.println(color);} catch (IllegalAccessException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}}}}//获取类上的注解值AnnotationTest02 anno = AnnotationTest03.class.getAnnotation(AnnotationTest02.class);if(anno != null){Method[] met = anno.annotationType().getDeclaredMethods();for(Method me : met ){if(!me.isAccessible()){me.setAccessible(true);}try {System.out.println(me.invoke(anno, null));} catch (IllegalAccessException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}}}//获取字段上的注解值AnnotationTest03 noon = new AnnotationTest03();Field[] field = AnnotationTest03.class.getDeclaredFields();if(field != null){for(Field fie : field){if(!fie.isAccessible()){fie.setAccessible(true);}AnnotationTest04 annon = fie.getAnnotation(AnnotationTest04.class);Method[] meth = annon.annotationType().getDeclaredMethods();for(Method me : meth){if(!me.isAccessible()){me.setAccessible(true);}try {//给字段重新赋值fie.set(noon, me.invoke(annon, null));System.out.println(fie.get(noon));} catch (IllegalAccessException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}}}}}
}