java反射和注解

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参考教材地址

http://wiki.jikexueyuan.com/project/java-reflection/java-at.html

注解的定义与接口的定义相似，下面是MyAnnotation注解的定义：

package 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 MyAnnotation {public String name();public String value();}

类注解

package annotation;@MyAnnotation(name = "someName",value = "Hello Word")public class TheClass {}

package annotation;public class TwoClass {@MyAnnotation(name = "twoName",value = "Hello Two")public void doSomething(){}}

main方法

package annotation;import java.lang.annotation.Annotation;import java.lang.reflect.Method;public class Demo1 {public static void main(String[] args) {Class aClass = TheClass.class;//指定访问所有类的注解Annotation[] annotations = aClass.getAnnotations();for (Annotation annotation:annotations) {if (annotation instanceof MyAnnotation) {MyAnnotation annotation2 = (MyAnnotation) annotation;System.out.println("name:" + annotation2.name());System.out.println("value:" + annotation2.value());}}System.out.println("---------------------");//指定访问一个类的注解Class bClass = TheClass.class;Annotation myAnnotation = bClass.getAnnotation(MyAnnotation.class);if (myAnnotation instanceof MyAnnotation) {MyAnnotation annotation2 = (MyAnnotation) myAnnotation;System.out.println("name:" + annotation2.name());System.out.println("value:" + annotation2.value());}System.out.println("---------------------");try {Method method = TwoClass.class.getMethod("doSomething");Annotation[] annotations2 = method.getDeclaredAnnotations();//Annotation annotation = method.getAnnotation(MyAnnotation.class);获取指定方法的注解for (Annotation annotation:annotations2) {if (annotation instanceof MyAnnotation) {MyAnnotation myAnnotation2 = (MyAnnotation) annotation;        System.out.println("name: " + myAnnotation2.name());        System.out.println("value: " + myAnnotation2.value());}}} catch (NoSuchMethodException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (SecurityException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

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