注解类详解

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核心注解类TestAnnotation.java

package annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

//元注解
@Retention(RetentionPolicy.RUNTIME)
//注解可以应用于方法上和类上
@Target({ElementType.METHOD,ElementType.TYPE})
public @interface TestAnnotation {
	//属性(default 默认值)
	String color() default "blue";
	String value();
	int[] arr();
	TrafficLamp tl() default TrafficLamp.GREEN;
	//注解属性
	MetaAnnotation metaAnno() default @MetaAnnotation("sss");
	Class clazz() default String.class;

}

方法上定义注解AnnotationMethodTest.java

package annotation;

import org.junit.Test;

//方法上定义注解
public class AnnotationMethodTest {
	@Test
	@TestAnnotation(value = "methodTest",arr = {1,2,3},tl = TrafficLamp.RED,metaAnno = @MetaAnnotation("abc"),clazz = Integer.class)
	public void test_1(){
		if(AnnotationTest.class.isAnnotationPresent(TestAnnotation.class)){
			TestAnnotation ta = AnnotationTest.class.getAnnotation(TestAnnotation.class);
			System.out.println(ta);
			System.out.println(ta.getClass());
			System.out.println(ta.value());
			System.out.println(ta.arr().length);
			System.out.println(ta.tl());
			System.out.println(ta.metaAnno().value());
		}
		
	}
}

类上定义注解及测试类

package annotation;

import org.junit.Test;

//只有value属性声明的时候可以省略"value="
@TestAnnotation(value = "test",arr = {1,2,3},tl = TrafficLamp.RED,metaAnno = @MetaAnnotation("abc"),clazz = Integer.class)
public class AnnotationTest {
	@Test
	public void test_1() throws Exception{
		if(AnnotationTest.class.isAnnotationPresent(TestAnnotation.class)){
			TestAnnotation ta = AnnotationTest.class.getAnnotation(TestAnnotation.class);
			System.out.println(ta);
			System.out.println(ta.getClass());
			System.out.println(ta.value());
			System.out.println(ta.arr().length);
			System.out.println(ta.tl());
			System.out.println(ta.metaAnno().value());
		}
		AnnotationMethodTest amt = new AnnotationMethodTest();
		if(amt.getClass().getMethod("test_1").isAnnotationPresent(TestAnnotation.class)){		
			TestAnnotation ta = amt.getClass().getMethod("test_1").getAnnotation(TestAnnotation.class);
			System.out.println(ta);
			System.out.println(ta.getClass());
			System.out.println(ta.value());
			System.out.println(ta.arr().length);
			System.out.println(ta.tl());
			System.out.println(ta.metaAnno().value());		
		}
	}
}

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