Java自己写一个注解

代码摘自：https://www.cnblogs.com/acm-bingzi/p/javaAnnotation.html

看如下代码：

package com.work.AnnotationTest;

import java.lang.annotation.*;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitName {
    String value() default "";
}

package com.work.AnnotationTest;

import java.lang.annotation.*;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitColor {
    public enum Color{BLUE,RED,GREEN};
    Color fruitColor() default Color.GREEN;
}

package com.work.AnnotationTest;

import java.lang.annotation.*;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitProvider {
    public int id() default -1;
    public String name() default "";
    public String address() default "";
}

package com.work.AnnotationTest;

import java.lang.reflect.Field;

public class FruitInfoUtil {
    public static void getFruitInfo(Class<?> clazz){
        String strFruitName = " 水果名称： ";
        String strFruitColor = " 水果颜色： ";
        String strFruitProvicer = " 供应商信息： ";
        Field[] fields = clazz.getDeclaredFields();
        for (Field field:fields){
            if(field.isAnnotationPresent(FruitName.class)){
                FruitName fruitName = field.getAnnotation(FruitName.class);
                strFruitName = strFruitName+fruitName.value();
                System.out.println(strFruitName);
            }else if (field.isAnnotationPresent(FruitColor.class)){
                FruitColor fruitColor = field.getAnnotation(FruitColor.class);
                strFruitColor = strFruitColor+fruitColor.fruitColor().toString();
                System.out.println(strFruitColor);
            }else if (field.isAnnotationPresent(FruitProvider.class)){
                FruitProvider fruitProvider = field.getAnnotation(FruitProvider.class);
                strFruitProvicer = "供应商编号： "+fruitProvider.id()+" 供应商名称： " + fruitProvider.name() + " 供应商地址： "+fruitProvider.address();
                System.out.println(strFruitProvicer);
            }
        }
    }
}

package com.work.AnnotationTest;

public class FruitRun {
    public static void main(String[] args) {
        FruitInfoUtil.getFruitInfo(Apple.class);
    }
}

输出：

 水果名称： Apple
 水果颜色： RED
供应商编号： 1 供应商名称： 红富士 供应商地址： 上海