Java 注解

Posted 2022-11-12 猪八戒1.0

 

[public] @interface 注解名
   // 定义属性
   数据类型 属性名() [default 属性值];

 

 

package org.lanqiao.annotation;

import java.lang.annotation.ElementType;

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

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)


public @interface FruitColor

    String fruitColor() default "RED";

package org.lanqiao.annotation;

import java.lang.annotation.ElementType;

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

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)


public @interface FruitName

    String value() default "fruit";

package org.lanqiao.annotation;

import java.lang.annotation.ElementType;

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

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)


public @interface FruitProvider

    int id() default 1;
    String name() default "苹果集团";

    String address() default "洪山区";

package org.lanqiao.entity;


import org.lanqiao.annotation.FruitColor;
import org.lanqiao.annotation.FruitName;
import org.lanqiao.annotation.FruitProvider;



public class Apple 
    @FruitName(value = "Apple")
    public  String appleName;

    @FruitColor(fruitColor = "RED")
    public String appleColor;

    @FruitProvider(id=1,name="陕西红富士集团",address = "陕西省西安市未央区红富士大厦")
    public String appleProvider;

package org.lanqiao.annotation.test;
import org.lanqiao.annotation.FruitColor;
import org.lanqiao.annotation.FruitName;
import org.lanqiao.annotation.FruitProvider;

import java.lang.reflect.Field;


/**
 * 使用反射机制处理自定义注解
 */
public class FruitInfoUtil 

    public static void main(String[] args) throws Exception 

        // 加载 AnnotationTest.class类
        Class<?> clazz = FruitInfoUtil.class.getClassLoader().loadClass("org.lanqiao.entity.Apple");
        // 获取属性
        Field[] fields = clazz.getDeclaredFields();
        // 遍历属性

        for (Field field : fields) 
            FruitName fn = field.getAnnotation(FruitName.class);
            FruitColor fc = field.getAnnotation(FruitColor.class);
            FruitProvider fp = field.getAnnotation(FruitProvider.class);
            if(fn!=null)
                System.out.println("水果名称：" + fn.value());
            
            if(fc!=null)
                System.out.println("水果颜色：" + fc.fruitColor() );
            
            if(fp!=null)
                System.out.println("水果供应商：供应商编号："+fp.id()+"；供应商名称："+fp.name()+"；供应商地址："+fp.address());