反射+注解

一：属性注解

import java.lang.annotation.*;

/**
 * @author 陆伟
 *
 */
@Target(ElementType.FIELD)  //使用到字段上
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface FruitName {
    String value() default "";
}

类注解

import java.lang.annotation.*;

/**
 * @author 陆伟 
 *
 */
@Target(ElementType.TYPE)  //类注解
@Retention(RetentionPolicy.RUNTIME)  //运行时注解
public @interface AnnoClass {
    String value() default "";
}

方法注解

import java.lang.annotation.*;

@Target({ElementType.PARAMETER, ElementType.METHOD})  //方法注解
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AnnoClassParams {
    Class[] params();
}

 

二：使用

package com.wing.my.cloud.system.modular.system.util.annotation;

import com.wing.my.cloud.system.modular.system.entity.TestUser;
import lombok.*;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;

@Data
@AllArgsConstructor
@NoArgsConstructor
@AnnoClass("类注解")
public class Apple extends Fruit {
    @FruitName("苹果")
    private String appleName;

    @FruitName("红色")
    public String appleColor;

    @AnnoClassParams(params = {TestUser.class})
    public void test() {

    }

    @AnnoClassParams(params = {Thread.class})
    private void test1() {

    }

    public static void main(String[] args) {
        Class<Apple> appleClass = Apple.class;

        Annotation[] annotations = appleClass.getAnnotations();
        List<Annotation> annotations1 = Arrays.asList(annotations);
        annotations1.forEach(annotation -> {
            System.out.println("【类注解】"+annotation);
        });

        //类名
        System.out.println(appleClass.getName());
        //利用反射创建对象
        try {
            Apple apple = appleClass.newInstance();
            apple.setAppleName("橘子");
            System.out.println("【利用反射创建对象】:" + apple);
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }

        /**
         * getDeclaredField 仅能获取类本身的属性成员（包括私有、共有、保护）
         * getDeclaredMethod 得到私有方法
         */
        try {
            Field appleName = appleClass.getDeclaredField("appleName");
            System.out.println("【private 属性】:" + appleName.getName());
            FruitName annotation = appleName.getAnnotation(FruitName.class);
            System.out.println("【private 属性注解】:" + annotation.value());

            Method declaredMethod = appleClass.getDeclaredMethod("test1");
            AnnoClassParams annotation1 = declaredMethod.getAnnotation(AnnoClassParams.class);
            for (int i = 0; i < annotation1.params().length; i++) {
                System.out.println("【private 方法】:" + annotation1.params()[i]);
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }


        /**
         * getField 仅能获取类(及其父类可以自己测试) public属性成员
         * getMethod  public方法
         */
        try {
            Field appleColor = appleClass.getField("appleColor");
            FruitName annotation = appleColor.getAnnotation(FruitName.class);
            System.out.println("【public 属性】" + annotation.value());
            Method test1 = appleClass.getMethod("test");
            AnnoClassParams annotation1 = test1.getAnnotation(AnnoClassParams.class);
            for (int i = 0; i < annotation1.params().length; i++) {
                System.out.println("【public 方法】:" + annotation1.params()[i]);
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }


        Field[] fields = appleClass.getDeclaredFields();
        List<Field> fieldsList = Arrays.asList(fields);
        fieldsList.forEach(field -> {
            System.out.println("【所有的本类的属性】:" + field.getName());
        });

        Field[] fields1 = appleClass.getFields();
        List<Field> fields1List = Arrays.asList(fields1);
        fields1List.forEach(field -> {
            System.out.println("【所有public属性,包含父类的public:】" + field);
        });

        /**
         * getSuperclass().getDeclaredFields()
         * 父类属性
         */
        Field[] declaredFields = appleClass.getSuperclass().getDeclaredFields();
        List<Field> fieldList = Arrays.asList(declaredFields);
        fieldList.forEach(field -> {
            System.out.println("【所有父类的属性】" + field);
        });
        Method[] declaredMethods = appleClass.getDeclaredMethods();
        List<Method> methodList = Arrays.asList(declaredMethods);
        methodList.forEach(method -> {
            System.out.println("【所有方法】:" + method.getName());
        });
    }
}