【java】【反射】反射实现判断发生了修改操作，判断两个对象是否发生属性值的变更，判断两个List集合内对象的属性值是否发生变更

java的反射实现：

判断发生了修改操作，判断两个对象是否发生属性值的变更，判断两个List集合内对象的属性值是否发生变更

今日份代码：

package com.sxd.streamTest;

import java.lang.reflect.Field;
import java.util.*;

/**
 * @ClassName Test
 * @Description 判断发生了修改操作，判断两个对象是否发生属性值的变更，判断两个List集合内对象的属性值是否发生变更
 * @Author sxd
 * @Date 2020/02/14 10:07
 * @Version 1.0
 */
public class Test {

    //忽略的属性
    List<String> ignoreFields = Arrays.asList("yn","id");

    /**
     * 测试的入口方法，实例化几个对象
     */
    @org.junit.Test
   public void test(){
        Date modifyTime = new Date();
        Date modifyTime2 = new Date();

        Student student1 = new Student();
        student1.setAge(1);
        student1.setName("张三1");
        student1.setModifyTime(modifyTime);
        student1.setYn(1);

        Student student2 = new Student();
        student2.setAge(1);
        student2.setName("张三2");
        student2.setModifyTime(modifyTime2);
        student2.setYn(-1);
        List<Student> list1 = Arrays.asList(student1,student2);

        Student student3 = new Student();
        student3.setAge(3);
        student3.setName("张三3");
        student3.setModifyTime(modifyTime);
        student3.setYn(1);

        Student student4 = new Student();
        student4.setAge(4);
        student4.setName("张三4");
        student4.setModifyTime(modifyTime2);
        student4.setYn(-1);

        Student student5 = new Student();
        student5.setAge(4);
        student5.setName("张三4");
        student5.setModifyTime(modifyTime2);
        student5.setYn(11);

        List<Student> list2 = Arrays.asList(student4,student3);

        System.out.println("List集合是否变更：" + listModifyContrast(list2,list1));
        System.out.println("单个对象是否变更：" + objModifyContrast(student5,student4,false));
   }

    /**
     * List数据变更对比
     * @param newList
     * @param oldList
     * @return true有变更 false无变更
     */
   public  Boolean listModifyContrast(List<? extends Object> newList, List<? extends Object> oldList){
       boolean flag = false;
       if (newList != null && oldList != null){
           if (newList.size() != oldList.size()){
               flag = true;
           }else {
               int same = 0;

               for (Object newObj : newList) {
                   for (Object oldObj : oldList) {
                       if (!objModifyContrast(newObj,oldObj,false)){
                           same ++;
                       }
                   }
               }
               if (same != newList.size()){
                   flag = true;
               }
           }
       }else {
           if (newList == null && oldList == null){
               flag = false;
           }else {
               flag = true;
           }
       }
       return flag;
   }

    /**
     * 单个对象-属性修改对比
     * @param newObj
     * @param oldObj
     * @param reset 是否重置属性
     * @return true有变更 false无变更
     */
   public  Boolean objModifyContrast(Object newObj,Object oldObj,boolean reset){
       Map<String, Object> newMap = getReflexMap(newObj);
       Map<String, Object> oldMap = getReflexMap(oldObj);

       int diff = 0;
       for (String field : newMap.keySet()) {
           if (! ignoreFields.contains(field)){
               Object newFieldValue = newMap.get(field);
               Object oldFieldValue = oldMap.get(field);
               if (newFieldValue != null && oldFieldValue != null){
                   if (newFieldValue.equals(oldFieldValue)){
                       if (reset){
                           newMap.put(field,null);
                           oldMap.put(field,null);
                       }
                   }else {
                       diff ++;
                   }
               }else {
                   if (!(newFieldValue == null && oldFieldValue == null)){
                       diff ++;
                   }
               }
           }
       }

       if (diff > 0){
           setReflexObj(newMap, newObj);
           setReflexObj(oldMap, oldObj);
           return true;
       }else {
           return false;
       }
   }

    /**
     * 获取对象的属性名 + 属性值
     * @param obj
     * @return
     */
    public  Map<String,Object> getReflexMap(Object obj){
        Map<String,Object> map = new HashMap<>();

        Class<? extends Object> aClass = obj.getClass();
        Field[] declaredFields = aClass.getDeclaredFields();
        for (Field declaredField : declaredFields) {
            declaredField.setAccessible(true);
            String fieldName = declaredField.getName();
            Object fieldValue = null;
            try {
                fieldValue = declaredField.get(obj);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }

            map.put(fieldName,fieldValue);
        }
        return map;
    }

    /**
     * 设置 对象的 属性名+属性值
     * @param map
     * @return
     */
    public   Object setReflexObj(Map<String,Object> map,Object obj){
        Set<String> fieldSet = map.keySet();
        Class<? extends Object> aClass = obj.getClass();
        for (String field : fieldSet) {
            try {
                Field declaredField = aClass.getDeclaredField(field);
                declaredField.setAccessible(true);
                declaredField.set(obj,map.get(field));
            } catch (NoSuchFieldException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return obj;
    }

}

原文地址：https://www.cnblogs.com/sxdcgaq8080/p/12306433.html