简化相等判断：如何优化Account与UpdateAccount对象差异对比代码？

现有实体类定义 #

Account类 #

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class Account {
    private String id;
    private String section;
    private String name;
    private String type;
    private String username;
}

UpdateAccount类 #

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
public class UpdateAccount {
    private String section;
    private String name;
}

当前属性差异对比实现 #

public class App {
    public static void main(String[] args){
        Account account = new Account("123", "sectionA", "p1", "test", "TestUser1");
        UpdateAccount updateAccount = new UpdateAccount("sectionA", "p11");

        Set<String> diff = new HashSet<>();
        if(!updateAccount.getName().equals(account.getName())){
            diff.add("name");
        }
        if(!updateAccount.getSection().equals(account.getSection())){
            diff.add("section");
        }
        System.out.println(diff);
    }
}

替代实现方案 #

1. 抽取工具方法减少重复代码 #

把属性对比逻辑封装成通用方法，避免重复编写equals判断，同时用Objects.equals规避空指针风险：

import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

public class App {
    public static void main(String[] args){
        Account account = new Account("123", "sectionA", "p1", "test", "TestUser1");
        UpdateAccount updateAccount = new UpdateAccount("sectionA", "p11");

        Set<String> diff = new HashSet<>();
        checkDiff(diff, "name", updateAccount.getName(), account.getName());
        checkDiff(diff, "section", updateAccount.getSection(), account.getSection());
        
        System.out.println(diff);
    }

    private static void checkDiff(Set<String> diffSet, String fieldName, String newValue, String oldValue) {
        if (!Objects.equals(newValue, oldValue)) {
            diffSet.add(fieldName);
        }
    }
}

2. 反射实现通用属性对比 #

如果后续属性频繁新增或修改，反射可以自动遍历UpdateAccount的所有属性，无需手动添加判断逻辑：

import java.lang.reflect.Field;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

public class App {
    public static void main(String[] args){
        Account account = new Account("123", "sectionA", "p1", "test", "TestUser1");
        UpdateAccount updateAccount = new UpdateAccount("sectionA", "p11");

        Set<String> diff = findDiffFields(updateAccount, account);
        System.out.println(diff);
    }

    private static Set<String> findDiffFields(Object updateObj, Object originalObj) {
        Set<String> diffFields = new HashSet<>();
        Field[] updateFields = updateObj.getClass().getDeclaredFields();
        
        for (Field field : updateFields) {
            field.setAccessible(true);
            try {
                Object updateValue = field.get(updateObj);
                Object originalValue = originalObj.getClass().getDeclaredField(field.getName()).get(originalObj);
                
                if (!Objects.equals(updateValue, originalValue)) {
                    diffFields.add(field.getName());
                }
            } catch (NoSuchFieldException | IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return diffFields;
    }
}

注意：反射存在轻微性能开销，适合属性较多且变动频繁的场景。

3. 基于Map映射的属性对比 #

将两个对象的目标属性转成Map，通过遍历键值对完成对比，逻辑直观易懂：

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

public class App {
    public static void main(String[] args){
        Account account = new Account("123", "sectionA", "p1", "test", "TestUser1");
        UpdateAccount updateAccount = new UpdateAccount("sectionA", "p11");

        Map<String, String> updateMap = new HashMap<>();
        updateMap.put("name", updateAccount.getName());
        updateMap.put("section", updateAccount.getSection());

        Map<String, String> originalMap = new HashMap<>();
        originalMap.put("name", account.getName());
        originalMap.put("section", account.getSection());

        Set<String> diff = new HashSet<>();
        for (Map.Entry<String, String> entry : updateMap.entrySet()) {
            if (!Objects.equals(entry.getValue(), originalMap.get(entry.getKey()))) {
                diff.add(entry.getKey());
            }
        }

        System.out.println(diff);
    }
}

内容的提问来源于stack exchange，提问作者xxestter