Java：比較兩個物件中全部屬性值是否相等

例如下述Java類：

import java.io.Serializable;
import java.util.List;

public class Bean_Topology implements Serializable {
	private static final long serialVersionUID = 1L;
	public static long getSerialversionuid() {
		return serialVersionUID;
	}

	private Long topology_pk;

	private String topology_id;

	public String getTopology_id() {
		return topology_id;
	}

	public void setTopology_id(String topology_id) {
		this.topology_id = topology_id;
	}

	public Long getTopology_pk() {
		return topology_pk;
	}

	public void setTopology_pk(Long topology_pk) {
		this.topology_pk = topology_pk;
	}

	@Override
	public String toString() {
		return "當前拓撲的PK為：" + topology_pk + "，ID為：" + topology_id;
	}
}
 

如下想判斷下面兩個物件中全部屬性值是否一致時，有哪些辦法呢？

Bean_Topology topology1 = new Bean_Topology();
	topology1.setTopology_id("1");

Bean_Topology topology2 = new Bean_Topology();
	topology2.setTopology_pk(1L);
	topology2.setTopology_id("1");

方法一：重寫Bean_Topology的equals方法和hashcode方法，程式碼如下：

@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
		
    if (obj == null || getClass() != obj.getClass()) {
        return false;
     }

    Bean_Topology topology = (Bean_Topology) obj;
    if (topology_pk == null) {
        if (topology.topology_pk != null) {
            return false;
        } 
    }else if (!topology_pk.equals(topology.topology_pk)) {
        return false;	
    }
        
    if (topology_id == null) {
        if (topology.topology_id != null) {
            return false;
        } 
    }else if (!topology_id.equals(topology.topology_id)) {
        return false;	
    }
        
        return true;
    }
	
    @Override
    public int hashCode() {
        return  topology_pk.hashCode()+topology_id.hashCode();
    }
 

測試程式碼如下：

if(topology1.equals(topology2)) {
	System.out.println("物件1與物件2的屬性值無差異。");
}else {
	System.out.println("物件1與物件2的屬性值有差異。");	
}

輸出結果為：

物件1與物件2的屬性值有差異。

方法二：呼叫文章末尾的工具類，程式碼如下：

Map<String, Map<String,Object>> resultMap=compareFields(topology1,topology2);
int size=resultMap.size();
if(size>0) {
    System.out.println("物件1與物件2的屬性值有差異,差異結果如下：");
		
    Iterator<String> it = resultMap.keySet().iterator();
    while(it.hasNext()) {
        String key=it.next();
        System.out.println("  "+key+"(oldValue:"+resultMap.get(key).get("oldValue")+",newValue:"+resultMap.get(key).get("newValue")+")");
        }	
}else {
	System.out.println("物件1與物件2的屬性值無差異！");
}
 

輸出結果為：

物件1與物件2的屬性值有差異,差異結果如下：
  topology_pk(oldValue:null,newValue:1)

工具類如下：

package com.sitech.modual.util.compare;

import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import com.sitech.modual.bean.Bean_Link;
import com.sitech.modual.bean.Bean_Topology;

public class ClassCompareUtil {
	/**
	 * 比較兩個實體屬性值，返回一個boolean,true則表時兩個物件中的屬性值無差異
	 * @param oldObject 進行屬性比較的物件1
	 * @param newObject 進行屬性比較的物件2
	 * @return 屬性差異比較結果boolean
	 */
	public static boolean compareObject(Object oldObject, Object newObject) {
		Map<String, Map<String,Object>> resultMap=compareFields(oldObject,newObject);
		
		if(resultMap.size()>0) {
			return true;
		}else {
			return false;
		}
	}
	
	/**
	 * 比較兩個實體屬性值，返回一個map以有差異的屬性名為key，value為一個Map分別存oldObject,newObject此屬性名的值
	 * @param oldObject 進行屬性比較的物件1
	 * @param newObject 進行屬性比較的物件2
	 * @return 屬性差異比較結果map
	 */
	@SuppressWarnings("rawtypes")
	public static Map<String, Map<String,Object>> compareFields(Object oldObject, Object newObject) {
		Map<String, Map<String, Object>> map = null;
		
		try{	
			/**
			 * 只有兩個物件都是同一型別的才有可比性
			 */
			if (oldObject.getClass() == newObject.getClass()) {
				map = new HashMap<String, Map<String,Object>>();
				
				Class clazz = oldObject.getClass();
				//獲取object的所有屬性
				PropertyDescriptor[] pds = Introspector.getBeanInfo(clazz,Object.class).getPropertyDescriptors();
				
				for (PropertyDescriptor pd : pds) {
					//遍歷獲取屬性名
					String name = pd.getName();
					
					//獲取屬性的get方法
					Method readMethod = pd.getReadMethod();
					
					// 在oldObject上呼叫get方法等同於獲得oldObject的屬性值
					Object oldValue = readMethod.invoke(oldObject);
					// 在newObject上呼叫get方法等同於獲得newObject的屬性值
					Object newValue = readMethod.invoke(newObject);
					
					if(oldValue instanceof List){
						continue;
					}
					
					if(newValue instanceof List){
						continue;
					}
					
					if(oldValue instanceof Timestamp){
						oldValue = new Date(((Timestamp) oldValue).getTime());
					}
					
					if(newValue instanceof Timestamp){
						newValue = new Date(((Timestamp) newValue).getTime());
					}
					
					if(oldValue == null && newValue == null){
						continue;
					}else if(oldValue == null && newValue != null){
						Map<String,Object> valueMap = new HashMap<String,Object>();
							valueMap.put("oldValue",oldValue);
							valueMap.put("newValue",newValue);
						
						map.put(name, valueMap);
						
						continue;
					}
					
					if (!oldValue.equals(newValue)) {// 比較這兩個值是否相等,不等就可以放入map了
						Map<String,Object> valueMap = new HashMap<String,Object>();
							valueMap.put("oldValue",oldValue);
							valueMap.put("newValue",newValue);
						
						map.put(name, valueMap);
					}
				}
			}
		}catch(Exception e){
			e.printStackTrace();
		}
		
		return map;
	}

}

注意：本工具類不適用於比較包含List，Map等類的Class。