REST Assured 68 - Compare Two JSON Using Jackson – Java Library

API 测试，有时需要比较两个 JSON。例如：我们想每次从一个 API返回的结果是一样的，或部分 response body 结果是不变的，就可以直接比较已经存在的 JSON response，省去了写大量逻辑代码去断言。

有许多好的 Java 库可以用来比较，本文我们主要了解用 Jackson 库来比较两个 JSON response。

添加 jackson databind依赖

    com.fasterxml.jackson.core
    jackson-databind
    2.12.1

Jackson API 提供一个抽象类 JsonNode， JsonNode 有一个抽象方法 equals() 可以用来比较 node objects。node objects 的相等是指 node 的整表层级结点都相等。equals() 抽象方法是被 ObjectNode 和 ArrayNode 类实现的。

我们首先需要将给定的 JSON 转换成 JsonNode (或 ObjectNode 或 ArrayNode)，然后调用 equals() 即可。

注意点：如果 JSON nodes 相等，那么 equals() 方法将返回 true，但是 JSON nodes 里的节点顺序是不关心的。但是如果是 JSON Array，关心顺序，顺序不同将影响两个 JSON array 的相等。

比较 JSON Objects

import org.junit.Test;
 
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
 
public class CompareJsonObjects {
	
	String JsonObject1;
	String jsonObject2;
	ObjectMapper objectMapper;
	JsonNode jsonNode1;
	JsonNode jsonNode2;
	
	@Test
	public void compareTwoJsonObjects() throws JsonMappingException, JsonProcessingException
	{
		JsonObject1 = "{rn" + 
				"  "firstName" : "Amod",rn" + 
				"  "lastName" : "Mahajan"rn" + 
				"}";
		
		jsonObject2 = "{rn" + 
				"  "firstName" : "Amod",rn" + 
				"  "lastName" : "Mahajan"rn" + 
				"}";
		
		objectMapper = new ObjectMapper();
		jsonNode1 = objectMapper.readTree(JsonObject1);
		jsonNode2 = objectMapper.readTree(jsonObject2);
		
		// Checking if both json objects are same
		System.out.println(jsonNode1.equals(jsonNode2));
	}
	
	@Test
	public void compareTwoJsonObjectsWithDifferentOrderOfRootElements() throws JsonMappingException, JsonProcessingException
	{
		// Change in order of elements does not impact
		JsonObject1 = "{rn" + 
				"  "firstName" : "Amod",rn" + 
				"  "lastName" : "Mahajan"rn" + 
				"}";
		
		jsonObject2 = "{rn" + 
				"  "lastName" : "Mahajan",rn" + 
				"  "firstName" : "Amod"rn" + 
				"  rn" + 
				"}";
		
		jsonNode1 = objectMapper.readTree(JsonObject1);
		jsonNode2 = objectMapper.readTree(jsonObject2);
		
		System.out.println(jsonNode1.equals(jsonNode2));
	}
	
	@Test
	public void compareTwoNestedJsonObjects() throws JsonMappingException, JsonProcessingException
	{
		
		// Nested json objects can also be compared with equals method
		JsonObject1 = "{rn" + 
				"  "lastName": "Mahajan",rn" + 
				"  "firstName": "Amod",rn" + 
				"  "address": {rn" + 
				"    "city": "Katihar",rn" + 
				"    "state": "Bihar"rn" + 
				"  }rn" + 
				"}";
		jsonObject2 = "{rn" + 
				"  "lastName": "Mahajan",rn" + 
				"  "firstName": "Amod",rn" + 
				"  "address": {rn" + 
				"    "city": "Katihar",rn" + 
				"    "state": "Bihar"rn" + 
				"  }rn" + 
				"}";
		
		jsonNode1 = objectMapper.readTree(JsonObject1);
		jsonNode2 = objectMapper.readTree(jsonObject2);
		
		System.out.println(jsonNode1.equals(jsonNode2));
		
	}
 
}

结果：JSON Object 相等，顺序可以不同

true
true
true

比较 JSON Arrays

import org.junit.Test;
 
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
 
public class CompareJsonArrays {
	
	String jsonArray1;
	String jsonArray2;
	ObjectMapper objectMapper;
	JsonNode jsonNode1;
	JsonNode jsonNode2;
	
	@Test
	public void compareTwoJsonArrays() throws JsonMappingException, JsonProcessingException
	{
		jsonArray1 = "[rn" + 
				"  {rn" + 
				"    "lastName": "Mahajan",rn" + 
				"    "firstName": "Amod",rn" + 
				"    "address": {rn" + 
				"      "city": "Katihar",rn" + 
				"      "state": "Bihar"rn" + 
				"    }rn" + 
				"  },rn" + 
				"  {rn" + 
				"    "lastName": "Animesh",rn" + 
				"    "firstName": "Prashant",rn" + 
				"    "address": {rn" + 
				"      "city": "Kolkata",rn" + 
				"      "state": "WB"rn" + 
				"    }rn" + 
				"  }rn" + 
				"]";
		
		jsonArray2 = "[rn" + 
				"  {rn" + 
				"    "lastName": "Mahajan",rn" + 
				"    "firstName": "Amod",rn" + 
				"    "address": {rn" + 
				"      "city": "Katihar",rn" + 
				"      "state": "Bihar"rn" + 
				"    }rn" + 
				"  },rn" + 
				"  {rn" + 
				"    "lastName": "Animesh",rn" + 
				"    "firstName": "Prashant",rn" + 
				"    "address": {rn" + 
				"      "city": "Kolkata",rn" + 
				"      "state": "WB"rn" + 
				"    }rn" + 
				"  }rn" + 
				"]";
		
		objectMapper = new ObjectMapper();
		jsonNode1 = objectMapper.readTree(jsonArray1);
		jsonNode2 = objectMapper.readTree(jsonArray2);
		
		// Checking if both json objects are same
		System.out.println(jsonNode1.equals(jsonNode2));
	}
	
	@Test
	public void compareTwoJsonArraysWithDifferentOrderOfElements() throws JsonMappingException, JsonProcessingException
	{
		
		// Change in order of elements in array will impact and it will not be considered same
		jsonArray1 = "[rn" + 
				"  {rn" + 
				"    "lastName": "Mahajan",rn" + 
				"    "firstName": "Amod",rn" + 
				"    "address": {rn" + 
				"      "city": "Katihar",rn" + 
				"      "state": "Bihar"rn" + 
				"    }rn" + 
				"  },rn" + 
				"  {rn" + 
				"    "lastName": "Animesh",rn" + 
				"    "firstName": "Prashant",rn" + 
				"    "address": {rn" + 
				"      "city": "Kolkata",rn" + 
				"      "state": "WB"rn" + 
				"    }rn" + 
				"  }rn" + 
				"]";
		
		jsonArray2 = "[rn" + 
				"  {rn" + 
				"    "lastName": "Animesh",rn" + 
				"    "firstName": "Prashant",rn" + 
				"    "address": {rn" + 
				"      "city": "Kolkata",rn" + 
				"      "state": "WB"rn" + 
				"    }rn" + 
				"  },rn" + 
				"  {rn" + 
				"    "lastName": "Mahajan",rn" + 
				"    "firstName": "Amod",rn" + 
				"    "address": {rn" + 
				"      "city": "Katihar",rn" + 
				"      "state": "Bihar"rn" + 
				"    }rn" + 
				"  }rn" + 
				"]";
		
		jsonNode1 = objectMapper.readTree(jsonArray1);
		jsonNode2 = objectMapper.readTree(jsonArray2);
		
		System.out.println(jsonNode1.equals(jsonNode2));
		
		
	}
 
}

结果：JSON Array中顺序不同，也是不相等。

true
false