I'm looking for a JSON parsing library that supports comparing two JSON objects ignoring child order, specifically for unit testing JSON returning from a web service.
Do any of the major JSON libraries support this? The org.json library simply does a reference comparison.
Using GSON
JsonParser parser = new JsonParser();
JsonElement o1 = parser.parse("{a : {a : 2}, b : 2}");
JsonElement o2 = parser.parse("{b : 2, a : {a : 2}}");
assertEquals(o1, o2);
Edit: Since GSON v2.8.6 the instance method JsonParser.parse is deprecated. You have to use the static method JsonParser.parseString:
JsonElement o1 = JsonParser.parseString("{a : {a : 2}, b : 2}");
JsonElement o2 = JsonParser.parseString("{b : 2, a : {a : 2}}");
assertEquals(o1, o2);
Nothing else seemed to work quite right, so I wrote this:
private boolean jsonEquals(JsonNode actualJson, JsonNode expectJson) {
if(actualJson.getNodeType() != expectJson.getNodeType()) return false;
switch(expectJson.getNodeType()) {
case NUMBER:
return actualJson.asDouble() == expectJson.asDouble();
case STRING:
case BOOLEAN:
return actualJson.asText().equals(expectJson.asText());
case OBJECT:
if(actualJson.size() != expectJson.size()) return false;
Iterator<String> fieldIterator = actualJson.fieldNames();
while(fieldIterator.hasNext()) {
String fieldName = fieldIterator.next();
if(!jsonEquals(actualJson.get(fieldName), expectJson.get(fieldName))) {
return false;
}
}
break;
case ARRAY:
if(actualJson.size() != expectJson.size()) return false;
List<JsonNode> remaining = new ArrayList<>();
expectJson.forEach(remaining::add);
// O(N^2)
for(int i=0; i < actualJson.size(); ++i) {
boolean oneEquals = false;
for(int j=0; j < remaining.size(); ++j) {
if(jsonEquals(actualJson.get(i), remaining.get(j))) {
oneEquals = true;
remaining.remove(j);
break;
}
}
if(!oneEquals) return false;
}
break;
default:
throw new IllegalStateException();
}
return true;
}
I'm using this, and works fine for me (with org.json.*):
package com.project1.helpers;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class JSONUtils {
public static boolean areEqual(Object ob1, Object ob2) throws JSONException {
Object obj1Converted = convertJsonElement(ob1);
Object obj2Converted = convertJsonElement(ob2);
return obj1Converted.equals(obj2Converted);
}
private static Object convertJsonElement(Object elem) throws JSONException {
if (elem instanceof JSONObject) {
JSONObject obj = (JSONObject) elem;
Iterator<String> keys = obj.keys();
Map<String, Object> jsonMap = new HashMap<>();
while (keys.hasNext()) {
String key = keys.next();
jsonMap.put(key, convertJsonElement(obj.get(key)));
}
return jsonMap;
} else if (elem instanceof JSONArray) {
JSONArray arr = (JSONArray) elem;
Set<Object> jsonSet = new HashSet<>();
for (int i = 0; i < arr.length(); i++) {
jsonSet.add(convertJsonElement(arr.get(i)));
}
return jsonSet;
} else {
return elem;
}
}
}
One thing I did and it works wonders is to read both objects into HashMap and then compare with a regular assertEquals(). It will call the equals() method of the hashmaps, which will recursively compare all objects inside (they will be either other hashmaps or some single value object like a string or integer). This was done using Codehaus' Jackson JSON parser.
assertEquals(mapper.readValue(expectedJson, new TypeReference<HashMap<String, Object>>(){}), mapper.readValue(actualJson, new TypeReference<HashMap<String, Object>>(){}));
A similar approach can be used if the JSON object is an array instead.
For those like me wanting to do this with Jackson, you can use json-unit.
JsonAssert.assertJsonEquals(jsonNode1, jsonNode2);
The errors give useful feedback on the type of mismatch:
java.lang.AssertionError: JSON documents have different values:
Different value found in node "heading.content[0].tag[0]". Expected 10209, got 10206.
You could try using json-lib's JSONAssert class:
JSONAssert.assertEquals(
"{foo: 'bar', baz: 'qux'}",
JSONObject.fromObject("{foo: 'bar', baz: 'xyzzy'}")
);
Gives:
junit.framework.ComparisonFailure: objects differed at key [baz]; expected:<[qux]> but was:<[xyzzy]>
You can try JsonUnit. It can compare two JSON objects and report differences. It's built on top of Jackson.
For example
assertThatJson("{\"test\":1}").isEqualTo("{\n\"test\": 2\n}");
Results in
java.lang.AssertionError: JSON documents are different:
Different value found in node "test". Expected 1, got 2.
If you are already using JUnit, the latest version now employs Hamcrest. It is a generic matching framework (especially useful for unit testing) that can be extended to build new matchers.
There is a small open source library called hamcrest-json with JSON-aware matches. It is well documented, tested, and supported. Below are some useful links:
Example code using objects from the JSON library org.json.simple:
Assert.assertThat(
jsonObject1.toJSONString(),
SameJSONAs.sameJSONAs(jsonObject2.toJSONString()));
Optionally, you may (1) allow "any-order" arrays and (2) ignore extra fields.
Since there are a variety of JSON libraries for Java (Jackson, GSON, json-lib, etc.), it is useful that hamcrest-json supports JSON text (as java.lang.String), as well as natively supporting objects from Douglas Crockford's JSON library org.json.
Finally, if you are not using JUnit, you can use Hamcrest directly for assertions. (I wrote about it here.)
Karate is exactly what you are looking for. Here is an example:
* def myJson = { foo: 'world', hey: 'ho', zee: [5], cat: { name: 'Billie' } }
* match myJson = { cat: { name: 'Billie' }, hey: 'ho', foo: 'world', zee: [5] }
(disclaimer: dev here)
For org.json I've rolled out my own solution, a method that compares to JSONObject instances. I didn't work with complex JSON objects in that project, so I don't know whether this works in all scenarios. Also, given that I use this in unit tests, I didn't put effort into optimizations. Here it is:
public static boolean jsonObjsAreEqual (JSONObject js1, JSONObject js2) throws JSONException {
if (js1 == null || js2 == null) {
return (js1 == js2);
}
List<String> l1 = Arrays.asList(JSONObject.getNames(js1));
Collections.sort(l1);
List<String> l2 = Arrays.asList(JSONObject.getNames(js2));
Collections.sort(l2);
if (!l1.equals(l2)) {
return false;
}
for (String key : l1) {
Object val1 = js1.get(key);
Object val2 = js2.get(key);
if (val1 instanceof JSONObject) {
if (!(val2 instanceof JSONObject)) {
return false;
}
if (!jsonObjsAreEqual((JSONObject)val1, (JSONObject)val2)) {
return false;
}
}
if (val1 == null) {
if (val2 != null) {
return false;
}
} else if (!val1.equals(val2)) {
return false;
}
}
return true;
}
Use this library: https://github.com/lukas-krecan/JsonUnit
Pom:
<dependency>
<groupId>net.javacrumbs.json-unit</groupId>
<artifactId>json-unit-assertj</artifactId>
<version>2.24.0</version>
<scope>test</scope>
</dependency>
IGNORING_ARRAY_ORDER - ignores order in arrays
assertThatJson("{\"test\":[1,2,3]}")
.when(Option.IGNORING_ARRAY_ORDER)
.isEqualTo("{\"test\": [3,2,1]}");
What I did is converting the jsons into maps using gson and comparing the maps using assertj:
Map<Object, Object> resMap = gson.fromJson(res, new TypeToken<Map<Object, Object>>() {}.getType());
Map<Object, Object> expectedMap = gson.fromJson(expected, new TypeToken<Map<Object, Object>>() {}.getType());
Assertions.assertThat(resMap).usingRecursiveComparison().isEqualTo(expectedMap);
The result is a nice comparison between all attributes, recursively!!!
JSON.areEqual(json1, json2); //using BlobCity Java Commons
https://tech.blobcity.com/2018/09/02/json-equals-in-java-to-compare-two-jsons
Here is the code using Jackson ObjectMapper. To know more read this article.
import com.fasterxml.jackson.*
boolean compareJsonPojo(Object pojo1, Object pojo2) {
try {
ObjectMapper mapper = new ObjectMapper();
String str1 = mapper.writeValueAsString(pojo1);
String str2 = mapper.writeValueAsString(pojo2);
return mapper.readTree(str1).equals(mapper.readTree(str2));
} catch (JsonProcessingException e) {
throw new AssertionError("Error comparing JSON objects: " + e.getMessage());
}
}
I know it is usually considered only for testing but you could use the Hamcrest JSON comparitorSameJSONAs in Hamcrest JSON.
You can use zjsonpatch library, which presents the diff information in accordance with RFC 6902 (JSON Patch). Its very easy to use. Please visit its description page for its usage
Following code will be more helpful to compare two JsonObject, JsonArray, JsonPrimitive and JasonElements.
private boolean compareJson(JsonElement json1, JsonElement json2) {
boolean isEqual = true;
// Check whether both jsonElement are not null
if (json1 != null && json2 != null) {
// Check whether both jsonElement are objects
if (json1.isJsonObject() && json2.isJsonObject()) {
Set<Entry<String, JsonElement>> ens1 = ((JsonObject) json1).entrySet();
Set<Entry<String, JsonElement>> ens2 = ((JsonObject) json2).entrySet();
JsonObject json2obj = (JsonObject) json2;
if (ens1 != null && ens2 != null) {
// (ens2.size() == ens1.size())
// Iterate JSON Elements with Key values
for (Entry<String, JsonElement> en : ens1) {
isEqual = isEqual && compareJson(en.getValue(), json2obj.get(en.getKey()));
}
} else {
return false;
}
}
// Check whether both jsonElement are arrays
else if (json1.isJsonArray() && json2.isJsonArray()) {
JsonArray jarr1 = json1.getAsJsonArray();
JsonArray jarr2 = json2.getAsJsonArray();
if (jarr1.size() != jarr2.size()) {
return false;
} else {
int i = 0;
// Iterate JSON Array to JSON Elements
for (JsonElement je : jarr1) {
isEqual = isEqual && compareJson(je, jarr2.get(i));
i++;
}
}
}
// Check whether both jsonElement are null
else if (json1.isJsonNull() && json2.isJsonNull()) {
return true;
}
// Check whether both jsonElement are primitives
else if (json1.isJsonPrimitive() && json2.isJsonPrimitive()) {
if (json1.equals(json2)) {
return true;
} else {
return false;
}
} else {
return false;
}
} else if (json1 == null && json2 == null) {
return true;
} else {
return false;
}
return isEqual;
}
Looking at the answers, I tried JSONAssert but it failed. So I used Jackson with zjsonpatch. I posted details in the SO answer here.
Try this:
public static boolean jsonsEqual(Object obj1, Object obj2) throws JSONException
{
if (!obj1.getClass().equals(obj2.getClass()))
{
return false;
}
if (obj1 instanceof JSONObject)
{
JSONObject jsonObj1 = (JSONObject) obj1;
JSONObject jsonObj2 = (JSONObject) obj2;
String[] names = JSONObject.getNames(jsonObj1);
String[] names2 = JSONObject.getNames(jsonObj1);
if (names.length != names2.length)
{
return false;
}
for (String fieldName:names)
{
Object obj1FieldValue = jsonObj1.get(fieldName);
Object obj2FieldValue = jsonObj2.get(fieldName);
if (!jsonsEqual(obj1FieldValue, obj2FieldValue))
{
return false;
}
}
}
else if (obj1 instanceof JSONArray)
{
JSONArray obj1Array = (JSONArray) obj1;
JSONArray obj2Array = (JSONArray) obj2;
if (obj1Array.length() != obj2Array.length())
{
return false;
}
for (int i = 0; i < obj1Array.length(); i++)
{
boolean matchFound = false;
for (int j = 0; j < obj2Array.length(); j++)
{
if (jsonsEqual(obj1Array.get(i), obj2Array.get(j)))
{
matchFound = true;
break;
}
}
if (!matchFound)
{
return false;
}
}
}
else
{
if (!obj1.equals(obj2))
{
return false;
}
}
return true;
}
toMap() in JSONObject works fine with nested objects and arrays already.
As the java.util.Map interface specifies to check the mappings and not the order, comparing the Maps is fine and also recursive.
json1 = new JSONObject("{...}");
json2 = new JSONObject("{...}");
json1.toMap().equals(json2.toMap());
It will work fine with any order and nested elements.
It will NOT however work with extra/ignored elements. If those are known you can remove them before calling equals on the maps.
Do any of the major JSON libraries support this? The org.json library simply does a reference comparison.
But org.json does support this! Use similar() instead of equals().
For comparing jsons I recommend using JSONCompare: https://github.com/fslev/json-compare
// Compare by regex
String expected = "{\"a\":\".*me.*\"}";
String actual = "{\"a\":\"some text\"}";
JSONCompare.assertEquals(expected, actual); // True
// Check expected array has no extra elements
String expected = "[1,\"test\",4,\"!.*\"]";
String actual = "[4,1,\"test\"]";
JSONCompare.assertEquals(expected, actual); // True
// Check expected array has no numbers
String expected = "[\"\\\\\\d+\"]";
String actual = "[\"text\",\"test\"]";
JSONCompare.assertEquals(expected, actual); // True
// Check expected array has no numbers
String expected = "[\"\\\\\\d+\"]";
String actual = "[2018]";
JSONCompare.assertNotEquals(expected, actual); // True
I would do the following,
JSONObject obj1 = /*json*/;
JSONObject obj2 = /*json*/;
ObjectMapper mapper = new ObjectMapper();
JsonNode tree1 = mapper.readTree(obj1.toString());
JsonNode tree2 = mapper.readTree(obj2.toString());
return tree1.equals(tree2);
I'd take the library at http://json.org/java/, and modify the equals method of JSONObject and JSONArray to do a deep equality test. To make sure that it works regradless of the order of the children, all you need to do is replace the inner map with a TreeMap, or use something like Collections.sort().
Try Skyscreamer's JSONAssert.
Its non-strict mode has two major advantages that make it less brittle:
In strict mode it behaves more like json-lib's test class.
A test looks something like this:
@Test
public void testGetFriends() {
JSONObject data = getRESTData("/friends/367.json");
String expected = "{friends:[{id:123,name:\"Corby Page\"}"
+ ",{id:456,name:\"Solomon Duskis\"}]}";
JSONAssert.assertEquals(expected, data, false);
}
The parameters in the JSONAssert.assertEquals() call are expectedJSONString, actualDataString, and isStrict.
The result messages are pretty clear, which is important when comparing really big JSON objects.
Source: Stackoverflow.com