Testing two JSON objects for equality ignoring child order in Java

Question

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

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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    Source code Home page  Javadocs for main matcher     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

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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

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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

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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 lt String gt  l1    Arrays asList JSONObject getNames js1        Collections sort l1       List lt String gt  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

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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

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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  lt  obj1Array length    i                                  boolean matchFound   false                   for  int j   0  j  lt  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

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You can try JsonUnit  It can compare two JSON objects and report differences  It s built on top of Jackson  For example assertThatJson  quot    quot test  quot  1  quot   isEqualTo  quot   n  quot test  quot   2 n  quot     Results in java lang AssertionError  JSON documents are different  Different value found in node  quot test quot   Expected 1  got 2

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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  quot       quot    json2   new JSONObject  quot       quot    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

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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 lt String gt  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 lt JsonNode gt  remaining   new ArrayList lt  gt             expectJson forEach remaining  add              O N 2             for int i 0  i  lt  actualJson size      i                boolean oneEquals   false              for int j 0  j  lt  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

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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

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What I did is converting the jsons into maps using gson and comparing the maps using assertj  Map lt Object  Object gt  resMap   gson fromJson res  new TypeToken lt Map lt Object  Object gt  gt       getType     Map lt Object  Object gt  expectedMap   gson fromJson expected  new TypeToken lt Map lt Object  Object gt  gt       getType     Assertions assertThat resMap  usingRecursiveComparison   isEqualTo expectedMap    The result is a nice comparison between all attributes  recursively

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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

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I know it is usually considered only for testing but you could use the Hamcrest JSON comparitorSameJSONAs in Hamcrest JSON   Hamcrest JSON SameJSONAs

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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  quot Error comparing JSON objects   quot    e getMessage

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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

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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  amp  amp  json2    null                    Check whether both jsonElement are objects             if  json1 isJsonObject    amp  amp  json2 isJsonObject                      Set lt Entry lt String  JsonElement gt  gt  ens1     JsonObject  json1  entrySet                    Set lt Entry lt String  JsonElement gt  gt  ens2     JsonObject  json2  entrySet                    JsonObject json2obj    JsonObject  json2                  if  ens1    null  amp  amp  ens2    null                            ens2 size      ens1 size                           Iterate JSON Elements with Key values                     for  Entry lt String  JsonElement gt  en   ens1                            isEqual   isEqual  amp  amp  compareJson en getValue    json2obj get en getKey                                              else                       return false                                                  Check whether both jsonElement are arrays             else if  json1 isJsonArray    amp  amp  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  amp  amp  compareJson je  jarr2 get i                            i                                                                          Check whether both jsonElement are null             else if  json1 isJsonNull    amp  amp  json2 isJsonNull                      return true                                Check whether both jsonElement are primitives             else if  json1 isJsonPrimitive    amp  amp  json2 isJsonPrimitive                      if  json1 equals json2                         return true                    else                       return false                                  else                   return false                          else if  json1    null  amp  amp  json2    null                return true            else               return false                    return isEqual

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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  lt  qux  gt  but was  lt  xyzzy  gt

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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

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As a general architectural point  I usually advise against letting dependencies on a particular serialization format bleed out beyond your storage networking layer  thus  I d first recommend that you consider testing equality between your own application objects rather than their JSON manifestations   Having said that  I m currently a big fan of Jackson which my quick read of their ObjectNode equals   implementation suggests does the set membership comparison that you want   public boolean equals Object o        if  o    this  return true      if  o    null  return false      if  o getClass      getClass              return false            ObjectNode other    ObjectNode  o      if  other size      size              return false            if   children    null            for  Map Entry lt String  JsonNode gt  en    children entrySet                  String key   en getKey                JsonNode value   en getValue                 JsonNode otherValue   other get key                if  otherValue    null     otherValue equals value                     return false                                    return true

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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 lt HashMap lt String  Object gt  gt        mapper readValue actualJson  new TypeReference lt HashMap lt String  Object gt  gt           A similar approach can be used if the JSON object is an array instead

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Use this library  https   github com lukas-krecan JsonUnit Pom   lt dependency gt       lt groupId gt net javacrumbs json-unit lt  groupId gt       lt artifactId gt json-unit-assertj lt  artifactId gt       lt version gt 2 24 0 lt  version gt       lt scope gt test lt  scope gt   lt  dependency gt   IGNORING ARRAY ORDER - ignores order in arrays assertThatJson  quot    quot test  quot   1 2 3   quot      when Option IGNORING ARRAY ORDER     isEqualTo  quot    quot test  quot    3 2 1   quot

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JSON areEqual json1  json2     using BlobCity Java Commons   https   tech blobcity com 2018 09 02 json-equals-in-java-to-compare-two-jsons

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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 lt String gt  keys   obj keys                Map lt String  Object gt  jsonMap   new HashMap lt  gt                 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 lt Object gt  jsonSet   new HashSet lt  gt                 for  int i   0  i  lt  arr length    i                      jsonSet add convertJsonElement arr get i                               return jsonSet            else               return elem

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Looking at the answers  I tried JSONAssert but it failed  So I used Jackson with zjsonpatch  I posted details in the SO answer here

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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

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Try Skyscreamer s JSONAssert   Its non-strict mode has two major advantages that make it less brittle    Object extensibility  e g  With an expected value of  id 1   this would still pass   id 1 moredata  x     Loose array ordering  e g    dog   cat      cat   dog      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

[java] Testing two JSON objects for equality ignoring child order in Java

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