Convert JSON to Map

Question

What is the best way to convert a JSON code as this           data                     field1     value1             field2     value2            in a Java Map in which one the keys are  field1  field2  and the values for those fields are  value1  value2    Any ideas  Should I use Json-lib for that  Or better if I write my own parser

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If you re using org json  JSONObject has a method toMap    You can easily do   Map lt String  Object gt  myMap   myJsonObject toMap

User · Answer

Use JSON lib E g  http   www json org java      Assume you have a Map lt String  String gt  in JSONObject jdata  SuppressWarnings  unchecked   Iterator lt String gt  nameItr   jdata keys    Map lt String  String gt  outMap   new HashMap lt String  String gt     while nameItr hasNext          String name   nameItr next        outMap put name  jdata getString name

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java lang reflect Type mapType   new TypeToken lt Map lt String  Object gt  gt      getType    Gson gson   new Gson    Map lt String  Object gt  categoryicons   gson fromJson json  mapType

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Try this code    public static Map lt String  Object gt  convertJsonIntoMap String jsonFile            Map lt String  Object gt  map   new HashMap lt  gt             try               ObjectMapper mapper   new ObjectMapper                mapper configure DeserializationFeature UNWRAP ROOT VALUE  true               mapper readValue jsonFile  new TypeReference lt Map lt String  Object gt  gt                                  map   mapper readValue jsonFile  new TypeReference lt Map lt String  String gt  gt                                catch  IOException e                e printStackTrace                      return map

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java lang reflect Type mapType   new TypeToken lt Map lt String  Object gt  gt      getType    Gson gson   new Gson    Map lt String  Object gt  categoryicons   gson fromJson json  mapType

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I hope you were joking about writing your own parser   -  For such a simple mapping  most tools from http   json org  section java  would work  For one of them  Jackson https   github com FasterXML jackson-databind  5-minute-tutorial-streaming-parser-generator   you d do  Map lt String Object gt  result           new ObjectMapper   readValue JSON SOURCE  HashMap class     where JSON SOURCE is a File  input stream  reader  or json content String

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Using the GSON library    import com google gson Gson  import com google common reflect TypeToken  import java lang reclect Type    Use the following code   Type mapType   new TypeToken lt Map lt String  Map gt  gt      getType      Map lt String  String   gt  son   new Gson   fromJson easyString  mapType

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I do it this way  It s Simple   import java util Map  import org json JSONObject  import com google gson Gson   public class Main       public static void main String   args            JSONObject jsonObj   new JSONObject      f1     v1                SuppressWarnings  unchecked           Map lt String  String gt  map   new Gson   fromJson jsonObj toString   Map class           System out println map

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This way its works like a Map     JSONObject fieldsJson   new JSONObject json   String value   fieldsJson getString key     lt dependency gt       lt groupId gt org codehaus jettison lt  groupId gt       lt artifactId gt jettison lt  artifactId gt       lt version gt 1 1 lt  version gt   lt  dependency gt

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The JsonTools library is very complete  It can be found at Github

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Using the GSON library    import com google gson Gson  import com google common reflect TypeToken  import java lang reclect Type    Use the following code   Type mapType   new TypeToken lt Map lt String  Map gt  gt      getType      Map lt String  String   gt  son   new Gson   fromJson easyString  mapType

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Underscore-java library can convert json string to hash map  I am the maintainer of the project   Code example   import com github underscore lodash U  import java util     public class Main         SuppressWarnings  unchecked       public static void main String   args            String json                            data                                                     field1       value1                              field2       value2                                                     Map lt String  Object gt  data    Map  U get  Map lt String  Object gt   U fromJson json    data           System out println data               field1 value1  field2 value2

User · Answer

The JsonTools library is very complete  It can be found at Github

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With google s Gson 2 7  probably earlier versions too  but I tested 2 7  it s as simple as   Map map   gson fromJson json  Map class     Which returns a Map of type class com google gson internal LinkedTreeMap and works recursively on nested objects

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This way its works like a Map     JSONObject fieldsJson   new JSONObject json   String value   fieldsJson getString key     lt dependency gt       lt groupId gt org codehaus jettison lt  groupId gt       lt artifactId gt jettison lt  artifactId gt       lt version gt 1 1 lt  version gt   lt  dependency gt

User · Answer

I do it this way  It s Simple   import java util Map  import org json JSONObject  import com google gson Gson   public class Main       public static void main String   args            JSONObject jsonObj   new JSONObject      f1     v1                SuppressWarnings  unchecked           Map lt String  String gt  map   new Gson   fromJson jsonObj toString   Map class           System out println map

User · Answer

JSON to Map always gonna be a string object data type  i haved GSON lib from google   works very well and JDK 1 5 is  the min requirement

User · Answer

Try this code    public static Map lt String  Object gt  convertJsonIntoMap String jsonFile            Map lt String  Object gt  map   new HashMap lt  gt             try               ObjectMapper mapper   new ObjectMapper                mapper configure DeserializationFeature UNWRAP ROOT VALUE  true               mapper readValue jsonFile  new TypeReference lt Map lt String  Object gt  gt                                  map   mapper readValue jsonFile  new TypeReference lt Map lt String  String gt  gt                                catch  IOException e                e printStackTrace                      return map

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My post could be helpful for others  so imagine you have a map with a specific object in values  something like that           shopping list             996386                id  996386            label   My 1st shopping list             current  true            nb reference  6                 888540                id  888540            label   My 2nd shopping list             current  false            nb reference  2                  To parse this JSON file with GSON library  it s easy   if your project is mavenized   lt dependency gt       lt groupId gt com google code gson lt  groupId gt       lt artifactId gt gson lt  artifactId gt       lt version gt 2 3 1 lt  version gt   lt  dependency gt    Then use this snippet    import com google gson Gson  import com google gson JsonElement  import com google gson JsonObject  import com google gson JsonParser     Read the JSON file JsonElement root   new JsonParser   parse new FileReader   path to the json file in your file system json        Get the content of the first map JsonObject object   root getAsJsonObject   get  shopping list   getAsJsonObject       Iterate over this map Gson gson   new Gson    for  Entry lt String  JsonElement gt  entry   object entrySet          ShoppingList shoppingList   gson fromJson entry getValue    ShoppingList class       System out println shoppingList getLabel         The corresponding POJO should be something like that    public class ShoppingList        int id       String label       boolean current       int nb reference         Setters  amp  Getters           Hope it helps

User · Answer

If you re using org json  JSONObject has a method toMap    You can easily do   Map lt String  Object gt  myMap   myJsonObject toMap

User · Answer

My post could be helpful for others  so imagine you have a map with a specific object in values  something like that           shopping list             996386                id  996386            label   My 1st shopping list             current  true            nb reference  6                 888540                id  888540            label   My 2nd shopping list             current  false            nb reference  2                  To parse this JSON file with GSON library  it s easy   if your project is mavenized   lt dependency gt       lt groupId gt com google code gson lt  groupId gt       lt artifactId gt gson lt  artifactId gt       lt version gt 2 3 1 lt  version gt   lt  dependency gt    Then use this snippet    import com google gson Gson  import com google gson JsonElement  import com google gson JsonObject  import com google gson JsonParser     Read the JSON file JsonElement root   new JsonParser   parse new FileReader   path to the json file in your file system json        Get the content of the first map JsonObject object   root getAsJsonObject   get  shopping list   getAsJsonObject       Iterate over this map Gson gson   new Gson    for  Entry lt String  JsonElement gt  entry   object entrySet          ShoppingList shoppingList   gson fromJson entry getValue    ShoppingList class       System out println shoppingList getLabel         The corresponding POJO should be something like that    public class ShoppingList        int id       String label       boolean current       int nb reference         Setters  amp  Getters           Hope it helps

User · Answer

I like google gson library  When you don t know structure of json  You can use  JsonElement root   new JsonParser   parse jsonString     and then you can work with json  e g  how to get  value1  from your gson   String value1   root getAsJsonObject   get  data   getAsJsonObject   get  field1   getAsString

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JSON to Map always gonna be a string object data type  i haved GSON lib from google   works very well and JDK 1 5 is  the min requirement

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If you need pure Java without any dependencies  you can use build in Nashorn API from Java 8  It is deprecated in Java 11   This is working for me       import javax script ScriptEngine  import javax script ScriptEngineManager  import javax script ScriptException       public class JsonUtils        public static Map parseJSON String json  throws ScriptException           ScriptEngineManager sem   new ScriptEngineManager            ScriptEngine engine   sem getEngineByName  javascript             String script    Java asJSONCompatible     json                 Object result   engine eval script            return  Map  result            Sample usage  JSON          data              id  1  username   bruce              id  2  username   clark              id  3  username   diana             Code       import jdk nashorn internal runtime JSONListAdapter       public static List lt String gt  getUsernamesFromJson Map json        List lt String gt  result   new LinkedList lt  gt          JSONListAdapter data    JSONListAdapter  json get  data         for Object obj   data            Map map    Map  obj          result add  String  map get  username                return result

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If you need pure Java without any dependencies  you can use build in Nashorn API from Java 8  It is deprecated in Java 11   This is working for me       import javax script ScriptEngine  import javax script ScriptEngineManager  import javax script ScriptException       public class JsonUtils        public static Map parseJSON String json  throws ScriptException           ScriptEngineManager sem   new ScriptEngineManager            ScriptEngine engine   sem getEngineByName  javascript             String script    Java asJSONCompatible     json                 Object result   engine eval script            return  Map  result            Sample usage  JSON          data              id  1  username   bruce              id  2  username   clark              id  3  username   diana             Code       import jdk nashorn internal runtime JSONListAdapter       public static List lt String gt  getUsernamesFromJson Map json        List lt String gt  result   new LinkedList lt  gt          JSONListAdapter data    JSONListAdapter  json get  data         for Object obj   data            Map map    Map  obj          result add  String  map get  username                return result

User · Answer

One more alternative is json-simple which can be found in Maven Central    JSONObject JSONValue parse someString     JSONObject is actually a Map    The artifact is 24kbytes  doesn t have other runtime dependencies

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One more alternative is json-simple which can be found in Maven Central    JSONObject JSONValue parse someString     JSONObject is actually a Map    The artifact is 24kbytes  doesn t have other runtime dependencies

User · Answer

Use JSON lib E g  http   www json org java      Assume you have a Map lt String  String gt  in JSONObject jdata  SuppressWarnings  unchecked   Iterator lt String gt  nameItr   jdata keys    Map lt String  String gt  outMap   new HashMap lt String  String gt     while nameItr hasNext          String name   nameItr next        outMap put name  jdata getString name

User · Answer

With google s Gson 2 7  probably earlier versions too  but I tested 2 7  it s as simple as   Map map   gson fromJson json  Map class     Which returns a Map of type class com google gson internal LinkedTreeMap and works recursively on nested objects

User · Answer

I hope you were joking about writing your own parser   -  For such a simple mapping  most tools from http   json org  section java  would work  For one of them  Jackson https   github com FasterXML jackson-databind  5-minute-tutorial-streaming-parser-generator   you d do  Map lt String Object gt  result           new ObjectMapper   readValue JSON SOURCE  HashMap class     where JSON SOURCE is a File  input stream  reader  or json content String

User · Answer

import net sf json JSONObject  JSONObject fromObject yourJsonString  toMap

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import net sf json JSONObject  JSONObject fromObject yourJsonString  toMap

User · Answer

I like google gson library  When you don t know structure of json  You can use  JsonElement root   new JsonParser   parse jsonString     and then you can work with json  e g  how to get  value1  from your gson   String value1   root getAsJsonObject   get  data   getAsJsonObject   get  field1   getAsString

User · Answer

Underscore-java library can convert json string to hash map  I am the maintainer of the project   Code example   import com github underscore lodash U  import java util     public class Main         SuppressWarnings  unchecked       public static void main String   args            String json                            data                                                     field1       value1                              field2       value2                                                     Map lt String  Object gt  data    Map  U get  Map lt String  Object gt   U fromJson json    data           System out println data               field1 value1  field2 value2

[java] Convert JSON to Map

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