How to convert the following json string to java object?

Question

I want to convert the following JSON string to a java object:

String jsonString = "{
  "libraryname": "My Library",
  "mymusic": [
    {
      "Artist Name": "Aaron",
      "Song Name": "Beautiful"
    },
    {
      "Artist Name": "Britney",
      "Song Name": "Oops I did It Again"
    },
    {
      "Artist Name": "Britney",
      "Song Name": "Stronger"
    }
  ]
}"

My goal is to access it easily something like:

(e.g. MyJsonObject myobj = new MyJsonObject(jsonString)
myobj.mymusic[0].id would give me the ID, myobj.libraryname gives me "My Library").

I've heard of Jackson, but I am unsure how to use it to fit the json string I have since its not just key value pairs due to the "mymusic" list involved. How can I accomplish this with Jackson or is there some easier way I can accomplish this if Jackson is not the best for this?

Answer 1

No need to go with GSON for this; Jackson can do either plain Maps/Lists:

ObjectMapper mapper = new ObjectMapper();
Map<String,Object> map = mapper.readValue(json, Map.class);

or more convenient JSON Tree:

JsonNode rootNode = mapper.readTree(json);

By the way, there is no reason why you could not actually create Java classes and do it (IMO) more conveniently:

public class Library {
  @JsonProperty("libraryname")
  public String name;

  @JsonProperty("mymusic")
  public List<Song> songs;
}
public class Song {
  @JsonProperty("Artist Name") public String artistName;
  @JsonProperty("Song Name") public String songName;
}

Library lib = mapper.readValue(jsonString, Library.class);

Answer 2

Check out Google's Gson: http://code.google.com/p/google-gson/

From their website:

Gson gson = new Gson(); // Or use new GsonBuilder().create();
MyType target2 = gson.fromJson(json, MyType.class); // deserializes json into target2

You would just need to make a MyType class (renamed, of course) with all the fields in the json string. It might get a little more complicated when you're doing the arrays, if you prefer to do all of the parsing manually (also pretty easy) check out http://www.json.org/ and download the Java source for the Json parser objects.

Answer 3

Gson gson = new Gson();
JsonParser parser = new JsonParser();
JsonObject object = (JsonObject) parser.parse(response);// response will be the json String
YourPojo emp = gson.fromJson(object, YourPojo.class); 

Answer 4

Gson is also good for it: http://code.google.com/p/google-gson/

" Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of. "

Check the API examples:https://sites.google.com/site/gson/gson-user-guide#TOC-Overview More examples: http://www.mkyong.com/java/how-do-convert-java-object-to-from-json-format-gson-api/

Answer 5

Underscore-java can convert json to Object.

    String jsonString = "{\n" +
            "        \"libraryname\":\"My Library\",\n" +
            "                \"mymusic\":[{\"Artist Name\":\"Aaron\",\"Song Name\":\"Beautiful\"},\n" +
            "        {\"Artist Name\":\"Britney\",\"Song Name\":\"Oops I did It Again\"},\n" +
            "        {\"Artist Name\":\"Britney\",\"Song Name\":\"Stronger\"}]}";
    Map<String, Object> jsonObject = U.fromJsonMap(jsonString);
    System.out.println(jsonObject);

// {libraryname=My Library, mymusic=[{Artist Name=Aaron, Song Name=Beautiful}, {Artist Name=Britney, Song Name=Oops I did It Again}, {Artist Name=Britney, Song Name=Stronger}]}

    System.out.println(U.<String>get(jsonObject, "mymusic[0].Artist Name"));
// Aaron

Answer 6

Underscore-java ( which I am the developer of ) can convert json to Object.

import com.github.underscore.U;

    String jsonString = "{\n" +
            "        \"libraryname\":\"My Library\",\n" +
            "                \"mymusic\":[{\"Artist Name\":\"Aaron\",\"Song Name\":\"Beautiful\"},\n" +
            "        {\"Artist Name\":\"Britney\",\"Song Name\":\"Oops I did It Again\"},\n" +
            "        {\"Artist Name\":\"Britney\",\"Song Name\":\"Stronger\"}]}";
    Map<String, Object> jsonObject = U.fromJsonMap(jsonString);
    System.out.println(jsonObject);

    // {libraryname=My Library, mymusic=[{Artist Name=Aaron, Song Name=Beautiful}, {Artist Name=Britney, Song Name=Oops I did It Again}, {Artist Name=Britney, Song Name=Stronger}]}

    System.out.println(U.<String>get(jsonObject, "mymusic[0].Artist Name"));
    // Aaron

Answer 7

public void parseEmployeeObject() throws NoSuchFieldException, SecurityException, JsonParseException, JsonMappingException, IOException {

  Gson gson = new Gson();
  
  ObjectMapper mapper = new ObjectMapper();

    // convert JSON string to Book object
    Object obj = mapper.readValue(Paths.get("src/main/resources/file.json").toFile(), Object.class);
    
    
    endpoint = this.endpointUrl;        

    String jsonInString = new Gson().toJson(obj);

  JsonRootPojo organisation = gson.fromJson(jsonInString, JsonRootPojo.class);
  
  
  for(JsonFilter jfil  : organisation.getSchedule().getTradeQuery().getFilter())
  {
     String name = jfil.getName();
     String value = jfil.getValue();
  }
  
  System.out.println(organisation);
  

}

{ "schedule": { "cron": "30 19 2 MON-FRI", "timezone": "Europe/London",
"tradeQuery": { "filter": [ { "name": "bookType", "operand": "equals", "value": "FO" }, { "name": "bookType", "operand": "equals", "value": "FO" } ], "parameter": [ { "name": "format", "value": "CSV" }, { "name": "pagesize", "value": "1000" } ] }, "xslt":"" }

}

public class JesonSchedulePojo {

    public String cron;
    public String timezone;
    public JsonTradeQuery tradeQuery;
    public String xslt;
    
    
    public String getCron() {
        return cron;
    }
    public void setCron(String cron) {
        this.cron = cron;
    }
    public String getTimezone() {
        return timezone;
    }
    public void setTimezone(String timezone) {
        this.timezone = timezone;
    }

    public JsonTradeQuery getTradeQuery() {
        return tradeQuery;
    }
    public void setTradeQuery(JsonTradeQuery tradeQuery) {
        this.tradeQuery = tradeQuery;
    }
    public String getXslt() {
        return xslt;
    }
    public void setXslt(String xslt) {
        this.xslt = xslt;
    }
    @Override
    public String toString() {
        return "JesonSchedulePojo [cron=" + cron + ", timezone=" + timezone + ", tradeQuery=" + tradeQuery
                + ", xslt=" + xslt + "]";
    }
    
    

public class JsonTradeQuery {

 public ArrayList<JsonFilter> filter;
    public ArrayList<JsonParameter> parameter;
    public ArrayList<JsonFilter> getFilter() {
        return filter;
    }
    public void setFilter(ArrayList<JsonFilter> filter) {
        this.filter = filter;
    }
    public ArrayList<JsonParameter> getParameter() {
        return parameter;
    }
    public void setParameter(ArrayList<JsonParameter> parameter) {
        this.parameter = parameter;
    }
    @Override
    public String toString() {
        return "JsonTradeQuery [filter=" + filter + ", parameter=" + parameter + "]";
    }
    
    

public class JsonFilter {

public String name;
public String operand;
public String value;
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getOperand() {
    return operand;
}
public void setOperand(String operand) {
    this.operand = operand;
}
public String getValue() {
    return value;
}
public void setValue(String value) {
    this.value = value;
}
@Override
public String toString() {
    return "JsonFilter [name=" + name + ", operand=" + operand + ", value=" + value + "]";
}

public class JsonParameter {

public String name;
public String value;
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getValue() {
    return value;
}
public void setValue(String value) {
    this.value = value;
}
@Override
public String toString() {
    return "JsonParameter [name=" + name + ", value=" + value + "]";
}

public class JsonRootPojo {

public JesonSchedulePojo schedule;

public JesonSchedulePojo getSchedule() {
    return schedule;
}



public void setSchedule(JesonSchedulePojo schedule) {
    this.schedule = schedule;
}



@Override
public String toString() {
    return "JsonRootPojo [schedule=" + schedule + "]";
}



    
            

Answer 8

In my case, I passed the JSON string as a list. So use the below solution when you pass the list.

ObjectMapper mapper = new ObjectMapper();
String json = "[{\"classifier\":\"M\",\"results\":[{\"opened\":false}]}]";
List<Map<String, Object>>  map = mapper.readValue(json, new TypeReference<List<Map<String, Object>>>(){});