jackson json to Object parsing

Question

I have a task to parse Json to Java Class.

Json fragment I am trying to parse and have problems with is something like tree structure.

The key point here is that parameterValue may be string, or another array of parameter name/value pairs;

I would like to use Jackson mapper

Response response = mapper.readValue(jsonObjstring, Response.class);

The problem here is that I do not know how can I describe Response class here, so it could be auto parsed by Jackson. If it is even possible.

Json:

[{
  "parameterName" : "name",
  "parameterValue" : "value"
}, {
  "parameterName" : "apnRecord",
  "parameterValue" : [{
     "parameterName" : "name",
     "parameterValue" : "value"
  }, {
     "parameterName" : "name",
     "parameterValue" : "value"
  }, {
     "parameterName" : "name",
     "parameterValue" : "value"
  }, {
     "parameterName" : "name",
     "parameterValue" : "value"
  }, {
     "parameterName" : "name",
     "parameterValue" : "value"
  }, {
     "parameterName" : "name",
     "parameterValue" : "value"
  }]
}]

Answer 1

You can try this online json to java pojo mapper, It produces the required result and it comes in handy for me many times.

http://pojo.sodhanalibrary.com/

Try it and if you face any more difficulties provide the complete json you receive, we can work out some thing else.

Answer 2

Create a POJO Response.java class which contains your fields, and getters/setters, create a standard constructor and one which contains your fields, and a toString method(). I show you an example with Annotations

define class like:

@JsonAutoDetect
@JsonSerialize
public class Response implements Serializable

then your fields with

@JsonProperty
private String parameterName;

and lastly your constructors fe like this

@JsonCreator
public Response(@JsonProperty("parameterName") String parameterName) {
    this.parameterName = parameterName;
}

Answer 3

I have defined it as

private List<List<Object>> resultParameters;

then jackson maper parses it (Object) to LinkedHashMapEnty when it is final value or to ArrayList - if it is not a value but another List of values;

It can be closed;

Answer 4

package test;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Test {

    public static void main(String[] args) {

        String readJsonAsString = "[{\r\n  \"parameterName\" : \"name\",\r\n  \"parameterValue\" : \"value\"\r\n}, {\r\n  \"parameterName\" : \"apnRecord\",\r\n  \"parameterValue\" : [{\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }, {\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }, {\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }, {\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }, {\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }, {\r\n     \"parameterName\" : \"name\",\r\n     \"parameterValue\" : \"value\"\r\n  }]\r\n}]";

        try {

            ObjectMapper mapper = new ObjectMapper();
            JsonNode jsonNodes = mapper.readTree(readJsonAsString.toString());
            for (JsonNode jsonNode : jsonNodes) {
                System.out.println(jsonNode.get("parameterName"));
            }


        } catch (JsonProcessingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

1st need to convert json to string format, then by ObjectMapper need to convert it into tree structure.

for this you need to use 3 jars : jackson-annotations-2.3.5.jar jackson-core-2.3.5.jar jackson-databind-2.3.5.jar