how to convert JSONArray to List of Object using camel-jackson

Question

Am having the String of json array as follow

{"Compemployes":[
    {
        "id":1001,
        "name":"jhon"
        },
        {
                "id":1002,
        "name":"jhon"
        }
]}

i want to convert this this jsonarray to List<Empolyee> . for this i had added the the maven dependency "camel-jackson" and also write the pojo class for employee . but when i try to run my below code

 ObjectMapper mapper = new ObjectMapper();
 List<Employe> list = mapper.readValue(jsonString, TypeFactory.collectionType(List.class, Employe.class));

am getting the following exception.

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
 at [Source: java.io.StringReader@43caa144; line: 1, column: 1]

can someone pls tell what am missing or doing anyting wrong

Answer 1

I also faced the similar problem with JSON output format. This code worked for me with the above JSON format.

package com.test.ameba;

import java.util.List;

public class OutputRanges {
    public List<Range> OutputRanges;
    public String Message;
    public String Entity;

    /**
     * @return the outputRanges
     */
    public List<Range> getOutputRanges() {
        return OutputRanges;
    }

    /**
     * @param outputRanges the outputRanges to set
     */
    public void setOutputRanges(List<Range> outputRanges) {
        OutputRanges = outputRanges;
    }

    /**
     * @return the message
     */
    public String getMessage() {
        return Message;
    }

    /**
     * @param message the message to set
     */
    public void setMessage(String message) {
        Message = message;
    }

    /**
     * @return the entity
     */
    public String getEntity() {
        return Entity;
    }

    /**
     * @param entity the entity to set
     */
    public void setEntity(String entity) {
        Entity = entity;
    }
}

package com.test;


public class Range {
    public String Name;
    /**
     * @return the name
     */
    public String getName() {
        return Name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        Name = name;
    }

    public Object[] Value;
    /**
     * @return the value
     */
    public Object[] getValue() {
        return Value;
    }
    /**
     * @param value the value to set
     */
    public void setValue(Object[] value) {
        Value = value;
    }

}

package com.test.ameba;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JSONTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String jsonString ="{\"OutputRanges\":[{\"Name\":\"ABF_MEDICAL_RELATIVITY\",\"Value\":[[1.3628407124839714]]},{\"Name\":\" ABF_RX_RELATIVITY\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_Unique_ID_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_FIRST_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_AMEBA_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_Effective_Date_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_AMEBA_MODEL\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_UC_ER_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_INN_OON_DED_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_COINSURANCE_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PCP_SPEC_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_INN_OON_OOP_MAX_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_IP_OP_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PHARMACY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PLAN_ADMIN_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]}],\"Message\":\"\",\"Entity\":null}";
        ObjectMapper mapper = new ObjectMapper();
        OutputRanges OutputRanges=null;
        try {
            OutputRanges = mapper.readValue(jsonString, OutputRanges.class);
        } catch (JsonParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("OutputRanges :: "+OutputRanges);;
        System.out.println("OutputRanges.getOutputRanges() :: "+OutputRanges.getOutputRanges());;
        for (Range r : OutputRanges.getOutputRanges()) {
            System.out.println(r.getName());
        }
    }

}

Answer 2

private static String readAll(Reader rd) throws IOException {
    StringBuilder sb = new StringBuilder();
    int cp;
    while ((cp = rd.read()) != -1) {
      sb.append((char) cp);
    }
    return sb.toString();
  }

 String jsonText = readAll(inputofyourjsonstream);
 JSONObject json = new JSONObject(jsonText);
 JSONArray arr = json.getJSONArray("Compemployes");

Your arr would looks like: [ { "id":1001, "name":"jhon" }, { "id":1002, "name":"jhon" } ] You can use:

arr.getJSONObject(index)

to get the objects inside of the array.

Answer 3

I had similar json response coming from client. Created one main list class, and one POJO class.

Answer 4

/*
 It has been answered in http://stackoverflow.com/questions/15609306/convert-string-to-json-array/33292260#33292260
 * put string into file jsonFileArr.json
 * [{"username":"Hello","email":"hello@email.com","credits"
 * :"100","twitter_username":""},
 * {"username":"Goodbye","email":"goodbye@email.com"
 * ,"credits":"0","twitter_username":""},
 * {"username":"mlsilva","email":"mlsilva@email.com"
 * ,"credits":"524","twitter_username":""},
 * {"username":"fsouza","email":"fsouza@email.com"
 * ,"credits":"1052","twitter_username":""}]
 */

public class TestaGsonLista {

public static void main(String[] args) {
Gson gson = new Gson();
 try {
    BufferedReader br = new BufferedReader(new FileReader(
            "C:\\Temp\\jsonFileArr.json"));
    JsonArray jsonArray = new JsonParser().parse(br).getAsJsonArray();
    for (int i = 0; i < jsonArray.size(); i++) {
        JsonElement str = jsonArray.get(i);
        Usuario obj = gson.fromJson(str, Usuario.class);
        //use the add method from the list and returns it.
        System.out.println(obj);
        System.out.println(str);
        System.out.println("-------");
    }
 } catch (IOException e) {
    e.printStackTrace();
 }
}

Answer 5

The problem is not in your code but in your json:

{"Compemployes":[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]}

this represents an object which contains a property Compemployes which is a list of Employee. In that case you should create that object like:

class EmployeList{
    private List<Employe> compemployes;
    (with getter an setter)
}

and to deserialize the json simply do:

EmployeList employeList = mapper.readValue(jsonString,EmployeList.class);

If your json should directly represent a list of employees it should look like:

[{"id":1001,"name":"jhon"}, {"id":1002,"name":"jhon"}]

Last remark:

List<Employee> list2 = mapper.readValue(jsonString, 
TypeFactory.collectionType(List.class, Employee.class));

TypeFactory.collectionType is deprecated you should now use something like:

List<Employee> list = mapper.readValue(jsonString,
TypeFactory.defaultInstance().constructCollectionType(List.class,  
   Employee.class));