如何将数据列表转换为json

Question

I want the following json ,where List<form> will have list of form_id , form_name , how can I convert this using jsonobject, I am not getting the proper json output. Please help me with this. Json:

{
    "forms": [
        { "form_id": "1", "form_name": "test1" },
        { "form_id": "2", "form_name": "test2" } 
    ]
}

The above is the json structure that i need it for a list.Where id ,name is a list from form object

public static JSONObject getJsonFromMyFormObject(List<Form> form) {
    JSONObject responseDetailsJson = new JSONObject();
    JSONArray jsonArray = null;
    System.out.println(form.size());
    for (int i = 0; i < form.size(); i++) {
        JSONObject formDetailsJson = new JSONObject();
        formDetailsJson.put("form_id", form.get(i).getId());
        formDetailsJson.put("form_name", form.get(i).getName());
        jsonArray = new JSONArray();
        jsonArray.add(formDetailsJson);
    }
    responseDetailsJson.put("form", jsonArray);
    return responseDetailsJson;

} 

Facing issue here not getting output as a list

Answer 1

The code in the original question is close to achieving the described desired result. Just move the JSONArray instance creation outside of the loop.

import java.util.ArrayList;
import java.util.List;

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;

public class Foo
{
  public static JSONObject getJsonFromMyFormObject(List<Form> form)
  {
    JSONObject responseDetailsJson = new JSONObject();
    JSONArray jsonArray = new JSONArray();

    for (int i = 0; i < form.size(); i++)
    {
      JSONObject formDetailsJson = new JSONObject();
      formDetailsJson.put("form_id", form.get(i).getId());
      formDetailsJson.put("form_name", form.get(i).getName());

      jsonArray.add(formDetailsJson);
    }
    responseDetailsJson.put("forms", jsonArray);
    return responseDetailsJson;
  }

  public static void main(String[] args)
  {
    List<Form> forms = new ArrayList<Form>();
    forms.add(new Form("1", "test1"));
    forms.add(new Form("2", "test2"));

    JSONObject jsonObject = getJsonFromMyFormObject(forms);
    System.out.println(jsonObject);
  }
}

class Form
{
  String id;
  String name;

  Form(String i, String n)
  {
    id = i;
    name = n;
  }

  String getId()
  {
    return id;
  }

  String getName()
  {
    return name;
  }
}

Answer 2

Properbly http://www.roseindia.net/tutorials/json/jsonobject-java-example.shtml will help.

According the comment from Tushar, here the extract from the aboved linked website:

Now in this part you will study how to use JSON in Java. To have functionality of JSON in java you must have JSON-lib. JSON-lib also requires following "JAR" files:

1. commons-lang.jar

2. commons-beanutils.jar

3. commons-collections.jar

4. commons-logging.jar

5. ezmorph.jar

6. json-lib-2.2.2-jdk15.jar

JSON-lib is a java library for that transforms beans, collections, maps, java arrays and XML to JSON and then for retransforming them back to beans, collections, maps and others. In this example we are going to use JSONObject class for creating an object of JSONObject and then we will print these object value. For using JSONObject class we have to import following package "net.sf.json". To add elements in this object we have used put() method. Here is the full example code of FirstJSONJava.java is as follows:

FirstJSONJava.java

    import net.sf.json.JSONObject;

    public class FirstJSONJava
    {
       public static void main(String args[])
       {
        JSONObject object=new JSONObject();
         object.put("name","Amit Kumar");
        object.put("Max.Marks",new Integer(100));
        object.put("Min.Marks",new Double(40));
        object.put("Scored",new Double(66.67));
        object.put("nickname","Amit");
        System.out.println(object);
      }
   } 

To run this example you have to follow these few steps as follows:

• Download JSON-lib jar and other supporting Jars

• Add these jars to your classpath

• Create and save FirstJSONJava.java

• Compile it and execute it.