Encode and Decode JSON in Java using json-simple

Create a Maven project and add the following dependency to the project:

<dependency>
<groupId>com.googlecode.json-simple</groupId>
<artifactId>json-simple</artifactId>
<version>1.1.1</version>
</dependency>

Create plain old java obj, something as simple as follows:

package com.memeanalytics.json_demo;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DemoEntity {
 private String name = "";
 private Date createDate=new Date();
 private boolean enabled=false;
 private double value = 0;
 private int count = 0;
 
 public String getName()
 {
  return this.name;
 }
 
 public void setName(String name)
 {
  this.name=name;
 }
 
 public String getCreateDateString()
 {
  SimpleDateFormat formatter=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  return formatter.format(this.createDate);
 }
 
 public void setCreateDateString(String dateString)
 {
  SimpleDateFormat formatter=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  try {
   this.createDate = formatter.parse(dateString);
  } catch (ParseException e) {
   e.printStackTrace();
  }
 }
 
 public boolean isEnabled()
 {
  return this.enabled;
 }
 
 public void setEnabled(boolean enabled)
 {
  this.enabled=enabled;
 }
 
 public int getCount()
 {
  return this.count;
 }
 
 public int setCount(int count)
 {
  return this.count = count;
 }
 
 public double getValue() 
 {
  return this.value;
 }
 
 public void setValue(double value)
 {
  this.value=value;
 }
}

Create a utility class with two methods to encode and decode between JSON and the DemoEntity obj:

package com.memeanalytics.json_demo;

import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import org.json.simple.parser.ParseException;

public class JsonEncoder {
 public static String encode(DemoEntity obj)
 {
  JSONObject json=new JSONObject();
  
  json.put("name", obj.getName());
  json.put("createDate", obj.getCreateDateString());
  json.put("value", obj.getValue());
  json.put("count", obj.getCount());
  
  return json.toJSONString();
 }
 
 public static DemoEntity decode(String jsonString) 
 {
  JSONParser parser=new JSONParser();
  
  DemoEntity obj=null;
  
  try{
   JSONObject json = (JSONObject)parser.parse(jsonString);
   
   obj=new DemoEntity();
   obj.setName((String)json.get("name"));
   obj.setCreateDateString((String)json.get("createDate"));
   obj.setValue((Double)json.get("value"));
   obj.setCount(Integer.parseInt(json.get("count").toString()));
  }catch(ParseException ex)
  {
   ex.printStackTrace();
  }
  return obj;
 }
}

Now in the main class simply invokes the encode and decode methods to switch between JSON and DemoEntity obj:

package com.memeanalytics.json_demo;

public class App 
{
    public static void main( String[] args )
    {
     DemoEntity obj=new DemoEntity();
     
     obj.setName("obj1");
     obj.setValue(12.5);
     obj.setCount(10);
     
     String jsonString = JsonEncoder.encode(obj);
     System.out.println(jsonString);
     
     DemoEntity obj2  = JsonEncoder.decode(jsonString);
     
     if(obj2 != null)
     {
      System.out.println("name : " + obj2.getName());
      System.out.println("created date : " + obj2.getCreateDateString());
      System.out.println("value : "+obj2.getValue());
      System.out.println("count : "+obj2.getCount());
     }
    }
}

Two points to note:

1. for Date() object, i will be safer to convert it to String before put it into a JSONObject during serialization, and vice versa in deserialization.
2. for Integer object, it will be safer to covert the the item returned by JSONObject.get() to a String then parse it to integer during deserialization (as JSONObject.get() usually will return a Long object instead of an Integer object).

Below is the link to the complete source codes:

https://dl.dropboxusercontent.com/u/113201788/storm/json-demo.zip

Parse JSON string using JSON.Net

First add Newtonsoft.Json to the references of the project. Now suppose we want to parse the following JSON string which contains an array of objects:

"[{"id":"1","userid":"1","name":"node:19:1","datatype":"1","tag":"Node:19","public":"0","size":"488","engine":"5","time":1413697602,"value":"215"},..., {"id":"20", ...}]"

The C# code as as follows:

dynamic data = JsonConvert.DeserializeObject(json_string);
for (int i = 0; i < data.Count; ++i)
{
dynamic item = data[i];

string id = (string)item.id;
string name = (string)item.name;
string tag = (string)item.tag;
int time = (int)item.time;
string value = (string)item.value;

double dbl_value = 0;
double.TryParse(value, out dbl_value);

//do something about the item here
}