How to get JSON data into Servlet as parameter

Question

I am trying to write my first JSON servlet as following:

import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.json.JSONObject;
import org.json.JSONException;

public class Home extends HttpServlet{  

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req, HttpServletResponse res)throws ServletException, IOException{      
        res.setContentType("text/html; charset=UTF-8");
        req.setCharacterEncoding("UTF-8");
        res.setCharacterEncoding("UTF-8");      
        StringWriter sWriter    = new StringWriter();  
        PrintWriter out         = new PrintWriter(sWriter);                     

        String jsonText         = "{\"Name\":\"Vahid\",\"Nickname\":null,\"Salary\":\"15000.0\",\"isPermanent\":true,\"EmployeeId\":\"121\"}";      
        try{
            JSONObject json = new JSONObject(jsonText);       
            String name = json.getString("Name");
            out.println(json.toString()+"<br>"+"Name = "+name);
        }catch(JSONException e){
            e.printStackTrace();
        }

        res.getWriter().print(sWriter.toString());
        out.flush();
        out.close();
    }//doGet        
}//class

This code is working fine and giving me this output:

{"Name":"Vahid","Nickname":null,"Salary":"15000.0","EmployeeId":"121","isPermanent":true}
Name = Vahid

My question is how can I get JSON Object as a whole (as POST request) in my servlet from client browser e.g. request.getParameter("?????"); //what will be parameter name of JSON object? OR I have to get one by one all elements of JSON object as request.getParameter("name");

UPDATE
Here is my html file:

    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
    <title>Insert title here</title>
    <script type="text/javascript" src="/js/jquery.min.js"></script>
    <script>
var form = $('#form1');
$(document).ready(function(){
     $('body').hide().fadeIn(5000);
$(".submit").click(function (e) {

$.ajax({
type: form.attr('method'),
url: form.attr('action'),
console.log(url);
data: $(form).serialize(),
         success: function(msg){

             var json = msg ;
             $('#json').val(json);   
                            }
        });

                                 });
                             });
</script>


<body><br>
<form name="input" action="/JSONServlet"  method="POST" id="form1"  enctype="text/plain">
First name: <input type="text" name="FirstName" id="Firstname" value=" "><br>
Last name: <input type="text" name="LastName" value=" "><br>
<br>
<input type="submit" value="Submit" class="submit">

</form>
</body>

When I write String name = request.getParameter("name"); then output is null

Here what am trying:

String name = request.getParameter("FirstName");
    System.out.println(name);
        PrintWriter out= response.getWriter();
        try{
            JSONObject json = new JSONObject(name);         
            out.println(json.get("name"));          
        }catch(JSONException e){
            e.printStackTrace();
        }

output is null

Darshan Mehta · Answer 1 · 2017-08-24T08:39:52.283

2

It depends on which technology you are using to send the POST request. Below is a javascript example to send the json data:

var data = {
  name : "Vahid"
};
var request = new XMLHttpRequest();
request.open("POST", <URL>, true);
request.setRequestHeader('Content-Type', 'application/json; charset=UTF-8');

request.send(JSON.stringify(data));

Update

Once you send the data, you can use request.getParameter() on the server side to retrieve it, e.g.:

String data = request.getParameter("param_name");

This will give you String representation of the json. You can then convert it into JSONObject like you have done in the example in question.

edited Aug 24 '17 at 08:39

answered Aug 24 '17 at 08:25

Darshan Mehta

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I am not talking about javascript but talking about servlet that how I shall fetch this data in my servlet when this is sent (POST) – Devdas Aug 24 '17 at 08:36
Please check my question update – Devdas Aug 24 '17 at 09:10
@Devdas could you check the developer toolbar of the browser and post the request payload that is being sent to the server? – Darshan Mehta Aug 24 '17 at 10:31

score 0 · Answer 2 · answered Aug 24 '17 at 15:52

OR I have to get one by one all elements of JSON object as request.getParameter("name");

Yes, if you pass a json object to the Servlet, you can get the individual field names like you normally do. One by one.

When I write String name = request.getParameter("name"); then output is null

This is because you are getting the wrong parameter.

Look at your form:

First name: <input type="text" name="FirstName" id="Firstname" value=" "><br>
Last name: <input type="text" name="LastName" value=" "><br>

To get the first name field you must call 'FirstName' (name attribute).

So do this:

String name = request.getParameter("FirstName");

You also don't need

value=" "

or

id="FirstName"

Just do:

<form name="input" action="/JSONServlet"  method="POST" id="form1">
First name: <input type="text" name="FirstName"/><br>
Last name: <input type="text" name="LastName"/><br>
<br>
<input type="submit" value="Submit" class="submit">
</form>

remove this also from form tag:

enctype="text/plain"

thanks @Jonathan. You said Yes,` if you pass a json object to the Servlet, you can get the individual field names like you normally do. One by one.` My question is before this step i.e. how can I get `{"email":"vahid@gmail.com","name":"Vahid","Code":"101","info":"Success"}` in servlet then I shall split it — Devdas, Aug 24 '17 at 16:29

How to get JSON data into Servlet as parameter

2 Answers2