Error Parsing json string sent from js to Java

Question

I am tring to send a json string from js to servlet. I use ajax jquery to post to the servlet.

I can see the servlet post getting called but an exception occurs when I retrieve the json string in java, what am I missing

Javascript side:

var jsonText = JSON.stringify(SomeString);

    $.ajax({
        dataType: 'json',
        url: fullpath,
        type: 'POST',
        data: jsonText 
  });

Java side:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;
import java.io.PrintWriter;

import com.json.JSONException;
import com.json.JSONObject;
import com.json.JSONArray;

In post

    response.setContentType("application/json");    
JSONObject jObj = new JSONObject(request.getParameter("jsonText"));//Null pointer exception

Error:

 java.lang.NullPointerException
        at java.io.StringReader.<init>(StringReader.java:33)
        at com.json.JSONTokener.<init>(JSONTokener.java:84)
        at com.json.JSONObject.<init>(JSONObject.java:314)

JSON string:

{ "CustomerDetails": [{'name':'Amy','age':'23'},{'name':'Amj','age':'25'},{'name':'Amg','age':'27'}]}

You get null pointer at response.setContentType("application/json"); OR JSONObject jObj = new JSONObject(request.getParameter("jsonText")); — arahant
– arahant, Commented Aug 1, 2012 at 16:01
When posting JSON, there would not be a parameter named jsonText. Just because that is what the JSON body is called in javascript, does not mean that there is a parameter named that, unless you specifically created a query string with that as one of the keys. — Mike Brant
– Mike Brant, Commented Aug 1, 2012 at 16:04

gen_Eric · Accepted Answer · 2012-08-01 16:06:41Z

2

In your POST, there is no jsonText parameter. You're just posting the JSON string as the post body.

Try to send it like this:

$.ajax({
    dataType: 'json',
    url: fullpath,
    type: 'POST',
    data: {jsonText: jsonText}
});

answered Aug 1, 2012 at 16:06

gen_Eric

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5 Comments

Haran Murthy Over a year ago

With this request.getParameter("jsonText") should work right, let me try

Haran Murthy Over a year ago

shouldn't it be data: {'jsonText': jsonText}?

gen_Eric Over a year ago

Yes, now your Java code should work. Also, you don't need to quote the keys in a JavaScript object.

apsillers Over a year ago

For the sake of completeness: if you can't alter what the client sends, you can get the POST data by reading it out as a String from request.getInputStream() and then passing that String into the JSONObject constructor. However, Rocket's solution is much simpler, as long as you can alter the client behavior.

gen_Eric Over a year ago

@apsillers: Yes, that works too. I usually don't read from the raw post body unless I have to. :-P

arahant · Accepted Answer · 2012-08-01 16:05:09Z

0

This suggests there is no POST parameter called jsonText

answered Aug 1, 2012 at 16:05

arahant

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1 Comment

apsillers Over a year ago

This should probably be a comment, not an answer.

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