error while sending data from java code to PHP in localhost using HTTPPost request

Question

This is my java code to send data through HTTPPost request:

import java.io.*;
import java.net.*;
class HttpURLConnectionEx{
    public static void main(String[] args) throws Exception{    
    URL targetURL = new URL("http://localhost/JAVA/post.php");
    HttpURLConnection conn =(HttpURLConnection) targetURL.openConnection();
    String body= "fName="+ URLEncoder.encode("value1","UTF-8")+"&lName=" + URLEncoder.encode("value2","UTF-8");
    conn.setDoOutput(true);
    conn.setInstanceFollowRedirects(true);
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    conn.setRequestProperty("charset", "UTF-8");
    conn.setRequestProperty("Content-Length", Integer.toString(body.length()));
    try
    {
     OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream());
     out.write(body);

      // Get the response
      BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
      String line;
      while((line = rd.readLine()) != null) {
           System.out.println(line);
      }
      }catch(Exception e){
        e.printStackTrace();
      } 
   }
}

This is my PHP code present in localhost:

<?php
    $data = $_POST["fName"];
    $dbc = mysqli_connect('localhost','root','root123','JAVA')
           or die("error connecting to mysql server");
    $query = "INSERT INTO insert_table(data) VALUES('".$data."')";
    if($query){
        echo "data inserted sucessfully";
    }
    $result = mysqli_query($dbc,$query) or die("error querying database");
?>

This is the output i 'm getting when i run it in commandline:

Answer 1

A flush after the write is required.

 out.flush();

edit

Undefined index: fName

The php error is clear enough, isn't? The $_POST array doesn't contain your POST variables.

First I've checked on php side the content of the post with var_dump($_POST) and:

/* save the raw post to a file */
file_put_contents('/tmp/post.txt', file_get_contents('php://input'));

Both were empty, so I used wireshark to check the HTTP/POST content, it was done but with Content-Length: 0 and without body.

Few googles to something similar to your code and I noticed the flush that mean OutputStreamWriter is buffered and at the time of the post request the output could be not written (sent to the server) or only partially, a good reason for zero content-length.

At this point I think you don't need to use conn.setRequestProperty for "Content-Length", it should be updated according with your buffer content length.