How to build a HTTP POST Request with Java?

[Atli]

Hi everybody.

After years of C# and PHP, I'm finally returning to Java.
My goal is to create a Java program capable of sending images to a PHP Photo Album on my web server.

Right now, however, I am stuck trying to send simple text variables through POST to my PHP script.
The code does seem to connect to the script like it is supposed to, but it seems unable to send the POST variables. The PHP script is returning a 'Undefined index' warning for the variables, like they don't exists.

My Java Code:

public static void main(String[] args) {
    try {
        URL url;
        URLConnection urlConnection;
        DataOutputStream outStream;
        DataInputStream inStream;
 
        // Build request body
        String body =
        "fName=" + URLEncoder.encode("Atli", "UTF-8") +
        "&lName=" + URLEncoder.encode("Þór", "UTF-8");
 
        // Create connection
        url = new URL("http://192.168.1.68/test/POST/post.php");
        urlConnection = url.openConnection();
        ((HttpURLConnection)urlConnection).setRequestMethod("POST");
        urlConnection.setDoInput(true);
        urlConnection.setDoOutput(true);
        urlConnection.setUseCaches(false);
        urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        urlConnection.setRequestProperty("Content-Length", ""+ body.length());
 
        // Create I/O streams
        outStream = new DataOutputStream(urlConnection.getOutputStream());
        inStream = new DataInputStream(urlConnection.getInputStream());
 
        // Send request
        outStream.writeBytes(body);
        outStream.flush();
        outStream.close();
 
        // Get Response
        // - For debugging purposes only!
        String buffer;
        while((buffer = inStream.readLine()) != null) {
            System.out.println(buffer);
        }
 
        // Close I/O streams
        inStream.close();
        outStream.close();
    }
    catch(Exception ex) {
        System.out.println("Exception cought:\n"+ ex.toString());
    }
}
 

And the PHP code:

<?php
    # Read GET variables
    $fName = $_POST['fName'];
    $lName = $_POST['lName'];
 
    # Create output string
    $str = "\"$fName\", \"$lName\"\n";
 
    # Open and write to file
    $fh = fopen("postData.txt", "a+");
    fwrite($fh, $str);
    fclose($fh);
 
    echo "done";
?>
 

Any thoughts?
Thanks.

[ak1dnar]

Some where from the internet:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
 
public class POSTDATA {
 
 
    public POSTDATA() {
    }
    public static void main(String[] args) {
        try {
        // Construct data
        String data = URLEncoder.encode("fName", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8");
        data += "&" + URLEncoder.encode("lName", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8");
 
        // Send data
        URL url = new URL("http://localhost/TUT/POSTDATA/post.php");
        URLConnection conn = url.openConnection();
        conn.setDoOutput(true);
        OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
        wr.write(data);
        wr.flush();
 
        // Get the response
        BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String line;
        while ((line = rd.readLine()) != null) {
            System.out.println(line);
        }
        wr.close();
        rd.close();
    } catch (Exception e) {
    }
    }
 
}
 
 
 

[Atli]

Thank you for that!

After comparing my code to yours I realized that my mistake was to call the 'urlConnection.getInputStream()' method (line 25) before I sent the request. It appears to send the request when this method is called, ignoring any future changes to it.

Thanks again, ajaxrand.

[ak1dnar]

Welcome. And this also will helpul Atli.

java.io.DataInputStream.readLine()
This method does not properly convert bytes to characters. As of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method. Programs that use the DataInputStream class to read lines can be converted to use the BufferedReader class by replacing code of the form:

  DataInputStream d = new DataInputStream(in);

with:

 BufferedReader d
          = new BufferedReader(new InputStreamReader(in));
 

[freddieMaize]

May I cont.with this old thread?

Below is my login jsp page]

    <form action="success.jsp" method="POST">
    <input type="text" name="fname" value="" />
    <input type="text" name="lname" value="" />

Below is my success jsp page

 
        out.println("first name "+request.getParameter("fname"));
        out.println("last name "+request.getParameter("lname"));
if (request.getParameter("fname").equalsIgnoreCase("freddie")&&request.getParameter("lname").equalsIgnoreCase("maize")){
          out.println("Successful Login");
        }
        else{
          out.println("Login failed");
        }

When I try to login using my Java POST method (using the code that is posted above) I'm getting login failed. Below is how it looks like,

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>       
        <h2>Hello World!</h2>
        first name freddielname=maize
last name null
Login failed
    </body>
</html>
 

If you see the first out.print(), i'm getting both the fname and lname there which should not be. How do i deal this? Thanks

fREDDIE

[freddieMaize]

@freddieMaize
Resolved. Used below,

        String body = 
        "fName=" + URLEncoder.encode("Atli", "UTF-8") + 
        "&lName=" + URLEncoder.encode("Þór", "UTF-8"); 

instead of below

 String data = URLEncoder.encode("fName", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8"); 
        data += "&" + URLEncoder.encode("lName", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8")

Thanks