Java: Simple HTTPUrlConnection example

I’ve been a little lax in posting lately. Since I have been doing a little more network based programming in Java as of late, and I wanted to post some more basic programming articles, I felt I would kill two birds with one stone. Fortunately most of it has been simple HTTP based requests, so it has been pretty simple stuff in terms of implementation. Most of how to do so is well documented already, so I won’t echo what has been written better by others. Instead, I will just share a simple example of how to establish an HTTP GET request using the HttpURLConnection and display the results to the console.

package com.digiassn.blogspot;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;

public class SimpleHTTPRequest {

  /**
   * @param args
   */
  public static void main(String[] args) {
      HttpURLConnection connection = null;
      OutputStreamWriter wr = null;
      BufferedReader rd  = null;
      StringBuilder sb = null;
      String line = null;
    
      URL serverAddress = null;
    
      try {
          serverAddress = new URL("http://localhost");
          //set up out communications stuff
          connection = null;
        
          //Set up the initial connection
          connection = (HttpURLConnection)serverAddress.openConnection();
          connection.setRequestMethod("GET");
          connection.setDoOutput(true);
          connection.setReadTimeout(10000);
                    
          connection.connect();
        
          //get the output stream writer and write the output to the server
          //not needed in this example
          //wr = new OutputStreamWriter(connection.getOutputStream());
          //wr.write("");
          //wr.flush();
        
          //read the result from the server
          rd  = new BufferedReader(new InputStreamReader(connection.getInputStream()));
          sb = new StringBuilder();
        
          while ((line = rd.readLine()) != null)
          {
              sb.append(line + '\n');
          }
        
          System.out.println(sb.toString());
                    
      } catch (MalformedURLException e) {
          e.printStackTrace();
      } catch (ProtocolException e) {
          e.printStackTrace();
      } catch (IOException e) {
          e.printStackTrace();
      }
      finally
      {
          //close the connection, set all objects to null
          connection.disconnect();
          rd = null;
          sb = null;
          wr = null;
          connection = null;
      }
  }
}

Next post will show how to use the Apache HTTPClient to establish a Multi-Part form POST request.