HTTP URLConnection with proxy in Java

Since Java 1.5 you can also pass a java.net.Proxy instance to the openConnection() method in order to access an URL using a proxy server. If your proxy requires authentication it should give you response 407, but this depends on the proxy server settings. Here is an example how to add the proxy settings to the URLConnection, both situations with authentication or not are covered. The test server used is http://httpbin.org/get and the response is a JSON object with details about the request. For more details also check the code comments.

Code

package com.adm;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.Authenticator;
import java.net.InetSocketAddress;
import java.net.PasswordAuthentication;
import java.net.Proxy;
import java.net.URL;
import java.net.URLConnection;

public class URLConnectionProxy {

    /**
     * The User Agent
     */
    private static final String AGENT = "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)";

    /**
     * Used to store the proxy settings
     */
    private Proxy proxy;

    /**
     * 
     * Method used to add proxy settings
     *
     * @param ip
     *            the proxy IP
     * @param port
     *            the proxy port
     */
    public void setProxy(String ip, int port) {
	this.proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip, port));
    }

    /**
     * 
     * Method used to add proxy settings with authentication
     *
     * @param ip
     * @param port
     * @param username
     * @param password
     */
    public void setProxy(String ip, int port, String username, String password) {
	this.proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress(ip, port));
	Authenticator authenticator = new Authenticator() {

	    public PasswordAuthentication getPasswordAuthentication() {
		return (new PasswordAuthentication(username, password.toCharArray()));
	    }
	};
	Authenticator.setDefault(authenticator);

    }

    /**
     * The method will return the content in a {@link InputStream} object
     * 
     * @param domain
     *            The Domain name
     * 
     * @return the content as {@link InputStream} object
     * @throws Exception
     */
    private InputStream getContent(String domain) throws Exception {

	URL url = new URL(domain);
	URLConnection connection = null;
	if (this.proxy != null)
	    connection = url.openConnection(this.proxy);
	else
	    connection = url.openConnection();

	connection.setRequestProperty("User-Agent", AGENT);
	return connection.getInputStream();
    }

    /**
     * Method used to get URL content in {@link String} format
     * 
     * @param domain
     *            the {@link String} the URL
     * @return the {@link String} object returned
     * @throws Exception
     */
    public String getString(String domain) throws Exception {
	InputStream is = getContent(domain);
	StringBuilder sb = new StringBuilder();

	BufferedReader br = new BufferedReader(new InputStreamReader(is));
	String line;
	try {
	    while ((line = br.readLine()) != null) {
		sb.append(line);
	    }
	} catch (IOException e) {
	    e.printStackTrace();
	} finally {
	    /** finally block to close the {@link BufferedReader} */
	    if (br != null) {
		try {
		    br.close();
		} catch (IOException e) {
		    e.printStackTrace();
		}
	    }
	}
	return sb.toString();
    }

    public static void main(String[] args) throws Exception {
	System.out.println("URLConnection with Proxy Example");
	System.out.println();

	String url = "http://httpbin.org/get";

	URLConnectionProxy con = new URLConnectionProxy();

	/**
	 * activate this line if you are behind a proxy server - change the settings
	 * accordingly
	 */
	con.setProxy("127.0.0.1", 7000);

	/**
	 * activate this line if you are behind a proxy server with authentication -
	 * change the settings accordingly
	 */
	// con.setProxy("127.0.0.1", 7000, "user", "passowrd");

	String result = con.getString(url);

	System.out.println("URL: " + url);
	System.out.println();
	System.out.println(result);
    }
}

Output

URLConnection with Proxy Example

URL: http://httpbin.org/get

{  "args": {},   "headers": {    "Accept": "text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2",     "Cache-Control": "max-age=259200",     "Connection": "close",     "Host": "httpbin.org",     "User-Agent": "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)"  },   "origin": "11.11.11.11, 22.22.22.22",   "url": "http://httpbin.org/get"}

References

• URLConnection Javadoc
• Proxy Javadoc