How to use an HTTP proxy in java

I am writing a code that connects to websites and checks some code, like a crawler. But I need to connect trough a proxy and change the IP address (so it doesn't show the client's IP in 开发者_开发问答the server logs).

How can this be done through java?

You can use the java system properties to set up a proxy or pass it as command line options.

You can find some details and samples here.

Ex: Before opening the connection

System.setProperty("http.proxyHost", "myProxyServer.com");
System.setProperty("http.proxyPort", "80");

Or you can use the default network proxies configured in the sytem

System.setProperty("java.net.useSystemProxies", "true");

Since Java 1.5 you can create a instance of proxy and pass it to the openConnection() method.

Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("123.0.0.1", 8080));
URL url = new URL("http://www.yahoo.com");
HttpURLConnection uc = (HttpURLConnection)url.openConnection(proxy);
uc.connect();

Or as lisak suggested, you can use some 3rd party libraries which supports your need better.

Or you can also use HttpClient which would suit your needs better. Check out the documentation, it's brief and very informative.

DefaultHttpClient httpclient = new DefaultHttpClient();

HttpHost proxy = new HttpHost("someproxy", 8080);
httpclient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY, proxy);

Proxy proxy = new Proxy(Proxy.Type.HTTP, new InetSocketAddress("123.0.0.1", 8080));
URL url = new URL("http://www.yahoo.com");
HttpURLConnection uc = (HttpURLConnection)url.openConnection(proxy);
uc.connect();

This worked for me. I was able to use the proxy for the specific connection or transfer. Earlier we were using System.setProperty which used to set it at system level and all the requests internal/external started using the same proxy.

Also Proxy.Type.HTTP works for both http and https