How to use an HTTP proxy in java

问题:

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 the server logs).

How can this be done through java?

回答1:

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.

回答2:

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);

回答3:

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