Alternative Java Clients - RESTful Java with JAX-RS 2.0 - page 243

Caching

By default, HttpURLConnection will cache results based on the caching response headers
discussed in Chapter 11 . You must invoke HttpURLConnection.setUseCaches(false) to
turn off this feature.

Authentication

The HttpURLConnection class supports Basic, Digest, and Client Certificate Authentication.
Basic and Digest Authentication use the java.net.Authenticator API. Here's an example:

Authenticator . setDefault ( new new Authenticator () {

protected protected PasswordAuthentication getPasswordAuthentication () {

return return new new PasswordAuthentication ( "username, " password " . toCharArray ());

}

});

The setDefault() method is a static method of Authenticator . You pass in an
Authenticator instance that overrides the class's getPasswordAuthentication() method.
You return a java.net.PasswordAuthentication object that encapsulates the username
and password to access your server. When you do HttpURLConnection invocations, authen-
tication will automatically be set up for you using either Basic or Digest, depending on what
the server requires.

The weirdest part of the API is that it is driven by the static method setDefault() . The
problem with this is that your Authenticator is set VM-wide. So, doing authenticated re-
quests in multiple threads to different servers is a bit problematic with the basic example just
shown. You can address this by using java.lang.ThreadLocal variables to store username
and passwords:

public public class class MultiThreadedAuthenticator MultiThreadedAuthenticator extends extends Authenticator {

private private static static ThreadLocal < String > username = new new ThreadLocal < String >();

private private static static ThreadLocal < String > password = new new ThreadLocal < String >();

public public static void setThreadUsername ( String user ) {

username . set ( user );

static void

}

public public static void setThreadPassword ( String pwd ) {

password . set ( pwd );

static void

}

protected protected PasswordAuthentication getPasswordAuthentication () {