UrlRewriter is an open-source, light-weight, highly configurable
URL rewriting component for Java. It provides similar
capabilities that the Apache web server provides with
mod_rewrite and .htaccess.
Download JD-GUI to open JAR file and explore Java source code file (.class .java)
Click menu "File → Open File..." or just drag-and-drop the JAR file in the JD-GUI window urlrewriter-2.0RC1.jar file.
Once you open a JAR file, all the java classes in the JAR file will be displayed.