i want change the host url of a java applet. I just played around with the burp proxy but there is no "Match and replace" for the host url. Instead of http://www.foo.com/abc/index.php?name=john the page http://www.bar.com/abc/index.php?name=john should be requested.
You can accomplish this through a reverse proxy.
Apache supports reverse proxies, though I find them to be a bit tricky to get working properly. Apache Reverse Proxies do offer quite a lot of control.
Another Reverse Proxy solution is "Pound". I find Pound reasonably easy to configure and use, though it's less feature rich than Apache's options.
There are many other reverse proxy solutions out there too. Some you can pay for, some even are implemented as hardware devices.