CODEWITHSUNDEEP
javaproxyreverse-proxyundertow
Sriram Sridharan
Sriram Sridharan

Reputation: 740

Undertow - How to Setup a Reverse Proxy to Monitor HTTP/HTTPS Traffic to my REST API

I would like to basically sniff HTTP/HTTPS requests and responses from my computer to a remote URL (basically a REST API). I understand there are plenty of tools that will help me get what I want, but I have to kind of write a utility to do this in Java (as this's going to be used by some applications we are developing).

What I want to do is set up a proxy (or a reverse proxy - my understanding of the terms is limited here), through which I route all my requests to real APIs. This proxy must Capture the Request body (in case of a POST or PUT) and forward the request to the real API, capture its response and send it back to the client.

I came across Undertow, using which I was able to create and run a Reverse Proxy using its LoadBalancingProxyClient proxy client. But I have a few questions here.

Assume my API is http://myrealapplication.com/rest/operation1, and I want to POST a JSON to this API.

I have created a proxy server as follows:

        LoadBalancingProxyClient loadBalancer = new LoadBalancingProxyClient();
        loadBalancer.addHost(new URI("http://myrealapplication.com"));
        loadBalancer.setConnectionsPerThread(20);

        Undertow reverseProxy = Undertow.builder()
                .addHttpListener(8990, "localhost")
                .setIoThreads(4)
                .setHandler(Handlers.requestDump(new ProxyHandler(loadBalancer, 3000, null)))
                .build();
        reverseProxy.start();

So once I've started my Reverse Proxy server, there are two things:

  1. My reverse proxy has practically become sort of an alias for my real API, but how do I capture the request and response in this layer?
  2. With the above setup, in order for my request to pass through this proxy, I have to change my URL to http://localhost:8990/rest/operation1, which may not be acceptable, as what we are expecting to do is to set up localhost:8990 as a Proxy, and keep my URL as http://myrealapplication.com/rest/operation1, so that it looks to the end client as the response is coming from the actual API.

Can I use undertow to achieve this? Or are there any other tools which expose a Java API which I can use in my programs?

Please help!

Thanks, Sriram

Upvotes: 2

Views: 2365

Answers (1)

Miere
Miere

Reputation: 1595

I think that what you are actually looking for is a Forward Proxy. Here is sample code which would help you to create one.

public class ForwardProxyWithUndertow {

  public static void main( String[] args ) {
    final HttpHandler forwardProxyHandler = new ConnectHandler(ForwardProxyWithUndertow::handleNotFound );

    Undertow.builder()
      .addHttpListener(8080, "localhost")
      .setHandler( forwardProxyHandler )
      .build()
      .start();
  }

  static void handleNotFound( HttpServerExchange e ){
    e.setStatusCode(404);
    e.endExchange();
  }
}

Hope it helps! ;)

Upvotes: 1

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