ANSWER:

As was already mentioned, caching proxies should do the trick for you (BTW, this is the simplest solution). There are quite a lot of different implementations, so you just need to spend some time selecting a proper one (according to my experience squid is a good solution). Anyway, I would like to highlight two other interesting options:

Option 1: Betamax

Betamax is a tool for mocking external HTTP resources such as web services and REST APIs in your tests. The project was inspired by the VCR library for Ruby. Betamax aims to solve these problems by intercepting HTTP connections initiated by your application and replaying previously recorded responses.

Betamax comes in two flavors. The first is an HTTP and HTTPS proxy that can intercept traffic made in any way that respects Java’s http.proxyHost and http.proxyPort system properties. The second is a simple wrapper for Apache HttpClient.

BTW, Betamax has a very interesting feature for you:

Betamax is a testing tool and not a spec-compliant HTTP proxy. It ignores any and all headers that would normally be used to prevent a proxy caching or storing HTTP traffic.

Option 2: Wireshark and replay proxy

Grab all traffic you are interested in using Wireshark and replay it. This I would say it is not that hard to implement required replaying tool, but you can use available solution called replayproxy

Replayproxy parses HTTP streams from .pcap files
opens a TCP socket on port 3128 and listens as a HTTP proxy using the extracted HTTP responses as a cache while refusing all requests for unknown URLs.

Such approach provide you with the full control and bit-to-bit precise simulation.

Renat Gilmanov from http://stackoverflow.com/questions/16623906