Forward HttpServletRequest to a different server

Question

I got a HttpServletRequest request in my Spring Servlet which I would like to forward AS-IS (i.e. GET or POST content) to a different server.

What would be

Answer 1

I also needed to do the same, and after some non optimal with Spring controllers and RestTemplate, I found a better solution: Smiley's HTTP Proxy Servlet. The benefit is, it really does AS-IS proxying, just like Apache's mod_proxy, and it does it in a streaming way, without caching the full request/response in the memory.

Simply, you register a new servlet to the path you want to proxy to another server, and give this servlet the target host as an init parameter. If you are using a traditional web application with a web.xml, you can configure it like following:

    proxy
    org.mitre.dsmiley.httpproxy.ProxyServlet
    
      targetUri
      http://target.uri/target.path
    


  proxy
  /mapping-path/*

or, of course, you can go with the annotation config.

If you are using Spring Boot, it is even easier: You only need to create a bean of type ServletRegistrationBean, with the required configuration:

@Bean
public ServletRegistrationBean proxyServletRegistrationBean() {
    ServletRegistrationBean bean = new ServletRegistrationBean(
            new ProxyServlet(), "/mapping-path/*");
    bean.addInitParameter("targetUri", "http://target.uri/target.path");
    return bean;
}

This way, you can also use the Spring properties that are available in the environment.

You can even extend the class ProxyServlet and override its methods to customize request/response headers etc, in case you need.

Update: After using Smiley's proxy servlet for some time, we had some timeout issues, it was not working reliably. Switched to Zuul from Netflix, didn't have any problems after that. A tutorial on configuring it with Spring Boot can be found on this link.