I will need to implement my own version of HttpSession in Java. I have found very little information which explains how achieve such a feat.
I guess my problem is - how do I override the existing HttpSession no matter the application server's implementation?
I did run across a quality but rather old read which helps me achieve my goal - http://java.sun.com/developer/technicalArticles/Servlets/ServletControl/
Are there any other approaches?
Its two ways.
"Wrapping" the original HttpSession in your own HttpServletRequestWrapper implementation.
I made this a short time ago for clustering distributed sessions with Hazelcast and Spring Session.
Here is explained pretty well.
First, implement your own HttpServletRequestWrapper
public class SessionRepositoryRequestWrapper extends HttpServletRequestWrapper {
public SessionRepositoryRequestWrapper(HttpServletRequest original) {
super(original);
}
public HttpSession getSession() {
return getSession(true);
}
public HttpSession getSession(boolean createNew) {
// create an HttpSession implementation from Spring Session
}
// ... other methods delegate to the original HttpServletRequest ...
}
After, from your own Filter, wraps the original HttpSession, and put it inside the FilterChain provided by your Servlet Container.
public class SessionRepositoryFilter implements Filter {
public doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
HttpServletRequest httpRequest = (HttpServletRequest) request;
SessionRepositoryRequestWrapper customRequest =
new SessionRepositoryRequestWrapper(httpRequest);
chain.doFilter(customRequest, response, chain);
}
// ...
}
Finally, set your Filter at the beginning in the web.xml to ensure it performs before any other.
The second manner to achieve it is providing to your Servlet Container your custom SessionManager.
For example, in Tomcat 7.
Create a new class, and implement HttpSession:
public class MyHttpSession implements javax.servlet.http.HttpSession {
// and implement all the methods
}
Disclaimer: I have not tested this myself:
Then write a filter with a url-pattern of /* and extend HttpServletRequestWrapper. Your wrapper should return your custom HttpSession class in getSession(boolean).
In the filter, use your own HttpServletRequestWrapper.
HttpServletRequestWrapper you override both getSession methods to return your custom Session implementation.It doesn't seem like it's easily doable in a portable fashion that would work among different containers, since the HttpSession implementation is provided by the J2EE container.
However, to achieve a similar result, you can implement a javax.servlet.Filter and javax.servlet.HttpSessionListener and in your filter, wrap the ServletRequest and ServletResponse, such as described in Spring Boot with Hazelcast and Tomcat.
