Set custom response in Spring interceptor - spring

Question

Here is my interceptor method where i want to set custom response to tell the UI what happened
#Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
HttpSession session = request.getSession(false);
if (session != null)
return true;
else{
response.sendError(HttpServletResponse.SC_REQUEST_TIMEOUT)
return false;
}
}
And in web.xml
<error-page>
<error-code>408</error-code>
<location>/error.html</location>
</error-page>
spring-servlet.xml
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**" />
<mvc:exclude-mapping path="/login" />
<bean class="com.example.CustomInterceptor" />
</mvc:interceptor>
</mvc:interceptors>
When the session is timed out its not sending any response after return false.
Even the below is not working
response.sendRedirect("http://localhost:8080/home");

Answer 1

You can try very simple thing. Change your mvc:interceptros structure to
<mvc:interceptors>
<bean class="com.example.CustomInterceptor" />
</mvc:interceptors>
This essentially mean apply the interceptor to all applicable requests. I will come in a moment to why I say applicable in a moment. If above works then the issue is with your mapping.
Now as you know interceptors are configured at the level of HandlerMapping and it will be RequestMappingHandlerMapping (Spring 3.1+ with mvc:annotation-driven) or DefaultAnnotationHandlerMapping in your case.
Now as you have use <mvc:mapping path="/**" /> will map to all requests (including subpaths) as long as they are valid mappings. So lets say you have controller
#RequestMapping(value="/home", method = RequestMethod.GET)
public String welcome() {
return "welcome";
}
you cannot hit http://localhost:8080/yourProjectName/home/test and expect it to hit the interceptor. So you have to hit http://localhost:8080/yourProjectName/home as that is a valid HandlerMapping.
As to to response first debug if your interceptor is getting hit for any requests. If it does work then
response.sendError(HttpServletResponse.SC_REQUEST_TIMEOUT);
should redirect you to error.html as you have used
<error-page>
<error-code>408</error-code>
<location>/error.html</location>
</error-page>