Plain handler interface for components that process HTTP requests, analogous to a Servlet. Only declares {@link javax.servlet.ServletException}and {@link java.io.IOException}, to allow for usage within any {@link javax.servlet.http.HttpServlet}}. This interface is essentially the direct equivalent of an HttpServlet, reduced to a central handle method.
The easiest way to expose an HttpRequestHandler bean in Spring style is to define it in Spring's root web application context and define an {@link org.springframework.web.context.support.HttpRequestHandlerServlet}in web.xml, pointing at the target HttpRequestHandler bean through its servlet-name which needs to match the target bean name.
Supported as a handler type within Spring's {@link org.springframework.web.servlet.DispatcherServlet}, being able to interact with the dispatcher's advanced mapping and interception facilities. This is the recommended way of exposing an HttpRequestHandler, while keeping the handler implementations free of direct dependencies on a DispatcherServlet environment.
Typically implemented to generate binary responses directly, with no separate view resource involved. This differentiates it from a {@link org.springframework.web.servlet.mvc.Controller} within Spring's Web MVCframework. The lack of a {@link org.springframework.web.servlet.ModelAndView}return value gives a clearer signature to callers other than the DispatcherServlet, indicating that there will never be a view to render.
As of Spring 2.0, Spring's HTTP-based remote exporters, such as {@link org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter}and {@link org.springframework.remoting.caucho.HessianServiceExporter}, implement this interface rather than the more extensive Controller interface, for minimal dependencies on Spring-specific web infrastructure.
Note that HttpRequestHandlers may optionally implement the {@link org.springframework.web.servlet.mvc.LastModified} interface,just like Controllers can, provided that they run within Spring's DispatcherServlet. However, this is usually not necessary, since HttpRequestHandlers typically only support POST requests to begin with. Alternatively, a handler may implement the "If-Modified-Since" HTTP header processing manually within its handle method.
@author Juergen Hoeller
@since 2.0
@see org.springframework.web.context.support.HttpRequestHandlerServlet
@see org.springframework.web.servlet.DispatcherServlet
@see org.springframework.web.servlet.ModelAndView
@see org.springframework.web.servlet.mvc.Controller
@see org.springframework.web.servlet.mvc.LastModified
@see org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter
@see org.springframework.remoting.httpinvoker.HttpInvokerServiceExporter
@see org.springframework.remoting.caucho.HessianServiceExporter
@see org.springframework.remoting.caucho.BurlapServiceExporter