"Head first Servlets and JSP" Note 10: Request Dispatch (RequestDispatcher)

Let other components take over all requests

; Partial takeover request

Some questions--

The Intercept point is useful.

1. Let other components take over all requests.

 PackageCom.example.web;ImportCom.example.model.BeerExpert;Importjavax.servlet.*;Importjavax.servlet.http.*;ImportJava.io.*;ImportJava.util.*; Public classBeerselectextendsHttpServlet {@Overrideprotected voidDoPost (httpservletrequest req, HttpServletResponse resp)throwsservletexception, IOException {String C= Req.getparameter ("Color"); Beerexpert be=NewBeerexpert (); List result=Be.getbrands (c); Req.setattribute ( "Styles", result); Adds an attribute to the request for use by the JSP. RequestDispatcher view = Req.getrequestdispatcher ("result.jsp"); Instantiate a request dispatcher for JSP View.forward (req, resp); Use the request dispatcher to require the container to prepare the JSP and send requests and responses to the JSP    }}

Why not SendRequest ("result.jsp"), but RequestDispatcher?

2, RequestDispatcher secret.

Where do I get the requestdispatcher? --getrequestdispatcher

1. ServletRequest, you can use relative paths
2. ServletContext, the absolute path must be used, i.e. the path must begin with a "/".

How do I use RequestDispatcher?

1. Call Forward (). It is simple to pass in the request and response as parameters.
2. It is not necessary to be aware that it is illegal to forward () after responding to a commit (for example, Os.flush).

3. Attribute Scope

"Head first Servlets and JSP" Note 10: Request Dispatch (RequestDispatcher)