The RequestDispatcher is an Interface that comes under package javax.servlet. Using this interface we get an object in servlet after receiving the request. Using the RequestDispatcher object we send a request to other resources which include (servlet, HTML file, or JSP file). A RequestDispatcher object can be used to forward a request to the resource or to include the resource in a response. The resource can be dynamic or static.
How to Create an Object of RequestDispatcher?
There are three ways to get an object:
1. RequestDispatcher requestDispatcher=ServletContext.getRequestDispatcher(String path);
Description:
- public interface ServletContext. Defines a set of methods that a servlet uses to communicate with its servlet container.
- path is a string specifying the pathname to the resource(servlet, HTML file, or JSP file).
2. RequestDispatcher requestDispatcher=ServletContext.getNamedDispatcher(String name);
Description:
- public interface ServletContext. Defines a set of methods that a servlet uses to communicate with its servlet container.
- name is a string specifying the name of a servlet to wrap.
3. RequestDispatcher requestDispatcher=request.getRequestDispatcher(“String path”);
Description:
- request is the HttpServletRequest type object.
- path is a string specifying the pathname to the resource. If it is relative, it must be relative to the current servlet.
Method and Description
The class contains two methods:
1. forward
Syntax:
void forward(ServletRequest request,ServletResponse response) throws ServletException,IOException
Description:
- Modifier and Type:- void
- This method is used to forward a request from a servlet to another resource (servlet, JSP file, or HTML file) on the server.
- The method get called before the response has been sent to the client. If the response is already sent then the method will throws an IllegalStateException.
- The parameter request(HttpServletRequest type) and response(HttpServletResponse type) are the same objects as were passed to the calling servlet’s service method.
- This method sets the dispatcher type of the given request to DispatcherType.FORWARD.
Example:
Java
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;public class GFG extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) { // Perform all the work as per your // application's architecture try { RequestDispatcher requestDispatcher; // path is a string specifying the pathname to // the resource. If it is relative, it must be // relative against the current servlet requestDispatcher=request.getRequestDispatcher("path"); requestDispatcher.forward(request, response); } catch (ServletException servletException) { } catch (IOException ioException) { } catch (IllegalStateException illegalStateException) { } }} |
Note: The above code will not run in online IDE this is server-side code.
2. include
Syntax:
void include(ServletRequest request,ServletResponse response) throws ServletException,IOException
Description:
- Modifier and Type:- void
- This method is used to include the response of resource(for which the request passed servlet, JSP page, HTML file) in the current servlet response.
- The parameter request(HttpServletRequest type) and response(HttpServletResponse type) are the same objects as were passed to the calling servlet’s service method.
- This method sets the dispatcher type of the given request to DispatcherType.INCLUDE.
Example:
Java
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;public class GFG extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) { // Perform all the work as // per your application's architecture try { RequestDispatcher requestDispatcher; // path is a string specifying the pathname to // the resource. If it is relative, it must be // relative against the current servlet requestDispatcher=request.getRequestDispatcher("path"); requestDispatcher.include(request, response); } catch (ServletException servletException) { } catch (IOException ioException) { } }} |
Note: The above code will not run in online IDE this is server-side code.
Fields and Description
|
Type |
Name of Field |
Description |
|---|---|---|
| static String | FORWARD_REQUEST_URI | The string contains the name of the request attribute under which the original request URI is made available to the target of a forward. |
| static String | FORWARD_CONTEXT_PATH | The string contains the name of the request attribute under which the original context path is made available to the target of a forward. |
| static String | FORWARD_PATH_INFO | The string contains the name of the request attribute under which the original path info is made available to the target of a forward. |
| static String | FORWARD_SERVLET_PATH | The string contains the name of the request attribute under which the original servlet path is made available to the target of a forward. |
| static String | FORWARD_QUERY_STRING | The string contains the name of the request attribute under which the original query string is made available to the target of a forward. |
| static String | INCLUDE_REQUEST_URI | The string contains the name of the request attribute under which the request URI of the target of include is stored. |
| static String | INCLUDE_CONTEXT_PATH | The string contains the name of the request attribute under which the context path of the target of an include is stored. |
| static String | INCLUDE_PATH_INFO | The string contains the name of the request attribute under which the path info of the target of an include is stored. |
| static String | INCLUDE_SERVLET_PATH | The string contains the name of the request attribute under which the servlet path of the target of an include is stored. |
| static String | INCLUDE_QUERY_STRING | The string contains the name of the request attribute under which the query string of the target of an include is stored. |
| static String | ERROR_EXCEPTION | The string contains the name of the request attribute under which the exception object is propagated during an error dispatch. |
| static String | ERROR_EXCEPTION_TYPE | The string contains the name of the request attribute under which the type of the exception object is propagated during an error dispatch. |
| static String | ERROR_MESSAGE | The string contains the name of the request attribute under which the exception message is propagated during an error dispatch. |
| static String | ERROR_REQUEST_URI | The string contains the name of the request attribute under which the request URI whose processing caused the error is propagated during an error dispatch. |
| static String | ERROR_SERVLET_NAME | The string contains the name of the request attribute under which the name of the servlet in which the error occurred is propagated during an error dispatch. |
| static String | ERROR_STATUS_CODE | The string contains the name of the request attribute under which the response status is propagated during an error dispatch. |
