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Clarifications for Using Methods

76 iPlanet Web Server, Enterprise Edition Programmer’s Guide to Servlets • May 2001

RequestDispatcher.forward and include

public void forward(ServletRequest request, ServletResponse

response) throws ServletException, IOException;

Used for forwarding a request from this servlet to another resource on the web

server. This method is useful when one servlet does preliminary processing of a

request and wants to let another object generate the response.

The request object passed to the target object will have its request URL path and

other path parameters adjusted to reflect the target URL path of the target object.

You cannot use this method if a

ServletOutputStream object or PrintWriter

object has been obtained from the response. In that case, the method throws an

IllegalStateException.

public void include(ServletRequest request, ServletResponse

response) throws ServletException, IOException;

Used for including the content generated by another server resource in the body of

a response. In essence, this method enables programmatic server-side includes. The

request object passed to the target object reflects the request URL path and path

info of the calling request. The response object only has access to the calling

servlet’s

ServletOutputStream object or PrintWriter object.

An included servlet cannot set headers. If the included servlet calls a method that

needs to set headers (such as

cookies), it will not work. As a servlet developer, you

must ensure that any methods that might need direct access to headers are

properly resolved. To ensure that a session works correctly, start the session

outside the included servlet, even if you use session tracking.

Clarification

In iPlanet Web Server 6.0, the dispatcher.forward method may or may not throw

IllegalStateException when either Writer or OutputStream have been

obtained. This behavior follows the 2.2 draft and is needed for JSP error page

handling. It throws the exception only if the actual data has been flushed out and

sent to the client. Otherwise, the data pending in the buffer is simply discarded.

The

forward and include methods may throw a ServletException if the target

URI is identified as an unsafe URI (that is, it includes insecure path characters such

//, /./, /../ and/., /.. (and also ./ for NT) at the end of the URI.

You can control the nesting depth of the

RequestDispatcher.forward and

include methods using the requestDispatcherNestDepth parameter in

magnus.conf. For more information, see Appendix A, “Servlet Settings in

magnus.conf and obj.conf.”

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Red Hat NETSCAPE ENTERPRISE SERVER 6.0 - NSAPI PROGRAMMER GUIDE Manuale Utente Pagina 76

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