Solved

flush is  Invalid  for jsp:forward.. It is only valid for for jsp:include.

Posted on 2013-01-25
7
580 Views
Last Modified: 2013-02-17
I was reading as follows

The attribute flush is  Invalid  for jsp:forward.. It is only valid for for jsp:include.

I have not understood its clear meanign and where we have to use flush and how, why.

please advise.
Any links resources, sample code, ideas highly appreciated. Thanks in advance
0
Comment
Question by:gudii9
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
7 Comments
 
LVL 27

Expert Comment

by:rrz
ID: 38841262
If the flush method is called, then output is sent to the client and the response is committed. Once the response is committed, you can't forward to another resource because it needs to create it's own response. An include is allowed becauseit will only add to the current output to be sent to the client.
0
 
LVL 7

Author Comment

by:gudii9
ID: 38844719
>> An include is allowed becauseit will only add to the current output to be sent to the client.

Can you please elaborate on this.
0
 
LVL 27

Expert Comment

by:rrz
ID: 38845121
The <jsp:include> action includes the response from another JSP page, Servlet or static file in the same web application. The execution of the current page continues after including the response generated by the target resource.  If any response content has been buffered when the <jsp:include> action is executed, the flush attribute controls whether or not to flush the buffer.
0
Revamp Your Training Process

Drastically shorten your training time with WalkMe's advanced online training solution that Guides your trainees to action.

 
LVL 7

Author Comment

by:gudii9
ID: 38856159
>>If the flush method is called, then output is sent to the client and the response is committed. Once the response is committed, you can't forward to another resource because it needs to create it's own response



So for Forward order of execution of things are
1.response committed
2.output sent to client
3. flush method is called



>>>The <jsp:include> action includes the response from another JSP page, Servlet or static file in the same web application.The execution of the current page continues after including the response generated by the target resource.

In this case Target Resource means another JSP page, Servlet or static file in the same web application right?

What is the meaning of buffered. What is it relation, dependency with flush. can you please point me to any good simple example

Please advise
0
 
LVL 27

Expert Comment

by:rrz
ID: 38856734
>So for Forward order of execution of things are  
I think you are incorrect in your last comment.  
A buffer is just a storage area. Read at
http://en.wikipedia.org/wiki/Data_buffer 
When flush is called that is what sends the contents of the buffer to the client. That commits the response.  
You should read  about buffering at
http://docs.oracle.com/javaee/1.4/api/javax/servlet/jsp/JspWriter.html 

The following  JSP works  
Text here will be put into buffer. 
But when I use  the forward this text will be cleared from the buffer and will not be sent to the client. 
<jsp:forward page="test.jsp" />  

Open in new window

 The following JSP produces error
<%@ page buffer="none" %>
When no buffer is used, this text will be sent to the client.
Now, when I try to forward, An error is thrown.
<jsp:forward page="test.jsp" />  

Open in new window

The error message from trying to use last code  is
java.lang.IllegalStateException: Illegal to clear() when buffer size == 0
0
 
LVL 7

Author Comment

by:gudii9
ID: 38873390
>>>Once the response is committed, you can't forward to another resource because it needs to create it's own response.


Can forward will be able to forward to another resource in other web application?(not in the same web application)


>>>The execution of the current page continues after including the response generated by the target resource.  If any response content has been buffered when the <jsp:include> action is executed, the flush attribute controls whether or not to flush the buffer.

>>>If any response content has been buffered


response content buffered by current page or target resource?

How response still buffers even after executing <jsp:include>
please advise
0
 
LVL 27

Accepted Solution

by:
rrz earned 500 total points
ID: 38889539
>Can forward will be able to forward to another resource in other web application?(not in the same web application)  
No
>response content buffered by current page or target resource?    
current page  
>How response still buffers even after executing <jsp:include>    
The response is buffered until the end of page is reached or until the buffer overflows.
0

Featured Post

Forrester Webinar: xMatters Delivers 261% ROI

Guest speaker Dean Davison, Forrester Principal Consultant, explains how a Fortune 500 communication company using xMatters found these results: Achieved a 261% ROI, Experienced $753,280 in net present value benefits over 3 years and Reduced MTTR by 91% for tier 1 incidents.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I had a project requirement for a displaying a user workbench .This workbench would consist multiple data grids .In each grid the user will be able to see a large number of data. These data grids should allow the user to 1. Sort 2. Export the …
Introduction This article is the last of three articles that explain why and how the Experts Exchange QA Team does test automation for our web site. This article covers our test design approach and then goes through a simple test case example, how …
Viewers learn about the “for” loop and how it works in Java. By comparing it to the while loop learned before, viewers can make the transition easily. You will learn about the formatting of the for loop as we write a program that prints even numbers…
This tutorial will introduce the viewer to VisualVM for the Java platform application. This video explains an example program and covers the Overview, Monitor, and Heap Dump tabs.
Suggested Courses

759 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question