Tree of RequestDispatcher.forward()

Question

Suppose I am running a JSP/Servlet driven website. A user POSTs data to the root directory and I have a servlet (Index.java) that handles the path /. What I want this servlet to do is look at some of the data in the request and determine which of a second level of servlets should handle it. When it decides which second level servlet will handle the request, it forward()s to that second level servlet.

Now my problem is, what happens if a third level of servlet is needed? The second level of servlets cannot forward() to the third level because the dispatcher claims the response has already been committed.

Visually:

Index.java
 +SecondLevelA.java
 +SecondLevelB.java
 \SecondLevelC.java
   \ThirdLevelC.java

The SecondLevelC.java cannot forward to the third level. I also cannot redirect because I will lose the POST prameters in the redirect. POST is required because the data is too large for a GET query.

Consider refactoring your architecture altogether. An MVC approach might work better. — Sotirios Delimanolis, Feb 22 '14 at 03:11
Request dispatching is not limited by 'levels' or number of forwards. If the response was committed, something else in your code caused that. — helderdarocha, Feb 22 '14 at 03:18

score 1 · Accepted Answer · edited May 23 '17 at 10:31

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The RequestDispatcher.forward() has nothing to do with the levels. It can be called any number of time hierarchically. The only condition is before any RequestDispatcher.forward() is called, the response should not be committed. It's true for first invocation as well.

In your case its most probably the first child servlet is causing the response to be committed.

Here are the reasons for response getting committed:

Causes of Response getting committed.

edited May 23 '17 at 10:31

Community

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answered Feb 22 '14 at 04:04

Ramesh PVK

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The odd thing that I was seeing in the debugger was that before the RequestDispatcher.forward() call, the 'appCommitted' variable was false, but afterwards it was true. I ended up working around the problem so I no longer have example code to replicate this, however. There must have been something about the next level servlet that committed the response, but I have no idea what as it was an empty servlet. – Huckle Feb 24 '14 at 21:26
Yes , usally when you are writing the response and the max buffer size is reached. The server will commit the response. – Ramesh PVK Feb 24 '14 at 22:15

Tree of RequestDispatcher.forward()

1 Answers1