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Posted to dev@tomcat.apache.org by bu...@apache.org on 2019/10/31 21:10:28 UTC

[Bug 63897] New: Jasper doesn't reload a JSP if it was modified while being compiled

https://bz.apache.org/bugzilla/show_bug.cgi?id=63897

            Bug ID: 63897
           Summary: Jasper doesn't reload a JSP if it was modified while
                    being compiled
           Product: Tomcat 9
           Version: 9.0.27
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Jasper
          Assignee: dev@tomcat.apache.org
          Reporter: karl@xk72.com
  Target Milestone: -----

Created attachment 36867
  --> https://bz.apache.org/bugzilla/attachment.cgi?id=36867&action=edit
Compiler patch

In our development workflow we often save a JSP and reload it in the browser,
again and again. If we happen to save a JSP while Jasper is compiling it,
Jasper will assign the timestamp of the modified JSP to the generated java and
class files even though they were in fact generated from the previous version
of the JSP, as Jasper reads the JSP's modification time _after_ compiling.
Jasper will then not detect that the change was made and will not recompile the
JSP again until the next time it is modified.

The fix is to simply move the line of code in
org.apache.jasper.compiler.Compiler in the compile(boolean, boolean) method
that reads the jspLastModified from after the compile to before it.

This change will mean no missed JSP updates.

A simple patch is attached.

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[Bug 63897] Jasper doesn't reload a JSP if it was modified while being compiled

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=63897

Christopher Schultz <ch...@christopherschultz.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |PatchAvailable

--- Comment #1 from Christopher Schultz <ch...@christopherschultz.net> ---
Many thanks for your analysis and your patch.

Based solely upon the description and not having read the code, I tend to agree
that the timestamp used for comparison against the source JSP needs to be the
timestamp of the source JSP as it was being initially read for compilation.

I think the only place that is stored is in the timestamp of the generated
.java/.class files themselves, and there is not any other repository of that
metadata. Some filesystems (any modern ones?) don't have great time-resolution
and that may also be a contributing factor.

As this is a bit of an edge case -- nobody should be modifying JSP files at
high-frequency in production -- I don't think it makes sense to consider any
separate repository of such metadata.

(I can say for sure that I've had timing issues with Tomcat for years that are
similar to this -- usually with regard to reloading the whole container -- and
I wonder if this bug is representative of a class of problems like this.)

This patch LGTM, but I want to let others weigh-in just in case there is some
specific reasoning behind the timing of the file-timestamp-capture.

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[Bug 63897] Jasper doesn't recompile a JSP if it was modified while being compiled

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=63897

Mark Thomas <ma...@apache.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #2 from Mark Thomas <ma...@apache.org> ---
Patch looks good to me. Many thanks.

Fixed in:
- master for 9.0.28 onwards
- 8.5.x for 8.5.48 onwards
- 7.0.x for 7.0.98 onwards

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[Bug 63897] Jasper doesn't recompile a JSP if it was modified while being compiled

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=63897

Karl von Randow <ka...@xk72.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Jasper doesn't reload a JSP |Jasper doesn't recompile a
                   |if it was modified while    |JSP if it was modified
                   |being compiled              |while being compiled

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[Bug 63897] Jasper doesn't recompile a JSP if it was modified while being compiled

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=63897

--- Comment #3 from Karl von Randow <ka...@xk72.com> ---
Thank you very much. Love your work.

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