Note on build systems: Gradle is nice too.
Bill
<div>-------- Original message --------</div><div>From: Joakim Erdfelt
<[email protected]> </div><div>Date:08/25/2015 6:57 AM (GMT-08:00)
</div><div>To: JETTY user mailing list <[email protected]>
</div><div>Subject: Re: [jetty-users] embedded jetty 9 JSP:
NullPointerException in org.apache.jasper.compiler.Validator </div><div>
</div>Inline comments...
On Sun, Aug 23, 2015 at 9:05 PM, Barbara Tuchman <[email protected]>
wrote:
~~~~~~~~~~ Background ~~~~~~~~~~
An application at work uses embedded jetty 6 to support a single web page that
we use to control a trading application. This was written long before I
joined, but I am stuck with maintaining it. The web page uses 4 .jsp files to
perform various actions. (The web page is actually a flash page: when you
click on certain buttons, it calls the associated .jsp to carry out the
action.) Each .jsp file is actually very simple; all are <= 1 KB in size.
I want to update the JDK on our prd server from 7 to the latest 8 release.
Testing in UAT reveals that everything works except for this web page. In
particular, with jetty 6 and JDK 8, I see this error in the logs:
2015-08-21T17:19:26.183-0400 WARN [qtp0-0] - Compilation error
org.eclipse.jdt.internal.compiler.classfmt.ClassFormatException: null
at
org.eclipse.jdt.internal.compiler.classfmt.ClassFileReader.<init>(ClassFileReader.java:298)
~[core-3.1.1.jar:na]
at
org.apache.jasper.compiler.JDTJavaCompiler$1.findType(JDTJavaCompiler.java:351)
~[jsp-2.1.jar:6.1.11]
...
Clearly, the ancient jdt compiler in jetty 6 cannot handle JDK 8 class files.
So, it is time to upgrade to a modern jetty version.
Unfortunately, when I try jetty 9, I get a NullPointerException in
org.apache.jasper.compiler.Validator. I cannot figure out why. The rest of
this email provides details.
Per the JSP spec the Java support level is Java 6 (and it still is, even today).
Notice that Jetty 6 doesn't use Java itself to compile JSPs?
Jetty 6 is using the Eclipse JDT compiler.
Breaking spec to support Java 8 is handled by configuring to use Java and JavaC
itself.
~~~~~~~~~~ Step 1 ~~~~~~~~~~
The first issue that I was faced with in upgrading to a modern jetty is
determining what jar files I need. This is actually a nightmare, because:
1) jetty 9 seems to have ~50 jars of its own, plus dependencies on ~50 more
(see Step 3 below for proof)
2) our project does not use maven or ant (just IntelliJ, as our project is
fairly simple in regards to build requirements), and jetty seems to really want
maven
Jetty is a 100% modular web container.
Nothing is mandatory. (Not even the Server!)
There is no concept of "all", "minimum", or "everything". (these mean different
things to different people).
You really should use some sort of build system.
You have many to choose from.
Would recommend: Apache Maven, Grails, or Apache Ant+Ivy.
Alternative build tooling: Apache Buildr, Groovy Grape, Scala SBT, or Leiningen
IntelliJ supports Apache Maven and Grails *very well*.
Once you decide what you need, you reference just that, and let the build
tooling pull in what's relevant. (eg: you want jsp, so you use
"org.eclipse.jetty:apache-jsp:{jetty-version}", and you'll wind up with the
jars that you need, resolved for conflicts and build/compile vs test scopes)
I came across this web page
https://www.eclipse.org/jetty/documentation/current/advanced-embedding.html
which mentions using a "jetty-all.jar" file to work around this problem. So, I
downloaded the latest stable one
jetty-all-9.3.2.v20150730-uber.jar
I had to change some of my embedded code that launches the jetty server (e.g.
to cope with new package names, slightly different API), but this was fairly
straight forward.
Unfortunately, running my code failed: I see console logs like this:
2015-08-21T16:50:48.165-0400 INFO [qtp889486595-18] {/} - No JSP support.
Check that JSP jars are in lib/jsp and that the JSP option has been specified
to start.jar
(That log level probably ought to be ERROR, not INFO?)
You should not use jetty-all.jar.
Something we use to help people understand jetty in our documentation. (and
limited in scope to support only this task)
It's not meant to be used from any real world project.
~~~~~~~~~~ Step 2 ~~~~~~~~~~
A web search found a similar issue described here:
https://stackoverflow.com/questions/26217143/embedded-jetty-server-no-jsp-support-for-did-not-find-org-apache-jasper-ser
Looks like the "all uber" jar file does not contain everything after all,
contrary to its name. In the link above, Joakim Erdfelt eventually comments
that
"jetty-all.jar only exists as a teaching aid (referenced in the
documentation), its not meant for production use"
Given that tip, since I had already downloaded a copy of the full
9.3.2.v20150730 distribution, I tried copying these additional 4 jars
org.eclipse.jetty.apache-jsp-9.3.2.v20150730.jar
org.eclipse.jetty.orbit.org.eclipse.jdt.core-3.8.2.v20130121.jar
org.mortbay.jasper.apache-el-8.0.23.M1.jar
org.mortbay.jasper.apache-jsp-8.0.23.M1.jar
from its lib/apache-jsp directory into my project's lib directory (where all
its jar files live).
Running my code with these 4 additional jars now fails further on: I see this
log:
2015-08-21T16:54:30.933-0400 WARN [qtp1238959340-38] -
org.apache.jasper.JasperException: Unable to compile class for JSP
at
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:600)
~[org.mortbay.jasper.apache-jsp-8.0.23.M1.jar:2.3]
at
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:363)
~[org.mortbay.jasper.apache-jsp-8.0.23.M1.jar:2.3]
...
Caused by: java.lang.NullPointerException: null
at
org.apache.jasper.compiler.Validator$ValidateVisitor.<init>(Validator.java:515)
~[org.mortbay.jasper.apache-jsp-8.0.23.M1.jar:2.3]
at
org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1853)
~[org.mortbay.jasper.apache-jsp-8.0.23.M1.jar:2.3]
...
Indiscriminate copying of jar files is not going to help you.
Did you know that those 4 jar files provide you JSP (no JSTL) and will operate
in the JSP spec/standard mode of Java 6? Just like Jetty 6.
Again, use Maven (or Grails) to obtain the correct jars, and then configure
your desired environment correctly for Java 8 support.
~~~~~~~~~~ Step 3 ~~~~~~~~~~
I got tired of guessing what jars my app needs, and decided on a simple brute
force way to pull down everything:
1) I deleted the 5 jetty jars described above from my app's lib directory
2) I completely emptied my C:\Users\Sam\.m2\repository directory
3) I downloaded the Embedded Jetty w/ JSP Support project
https://github.com/jetty-project/embedded-jetty-jsp
4) I built it (mvn clean package), started the server (mvn exec:exec), and
verified that it worked in my browser (http://localhost:8080/)
5) I copied every *.jar file from my C:\Users\Sam\.m2\repository directory
(there are 100 of them!) into my app's lib directory
Step #5 is completely the wrong thing to do.
You now have many duplicate classes, from different versions of the same
artifact.
You also now have many classes that are actually dangerous (from a security
point of view) to run in production.
You also have all of the maven infrastructure (and 3rd party plugins) in your
web server now.
Use Maven (or Grails) to get the appropriate set of jars that you need.
Running my code with these 100 jetty jars fails with a similar stack trace:
2015-08-21T16:03:52.001-0400 WARN [qtp934275857-19] -
org.apache.jasper.JasperException: Unable to compile class for JSP
at
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:579)
~[apache-jsp-8.0.9.M3.jar:2.3]
at
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
~[apache-jsp-8.0.9.M3.jar:2.3]
...
Caused by: java.lang.NullPointerException: null
at
org.apache.jasper.compiler.Validator$ValidateVisitor.<init>(Validator.java:515)
~[apache-jsp-8.0.9.M3.jar:2.3]
at
org.apache.jasper.compiler.Validator.validateExDirectives(Validator.java:1846)
~[apache-jsp-8.0.9.M3.jar:2.3]
...
This is probably essentially the same as Step 2 above: recall that Step 2 used
jetty 9.3.2.v20150730, whereas the Embedded Jetty w/ JSP Support project still
uses jetty-9.2.6. So, that likely explains the different line numbers in the
stack traces.
You are still using the JSP spec mandated Java 6 support.
The Eclipse JDT compiler is still in use.
Switch to using JavaC.
~~~~~~~~~~ Future work ~~~~~~~~~~
My conclusion after Step 3 is that I cannot be missing something on my
classpath at this point.
Doing a more focused web search found:
--this link, which reports what looks like the same problem (but has no
solution):
http://jspl598.blogspot.com/2015/03/while-accessing-jsps-in-jetty_13.html
This looks like your blog.
Its identical to what you are describing.
Why they didn't use this forum, or stackoverflow, i cannot comprehend.
--this link, which reports what looks like the same problem, claims to have
a solution, but hides it behind subscription access:
https://access.redhat.com/solutions/315013
This one isn't related to your problem.
This is a configuration issue in jboss.
--this link, which reports what looks like the same problem, and whose
solution was to correct a typo in a .tld file:
http://www.coderanch.com/t/614308/JSP/java/EL-function
This one was a mistake in their tld definition.
Once fixed, it started to work for them.
The solution in that final link above suggests that there is some bug in my
code.
I do not have any .tld files, so the precise solution there is not relevant for
me.
I quickly inspected my .jsp files, and see nothing obviously wrong.
Furthermore, I note that the .jsp files all worked under jetty 6.
SO, DOES ANYONE HAVE ANY SUGGESTIONS FOR WHERE I CAN LOOK TO DEBUG THIS?
Most important recommendations:
Don't flail.
Understand the problem.
Use Maven (or grails) to get the correct set of Jars that *you* need for your
project.
Don't include the eclipse jdt jar in your project (use exclusions with
maven/grails)
Look at the code for github.com/jetty-project/embedded-jetty-jsp
Configure for JavaC
Setup context Attributes
Setup InstanceManager
Setup JettyJasperInitializer
(and more, see the code)
Good luck,
- Joakim_______________________________________________
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