Problems with classpath with JSP using maven exec:java plugin under Windows

Question

I'm trying to run a Jetty web framework from main(...) that loads a spring web context which loads JSPs at runtime. This works great from the command line using mvn exec:java on OSX and Linux. However on Windows, running Cygwin, I cannot get it to fully work.

The application loads and the web-context seems to build fine. However when the first JSP page is rendered the JVM goes to compile it on the fly and throws the following error/exception:

org.apache.tools.ant.BuildException: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK
    at org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.getCompiler(CompilerAdapterFactory.java:105) ~[gwt-dev-2.5.1.jar:na]
    at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:924) ~[gwt-dev-2.5.1.jar:na]
    at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:757) ~[gwt-dev-2.5.1.jar:na]
    at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:382) [gwt-dev-2.5.1.jar:na]
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:472) [gwt-dev-2.5.1.jar:na]
    ...

I've done a ton of web searches and tried a number of things before posting.

The JAVA_HOME variable is set correctly.
I've made sure that it is pointing at the JDK and not the JRE. The tools.jar file does exist under %JAVA_HOME%/lib/tools.jar.
The JAVA_HOME path is in Program Files and I was worried about the space but replacing it with Progra~1 does not seem to work either.
We've tried both the mvn shell script under Cygwin as well as the mvn.bat script under DOS but both fail similarly.

Anyone else had this problem? Do I need to change the classpath to specifically add a dependency to the tools.jar somehow? Maybe something added to the pom.xml? Thanks in advance.

What version of maven are you working with? Have you looked into the source code of [ant](http://grepcode.com/file/repository.springsource.com/org.apache.ant/com.springsource.org.apache.tools.ant/1.8.1/org/apache/tools/ant/taskdefs/compilers/CompilerAdapterFactory.java#CompilerAdapterFactory.getCompiler%28java.lang.String%2Corg.apache.tools.ant.Task%29)? — Sotirios Delimanolis, Feb 18 '14 at 19:39
I'm using maven 2.2.1 and I'm not using ant @SotiriosDelimanolis. — Gray, Feb 18 '14 at 22:51
Whatever is producing your log seems to be using ant, I just assumed it was maven. With an older version, is it possible that there's no support for a Java 7 (if that's what you are using) compiler. — Sotirios Delimanolis, Feb 18 '14 at 23:00
Duh, right. I wonder if I'm pulling some crap from gwt-dev that I shouldn't be @SotiriosDelimanolis. Thanks for poking me to actually look at all of the paths. — Gray, Feb 18 '14 at 23:20

score 0 · Accepted Answer · edited May 23 '17 at 11:49

com.sun.tools.javac.Main is not on the classpath.

I'm not sure this is the right solution but I found a workaround from this answer:

Using javah maven-antrun-plugin with jdk 1.7, classes.jar became tools.jar

I also utilized this answer: JDK tools.jar as maven dependency

I ended up adding a specific dependency for Windows in the pom which added the tools.jar specifically to the classpath:

<profiles>
    <profile>
        <id>windows</id>
        <activation>
            <activeByDefault>false</activeByDefault>
            <os>
                <family>windows</family>
            </os>
        </activation>
        <dependencies>
            <dependency>
                <groupId>com.sun</groupId>
                <artifactId>tools</artifactId>
                <version>1.6</version>
                <scope>system</scope>
                <systemPath>${java.home}/../lib/tools.jar</systemPath>
            </dependency>
        </dependencies>
    </profile>
</profiles>

This adds a dependency only if the OS family is windows. The system-path ../ is necessary in the path because ${java.home} ends up as $JAVA_HOME/jre for some reason. The version didn't seem to matter since 1.7 and 1.6 seemed to work.

Hope this helps other folks.

Problems with classpath with JSP using maven exec:java plugin under Windows

1 Answers1