I have an issue with embedded Tomcat and classloaders.
I have a java servlet application that runs in an embedded
Tomcat(9.0.70) instance. When the application is packaged into a
single war file – the application loads and performs as expected
(classes are fond in WEB-INF/lib.
Due to some system constraints it is necessary to deliver the
application code separate from its dependencies.
I modified the application pom to copy the dependencies to
${project.build.directory}/lib/
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<version>2.5.1</version>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>package</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>${project.build.directory}/lib/</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
and to exclude the jar files from the war file
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<configuration>
<packagingExcludes>WEB-INF/lib/*.jar</packagingExcludes>
</configuration>
</plugin>
this builds the project as expected – 1 war file and one lib directory.
The class that creates the embedded Tomcat environment includes (much
abbreviated):
System.setProperty("catalina.home", catHome) ;
tomcat.start();
server = tomcat.getServer();
File base = server.getCatalinaBase();
File home = server.getCatalinaHome();
log.info("starting on port:" + sslPort +
" with home:" + home.getAbsolutePath() +
" base:" + base.getAbsolutePath());
The logging confirms that CATALINA_HOME is set.
On execution receive ClassNotFoundException,
java.lang.ClassNotFoundException:
com.google.gwt.user.server.rpc.RemoteServiceServlet
at
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1412)
at
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1220)
at java.lang.ClassLoader.defineClassImpl(Native Method)
at java.lang.ClassLoader.defineClassInternal(ClassLoader.java:396)
at java.lang.ClassLoader.defineClass(ClassLoader.java:357)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:154)
at
org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2472)
at
org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:875)
at
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1376)
at
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1220)
at
org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:534)
at
org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:515)
at
org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:149)
at
org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1067)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1007)
at
org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4948)
at
org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5256)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1393)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1383)
at java.util.concurrent.FutureTask.run(FutureTask.java:277)
at
org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
at
java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:145)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:835)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1393)
at
org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1383)
at java.util.concurrent.FutureTask.run(FutureTask.java:277)
at
org.apache.tomcat.util.threads.InlineExecutorService.execute(InlineExecutorService.java:75)
at
java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:145)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:916)
at
org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:265)
at
org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:265)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at
org.apache.catalina.core.StandardService.startInternal(StandardService.java:430)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at
org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:930)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
at org.apache.catalina.startup.Tomcat.start(Tomcat.java:486)
My understanding from
https://tomcat.apache.org/tomcat-8.0-doc/class-loader-howto.html is
that the Tomcat common loader will search for jars in
CATALINA_HOME/lib. My CATALINA_HOME/lib contains gwt-user-2.10.0.jar
which contains RemoteServiceServlet.class.
Why is the Tomcat common loader not finding this class?
many thanks
Dave Breeze
Linkedin:https://uk.linkedin.com/in/dabreeze
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