How to set java endorsed dir for tomcat7-maven-plugin
Sometimes you need to use Java endorsed standards override mechanism with Maven plugins. This can be accomplished simply by setting proper MAVEN_OPTS value. For exampleexport MAVEN_OPTS="-Djava.endorsed.dirs=/some/directory/where/endorsed/jars/are"
How to change tomcat7-maven-plugin classpath order
Very often you need to have the runtime classpath in certain order when running Tomcat or other Maven plugins. I found out by trial and error that the used classpath JAR ordering depends on the order of declared dependencies in pom.xml (most likely this is documented somewhere). So, if you need to get some libraries before others, just move them in the beginning of pom.xml. Of course this does not help, if you have many plugins that need a different order for each plugin.
How to list all loaded classes and their respective JAR files
This is something I had been looking for years and was extremely happy when I finally got to know it. At least Sun Java JRE provides a command line switch for showing all the classes that are loaded into JVM and the source JAR file of those classes. It's not always easy to know what classes are loaded, especially if your dependencies have dependencies to other JAR files that are somehow conflicting (for example different version) with JAR dependencies defined elsewhere. Anyway, to list the classes and their exact source, do the following.
export MAVEN_OPTS="-verbose:class"
The output is something like this.
[Loaded javax.xml.bind.annotation.XmlElement from /home/perttu/software/jdks/jdk1.6.0_31/jre/lib/rt.jar] [Loaded javax.xml.bind.annotation.XmlElement$DEFAULT from /home/perttu/software/jdks/jdk1.6.0_31/jre/lib/rt.jar] [Loaded javax.xml.ws.WebFault from /home/perttu/software/jdks/jdk1.6.0_31/jre/lib/rt.jar]
With these tools, any problem related to Tomcat Maven plugin and classpath should be easy to solve.
