Troubleshooting and FAQ

Troubleshooting and FAQ

Installation Issues

Maven keeps downloading things over and over again. This is annoying. What can I do?

Use mvn -o if you are using Maven on the command line.

Given you are using the m2eclipse plugin in Eclipse, create a new Maven Run Configuration (or use an existing one) and click the “Offline” checkbox.

mvn gwt:gwt Reports Missing libstdc++ Library

If you encounter an error looking like this:

	[INFO] google.webtoolkit.home (gwtHome) set, using it for GWT dependencies - /home/my.myself.i/werti-dl/gwt-linux-1.5.2
	** Unable to load Mozilla for hosted mode **
	java.lang.UnsatisfiedLinkError: /home/me.myself.i/werti-dl/gwt-linux-1.5.2/mozilla-1.7.12/libxpcom.so: libstdc++.so.5: cannot open shared object file: No such file or directory
	        at java.lang.ClassLoader$NativeLibrary.load(Native Method)
	       	at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1751)
	        at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1647)
	        at java.lang.Runtime.load0(Runtime.java:769)
	        at java.lang.System.load(System.java:968)
	        at com.google.gwt.dev.shell.moz.MozillaInstall.load(MozillaInstall.java:190)
	        at com.google.gwt.dev.BootStrapPlatform.init(BootStrapPlatform.java:49)
	        at com.google.gwt.dev.GWTShell.main(GWTShell.java:354)

This means that on your system you are missing the old version of libstdc, which is needed by the
Google Web Toolkit. Use the package manager of your system and search for libstdc++ and
install version 5 of this library. The package name in Ubuntu/Debian is libstdc++5.

Something (like Maven or Tomcat) complains about “Unsupported major.minor version yy.xx”

This is caused by the mixed use of different versions of Java. For example, if a class file has been built with Java 1.6, it cannot be run with Java 1.5. WERTi is currently being developed with Java 1.5, so it is a good idea to install the corresponding JDK and to set the JAVA_HOME environment variable to point to the location of the installation before running Maven or Tomcat.

Be aware that Eclipse usually manages these things in a different way: The Java Compiler page in the project properties can be used to adjust the Java version. Furthermore, one should have the corresponding Java system library in the buildpath.
It is a good idea to adjust this setting in the Preferences dialog (Window --- Preferences) for the entire Workspace, as the many places where one can chose a JDK usually default to the Workspace setting.