Getting a weird ClassNotDefFoundException on runtime with GWT

I am deploying a web application based on GWT. When I compile, I don't get any errors, but in runtime, I get this one (not complete stack trace):

java.lang.NoClassDefFoundError: org/xmlpull/v1/XmlPullParserException
at org.gvsig.remoteClient.sos.SOSClient.<init>(SOSClient.java:47)
at com.uji.project.server.ConnectServiceImpl.makeConnection(ConnectServiceImpl.java:18)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

Caused by:

Caused by: java.lang.ClassNotFoundException: org.xmlpull.v1.XmlPullParserException
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)

I have read on this website that that is probably caused if one or mo开发者_运维百科re classes are not available on running time but, as seen, the error is caused by some problem with the XML parser, but I have the XML parser included in my lib folder. In detail, in the project's lib folder, it is possible to find 3 JAR files: gwt-maps.jar, gwt-servlet.jar, and kxml2.jar*.

If I open "kxml2.jar" file I can see folder org that within has xmlpull folder, that within has v1 folder and finally XmlPullParserException.class.

So...why on runtime do I not have this class available if it is included on the lib folder?

In appengine classes can only access to the classesof the JRE which are in this whitelist. If this jar is using another class of the JRE it won't be included in runtime.

Here you can read that "XML processing APIs including DOM, SAX, and XSLT" are compatible with appengine. Maybe xmlpullparser is not compatible, but I'm not sure.

Finally a colleague told me the solution to this runtime error! :D

When a GWT application is deployed, many files are copied under a small file structure (pending from ) that contains all classes, libraries and other files that are needed on runtime.

For some reason, if you don't tell on purpose Eclipse to copy (on compile/deploy time) a specific library into that PATH, the application will not find on runtime that library and will raise an error.

Solution (for me) was as simple as copying by hand that library into that folder: In my case was copying "kxml2.jar" under "C:\gwt-2.1.0\SOSProject\war\WEB-INF\lib". I restarted the application and just worked. :D

I hope this patch/solution will help others to solve this annoying problem under GWT!

Try this Window->Preferences->Java Build Path->Add Jars Navigate to your project/lib, select kxml2.jar Hit OK.

In the end, what I did was to start again from the beginning: In the same workspace I had different projects and maybe there were, let's say, interferences between them.

So, I unzipped again the GWT SDK, start a new project, copied the original source code on the new project, deployed it and on runtime, now I am not getting that weird ClassNotDefFound error. Now I am getting another one, but that is another issue! Thanks to all.