View source for FAQ What causes my plug-in to build but not to load in a runtime workbench?

Runtime problems are usually indicated by a <code>java.lang.NoClassDefFoundError</code> when the plug-in is started.

To troubleshoot runtime issues, it is helpful to understand a little bit more about Eclipse classpaths.
Eclipse distinguishes between a compile-time classpath and a runtime classpath. The compile-time classpath provides the Eclipse development workbench with all necessary information for compiling a plug-in and is declared in the plug-in project's <code>.classpath</code> file. The runtime classpath, on the other hand, tells OSGi and the Eclipse runtime workbench which plug-ins and JARs are necessary to execute the plug-in. The runtime classpath is determined by the <code>MANIFEST.MF</code> file. Typically, the compile-time classpath includes most runtime dependencies, and the recommended way to incorporate these dependencies also at compile-time is to use the '''Plug-in Dependencies''' classpath container. This container will be automatically populated with the dependencies listed in the <code>MANIFEST.MF</code> file.

<code>java.lang.NoClassDefFoundError</code>s are runtime problems, so editing the <code>.classpath</code> file will usually not solve these problems. Instead, check these files:

* the <code>MANIFEST.MF</code> file
* the <code>build.properties</code> file
* the launch configuration that you used to start the plug-in

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In most cases, the <code>MANIFEST.MF</code> is the culprit. The most common problems with the manifest are:

* missing "<code>.</code>" entry in the <code>Bundle-ClassPath</code>, especially when additional JARs were added to the plug-in's runtime classpath
* missing <code>Export-Package</code> in the manifest of required plug-ins

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Next in line of the trouble-makers is the <code>build.properties</code> file. Most developers consider the <code>build.properties</code> file a compile-time file, because it mainly tells the PDE build how to package a deployable plug-in. However, the <code>build.properties</code> file is also used by PDE to create a runtime workbench that (as closely as possible) replicates the behavior that one would see if the packaged plug-in were to be deployed into a primary workbench. This "black magic" behind the scenes may preclude certain JARs or packages from being visible at runtime if the <code>build.properties</code> file is incorrect or incomplete. If you are 100% sure that your manifest is absolutely correct then you should check for warning markers in the <code>build.properties</code> file.

Finally, if your plug-in (or another plug-in that is required by your plug-in) is not enabled as part of your launch configuration its classes obviously cannot be loaded at runtime. If your launch configuration uses the "plug-ins selected below only" option, make sure that all required plug-ins are indeed selected in the list.


== See Also: ==


[[FAQ_How_do_I_add_an_extra_library_to_my_project%26%23146%3Bs_classpath%3F]]


[[FAQ_My_runtime_workbench_runs%2C_but_my_plug-in_does_not_show._Why%3F]]


[[FAQ_When_does_PDE_change_a_plug-in%26%23146%3Bs_Java_build_path%3F]]

<hr><font size=-2>This FAQ was originally published in [http://www.eclipsefaq.org Official Eclipse 3.0 FAQs]. Copyright 2004, Pearson Education, Inc. All rights reserved. This text is made available here under the terms of the [http://www.eclipse.org/legal/epl-v10.html Eclipse Public License v1.0].</font>