Chapter 34. Extensibility - CloverDX Engine Plugins

Since 3.1.2

The CloverDX Server can use external engine plugins loaded from a specified source. The source is specified by engine.plugins.additional.src config property.

See details about the possibilities with CloverDX configuration in Part III, “Configuration”

This property must be the absolute path to the directory or zip file with additional CloverDX engine plugins. Both the directory and zip file must contain a subdirectory for each plugin. These plugins are not a substitute for plugins packed in a WAR file. Changes in the directory or the ZIP file apply only when the Server is restarted.

Each plugin has its own class-loader that uses a parent-first strategy by default. The parent of plugins' classloaders is web-app classloader (content of [WAR]/WEB-INF/lib). If the plugin uses any third-party libraries, there may be some conflict with libraries on the parent-classloaders classpath. These are common exceptions/errors suggesting that there is something wrong with classloading:

There are sevral ways you can get rid of such conflicts:

The suggestions above may be combined. Finding the best solution for these conflicts may depend on the libraries on app-server classpath.

For more convenient debugging, it is useful to set a TRACE log level for related class-loaders.

<logger name="org.jetel.util.classloader.GreedyURLClassLoader">
        <level value="trace"/>
</logger>
<logger name="org.jetel.plugin.PluginClassLoader">
        <level value="trace"/>
</logger>

See Chapter 17, Logging for details about overriding a server log4j configuration.