ClassLoaders

A separate class loader is used to load the classes of each plugin. This allows each plugin to use a different library version, even if the same library is used by the IDE itself or by another plugin.

By default, the main IDE class loader loads classes that are not found in the plugin class loader. However, in the plugin.xml file, you may use the <depends> element to specify that a plugin depends on one or more other plugins. In this case, the class loaders of those plugins will be used for classes not found in the current plugin. This allows a plugin to reference classes from other plugins.

Using ServiceLoader

Some libraries use ServiceLoader to detect and load implementations. For this to work in a plugin, the context class loader must be set to the plugin's classloader and restored afterwards with original one around initialization code:

    ClassLoader current = Thread.currentThread().getContextClassLoader();
    try {
        Thread.currentThread().setContextClassLoader(this.getClass().getClassLoader());
        // code working with ServiceLoader here
    } finally {
        Thread.currentThread().setContextClassLoader(current);
    }