Package org.apache.nutch.plugin

package org.apache.nutch.plugin

The Nutch Plugin System.

The Nutch Plugin System provides a way to extend nutch functionality. A large part of the functionality of Nutch are provided by plugins: All of the parsing, indexing and searching that nutch does is actually accomplished by various plugins.

In writing a plugin, you're actually providing one or more extensions of the existing extension-points (hooks). The core Nutch extension-points are themselves defined in a plugin, the nutch-extensionpoints plugin. Each extension-point defines an interface that must be implemented by the extension. The core extension-points and extensions available in Nutch are listed in the Pluggable interface.

See Also:

• Nutch plugin manifest DTD
• Plugin Central
• About Plugins
• Why Nutch has a Plugin System?
• Which technical concepts are behind the nutch plugin system?
• What's the problem with Plugins and Class loading?
• Writing Plugin Example

Class	Description
CircularDependencyException	CircularDependencyException will be thrown if a circular dependency is detected.
Extension	An Extension is a kind of listener descriptor that will be installed on a concrete ExtensionPoint that acts as kind of Publisher.
ExtensionPoint	The ExtensionPoint provide meta information of a extension point.
MissingDependencyException	MissingDependencyException will be thrown if a plugin dependency cannot be found.
Pluggable	Defines the capability of a class to be plugged into Nutch.
Plugin	A nutch-plugin is an container for a set of custom logic that provide extensions to the nutch core functionality or another plugin that provides an API for extending.
PluginClassLoader	The PluginClassLoader is a child-first classloader that only contains classes of the runtime libraries setuped in the plugin manifest file and exported libraries of plugins that are required plugins.
PluginDescriptor	The PluginDescriptor provide access to all meta information of a nutch-plugin, as well to the internationalizable resources and the plugin own classloader.
PluginManifestParser	The PluginManifestParser provides a mechanism for parsing Nutch plugin manifest files (plugin.xml) contained in a String of plugin directories.
PluginRepository	The plugin repository is a registry of all plugins.
PluginRuntimeException	PluginRuntimeException will be thrown until a exception in the plugin managemnt occurs.
URLStreamHandlerFactory	This URLStreamHandlerFactory knows about all the plugins in use and thus can create the correct URLStreamHandler even if it comes from a plugin classpath.