org.apache.nutch.plugin

Class PluginRepository

java.lang.Object

org.apache.nutch.plugin.PluginRepository

public class PluginRepository
extends Object

The plugin repositority is a registry of all plugins. At system boot up a repositority is builded by parsing the mainifest files of all plugins. Plugins that require not existing other plugins are not registed. For each plugin a plugin descriptor instance will be created. The descriptor represents all meta information about a plugin. So a plugin instance will be created later when it is required, this allow lazy plugin loading.

Field Summary

Fields

Modifier and Type	Field and Description
static org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor and Description
PluginRepository(org.apache.hadoop.conf.Configuration conf)

Method Summary

Methods

Modifier and Type	Method and Description
void	finalize()
static PluginRepository	get(org.apache.hadoop.conf.Configuration conf)
Class	getCachedClass(PluginDescriptor pDescriptor, String className)
ExtensionPoint	getExtensionPoint(String pXpId) Returns a extension point indentified by a extension point id.
Object[]	getOrderedPlugins(Class<?> clazz, String xPointId, String orderProperty) Get ordered list of plugins.
PluginDescriptor	getPluginDescriptor(String pPluginId) Returns the descriptor of one plugin identified by a plugin id.
PluginDescriptor[]	getPluginDescriptors() Returns all registed plugin descriptors.
Plugin	getPluginInstance(PluginDescriptor pDescriptor) Returns a instance of a plugin.
static void	main(String[] args) Loads all necessary dependencies for a selected plugin, and then runs one of the classes' main() method.

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

LOG

public static final org.slf4j.Logger LOG

Constructor Detail

PluginRepository

public PluginRepository(org.apache.hadoop.conf.Configuration conf)
                 throws RuntimeException

Throws:

PluginRuntimeException

RuntimeException

See Also:

Object.Object()

Method Detail

get

public static PluginRepository get(org.apache.hadoop.conf.Configuration conf)

Returns:

a cached instance of the plugin repository

getPluginDescriptors

public PluginDescriptor[] getPluginDescriptors()

Returns all registed plugin descriptors.

Returns:

PluginDescriptor[]

getPluginDescriptor

public PluginDescriptor getPluginDescriptor(String pPluginId)

Returns the descriptor of one plugin identified by a plugin id.

Parameters:

pPluginId -

Returns:

PluginDescriptor

getExtensionPoint

public ExtensionPoint getExtensionPoint(String pXpId)

Returns a extension point indentified by a extension point id.

Parameters:

pXpId -

Returns:

a extentsion point

getPluginInstance

public Plugin getPluginInstance(PluginDescriptor pDescriptor)
                         throws PluginRuntimeException

Returns a instance of a plugin. Plugin instances are cached. So a plugin exist only as one instance. This allow a central management of plugin own resources. After creating the plugin instance the startUp() method is invoked. The plugin use a own classloader that is used as well by all instance of extensions of the same plugin. This class loader use all exported libraries from the dependend plugins and all plugin libraries.

Parameters:

pDescriptor -

Returns:

Plugin

Throws:

PluginRuntimeException

finalize

public void finalize()
              throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable

getCachedClass

public Class getCachedClass(PluginDescriptor pDescriptor,
                   String className)
                     throws ClassNotFoundException

Throws:

ClassNotFoundException

getOrderedPlugins

public Object[] getOrderedPlugins(Class<?> clazz,
                         String xPointId,
                         String orderProperty)

Get ordered list of plugins. Filter and normalization plugins are applied in a configurable "pipeline" order, e.g., if one plugin depends on the output of another plugin. This method loads the plugins in the order defined by orderProperty. If orderProperty is empty or unset, all active plugins of the given interface and extension point are loaded.

Parameters:

clazz - interface class implemented by required plugins

xPointId - extension point id of required plugins

orderProperty - property name defining plugin order

Returns:

array of plugin instances

main

public static void main(String[] args)
                 throws Exception

Loads all necessary dependencies for a selected plugin, and then runs one of the classes' main() method.

Parameters:

args - plugin ID (needs to be activated in the configuration), and the class name. The rest of arguments is passed to the main method of the selected class.

Throws:

Exception