[TOC]

org.apache.nutch.plugin

Class 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.

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Methods inherited from class java.lang.Object

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

Field Detail

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LOG

public static final org.slf4j.Logger LOG

Constructor Detail

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PluginRepository

public PluginRepository(org.apache.hadoop.conf.Configuration conf)
                 throws RuntimeException
  - Throws: 
  - <code>PluginRuntimeException</code> 
  - <code>RuntimeException</code>
  - See Also:
  - [<code>Object.Object()</code>](http://java.sun.com/javase/6/docs/api/java/lang/Object.html?is-external=true#Object())

Method Detail

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get

public static PluginRepository get(org.apache.hadoop.conf.Configuration conf)
  - Returns:
  - a cached instance of the plugin repository       
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getPluginDescriptors

public PluginDescriptor[] getPluginDescriptors()

Returns all registed plugin descriptors.

  - Returns:
  - PluginDescriptor[]       
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getPluginDescriptor

public PluginDescriptor getPluginDescriptor(String pPluginId)

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

  - Parameters:
  - <code>pPluginId</code> -  
  - Returns:
  - PluginDescriptor       
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getExtensionPoint

public ExtensionPoint getExtensionPoint(String pXpId)

Returns a extension point indentified by a extension point id.

  - Parameters:
  - <code>pXpId</code> -  
  - Returns:
  - a extentsion point       
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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:
  - <code>pDescriptor</code> -  
  - Returns:
  - Plugin 
  - Throws: 
  - <code>PluginRuntimeException</code>       
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finalize

public void finalize()
              throws Throwable
  - Overrides: 
  - <code>finalize</code> in class <code>Object</code> 
  - Throws: 
  - <code>Throwable</code>       
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getCachedClass

public Class getCachedClass(PluginDescriptor pDescriptor,
                   String className)
                     throws ClassNotFoundException
  - Throws: 
  - <code>ClassNotFoundException</code>       
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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:
  - <code>clazz</code> - interface class implemented by required plugins
  - <code>xPointId</code> - extension point id of required plugins
  - <code>orderProperty</code> - property name defining plugin order 
  - Returns:
  - array of plugin instances       
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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:
  - <code>args</code> - 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: 
  - <code>Exception</code>

Copyright © 2014 The Apache Software Foundation