Package org.datanucleus.plugin

Interface PluginRegistry

All Known Implementing Classes:

NonManagedPluginRegistry, OSGiPluginRegistry

public interface PluginRegistry

Loader and registry of Extensions and Extension Points. The implementation of this interface must have a public constructor taking the ClassLoaderResolver interface as argument. The plugin registry metadata/bundle resolution is ruled by OSGi specification. The following sections of the OSGi 3.0 specification must be fully supported: 3.5.2, 3.5.3, 3.2.4, 3.2.5. The section 3.6.3 is optional. All other OSGi parts not mentioned above are not likely to be supported.

See https://dzone.com/articles/extensionserviceplugin-mechanisms-in-java for a comparison of some different plugin mechanisms in Java. The one we use is based around Eclipse extensions/extension points.

Method Summary

Modifier and Type	Method	Description
Object	createExecutableExtension(ConfigurationElement confElm, String name, Class[] argTypes, Object[] args)	Loads a class (do not initialize) from an attribute of ConfigurationElement
Bundle[]	getBundles()	Accessor for all registered bundles
ExtensionPoint	getExtensionPoint(String id)	Acessor for the ExtensionPoint
ExtensionPoint[]	getExtensionPoints()	Acessor for the currently registed ExtensionPoints
Class	loadClass(String pluginId, String className)	Loads a class (do not initialize)
void	registerExtensionPoints()	Look for Bundles/Plugins and register them.
void	registerExtensions()	Look for Bundles/Plugins and register them.
void	resolveConstraints()	Resolve constraints declared in bundle manifest.mf files.
URL	resolveURLAsFileURL(URL url)	Converts a URL that uses a user-defined protocol into a URL that uses the file protocol.

Method Detail

getExtensionPoint

ExtensionPoint getExtensionPoint(String id)

Acessor for the ExtensionPoint

Parameters:

id - the unique id of the extension point

Returns:

null if the ExtensionPoint is not registered

getExtensionPoints

ExtensionPoint[] getExtensionPoints()

Acessor for the currently registed ExtensionPoints

Returns:

array of ExtensionPoints

registerExtensionPoints

void registerExtensionPoints()

Look for Bundles/Plugins and register them. Register also ExtensionPoints and Extensions declared in /plugin.xml files

registerExtensions

void registerExtensions()

Look for Bundles/Plugins and register them. Register also ExtensionPoints and Extensions declared in /plugin.xml files

createExecutableExtension

Object createExecutableExtension(ConfigurationElement confElm,
                                 String name,
                                 Class[] argTypes,
                                 Object[] args)
                          throws ClassNotFoundException,
                                 SecurityException

Loads a class (do not initialize) from an attribute of ConfigurationElement

Parameters:

confElm - the configuration element

name - the attribute name

argTypes - Types of the constructor arguments

args - The arguments

Returns:

the instance

Throws:

ClassNotFoundException - If an error occurs

SecurityException - If an error occurs

loadClass

Class loadClass(String pluginId,
                String className)
         throws ClassNotFoundException

Loads a class (do not initialize)

Parameters:

pluginId - the plugin id

className - the class name

Returns:

the Class

Throws:

ClassNotFoundException - if an error occurs in loading

resolveURLAsFileURL

URL resolveURLAsFileURL(URL url)
                 throws IOException

Converts a URL that uses a user-defined protocol into a URL that uses the file protocol.

Parameters:

url - the url to be converted

Returns:

the converted URL

Throws:

IOException - if an error occurs

resolveConstraints

void resolveConstraints()

Resolve constraints declared in bundle manifest.mf files. This must be invoked after registering all bundles. Should log errors if bundles are not resolvable, or raise runtime exceptions.

getBundles

Bundle[] getBundles()

Accessor for all registered bundles

Returns:

the bundles

Throws:

UnsupportedOperationException - if this operation is not supported by the implementation