org.mule.extension

Interface ExtensionManager

public interface ExtensionManager

Manages the Extensions available in the current context and their state. Going beyond the introspection model defined by Extension, Configuration and Operation class, at runtime there will be instances implementing the extension components modeled by them. Those instances need to be registered with this manager in order to be used.

The workflow for this manager would be to first discover the currently available extensions through discoverExtensions(ClassLoader). Additionally, Extension instances can also be added in runtime through registerExtension(Extension).

Instances serving as realization of a Configuration model need to be registered with the registerConfigurationInstanceProvider(String, ConfigurationInstanceProvider) method in orderfor this manager to provision the underlying infrastructure to host and execute such configuration. Oncea configuration is registered, then operations can be executed with it by requesting a OperationExecutor to the getOperationExecutor(String, OperationContext) or getOperationExecutor(OperationContext) methods

Since:

1.0

Method Summary

Methods

Modifier and Type	Method and Description
List<Extension>	discoverExtensions(ClassLoader classLoader) Scans the classpath visible to the given ClassLoader and registers them.
Set<Extension>	getExtensions() Returns a Set listing all the available Extensions.
<C> Set<Extension>	getExtensionsCapableOf(Class<C> capability) Returns a Set with the Extensions that have the given capability
OperationExecutor	getOperationExecutor(OperationContext operationContext) Provisions a OperationExecutor to execute the Operation that is referenced by operationContext.
OperationExecutor	getOperationExecutor(String configurationInstanceProviderName, OperationContext operationContext) Provisions a OperationExecutor to execute the Operation that is referenced by operationContext.
<C> void	registerConfigurationInstanceProvider(String providerName, ConfigurationInstanceProvider<C> configurationInstanceProvider) Registers the configurationInstanceProvider.
boolean	registerExtension(Extension extension) Registers the given Extension If a matching Extension is already registered, then this manager will apply whatever policy finds more convenient to decide if the existing registration is kept or replaced.

Method Detail

discoverExtensions

List<Extension> discoverExtensions(ClassLoader classLoader)

Scans the classpath visible to the given ClassLoader and registers them.

The discovery process works as follows:

• Standard Java SPI mechanism is used to discover implementations of the Describer interface
• The discovered describers are fed into a ExtensionFactory and transformed in Extension instances
• Those extensions are registered through the registerExtension(Extension) method

Finally, a List will be returned with the Extensions that were registered or modified. For instance, the first time this method is invoked, all the discovered extensions will be returned. If it's then called again, the extensions that are already registered will not be present in the newly returned list, only those that were not there the first time or that were modified. If no extensions are found, or nothing has changed since the last discovery, then an empty list is returned

Parameters:

classLoader - a not null ClassLoader in which to search for extensions

Returns:

a List with the registered or updated Extensions or an empty list if none is found or updated

registerExtension

boolean registerExtension(Extension extension)

Registers the given Extension If a matching Extension is already registered, then this manager will apply whatever policy finds more convenient to decide if the existing registration is kept or replaced. That is up to the implementation. The only thing this contract guarantees is that each extension type will be registered only once and that the discovery process will not fail if many discovery runs are triggered over the same classpath.

Parameters:

extension - the Extension to be registered. Cannot be null

Returns:

true if the extension was registered. false if the platform decided to kept an existing declaration

getExtensions

Set<Extension> getExtensions()

Returns a Set listing all the available Extensions.

Returns:

an Set. Will not be null but might be empty

getExtensionsCapableOf

<C> Set<Extension> getExtensionsCapableOf(Class<C> capability)

Returns a Set with the Extensions that have the given capability

Parameters:

capability - a Class representing a capability

Returns:

a Set with the matching Extensions. It might be null but will never be empty

registerConfigurationInstanceProvider

<C> void registerConfigurationInstanceProvider(String providerName,
                                             ConfigurationInstanceProvider<C> configurationInstanceProvider)

Registers the configurationInstanceProvider. The provider can later be referenced by the given providerName

Type Parameters:

C - the type of the configurations instances that configurationInstanceProvider provides

Parameters:

providerName - the name under which the configurationInstanceProvider will be referenced

configurationInstanceProvider - a ConfigurationInstanceProvider

getOperationExecutor

OperationExecutor getOperationExecutor(String configurationInstanceProviderName,
                                     OperationContext operationContext)

Provisions a OperationExecutor to execute the Operation that is referenced by operationContext. This method also requires referencing the ConfigurationInstanceProvider that will be used to obtain a configuration instance. That reference is done through the configurationInstanceProviderName parameter which must point to a ConfigurationInstanceProvider previously registered through registerConfigurationInstanceProvider(String, ConfigurationInstanceProvider)

Parameters:

configurationInstanceProviderName - the name of the ConfigurationInstanceProvider used to obtain a configuration instance

operationContext - a OperationContext

Returns:

a functional OperationExecutor

getOperationExecutor

OperationExecutor getOperationExecutor(OperationContext operationContext)

Provisions a OperationExecutor to execute the Operation that is referenced by operationContext.

Because this method makes no reference to a particular ConfigurationInstanceProvider, the platform will choose one by following criteria:

• If only one ConfigurationInstanceProvider was registered through registerConfigurationInstanceProvider(String, ConfigurationInstanceProvider) for the Extension that owns the Operation, then that provider will be used
• If more than one were registered, then an IllegalStateException will be thrown
• If no ConfigurationInstanceProvider was registered, then the platform will evaluate all the Configurations on the Extension looking for those which can be created implicitly. If any are found, then the first one is selected and a ConfigurationInstanceProvider will be created and registered for it.

It is considered that a Configuration can be created implicitly if for all its Parameters it can be said that they're optional or/and have a default value. In such case, the platform will create an instance which respects those defaults and has null values for the rest of the parameters.

Parameters:

operationContext - a OperationContext

Returns:

a functional OperationExecutor