io.cdap.wrangler.registry

Class UserDirectiveRegistry

java.lang.Object

io.cdap.wrangler.registry.UserDirectiveRegistry

All Implemented Interfaces:

DirectiveRegistry, Closeable, AutoCloseable

public final class UserDirectiveRegistry
extends Object
implements DirectiveRegistry

A User Executor Registry in a collection of user defined directives. The class UserDirectiveRegistry loads the directive either as an ArtifactInfo or through the use of the context in which it is running. This class provides two constructors for two different context in which the user defined directives are loaded.

One context is the service context in which construction of this object would result in investigating all the different artifacts that are of type Directive.TYPE and creating a classloader for the same. The classload is then used to create an instance of plugin, in this case it's a directive and extract all the DirectiveInfo from the instance of directive created.

Second context is the Transform plugin, were the second constructor of this class in used to initialize. Initializing this class using StageContext provides a way to create an instance of the plugin. The name of the directive is used as the id for the plugin.

See Also:

SystemDirectiveRegistry, CompositeDirectiveRegistry

Constructor Summary

Constructors

Constructor and Description
UserDirectiveRegistry(HttpServiceContext manager) This constructor should be used when initializing the registry from Service.
UserDirectiveRegistry(StageContext context) This constructor is used when constructing this object in the context of Transform.
UserDirectiveRegistry(SystemAppTaskContext systemAppTaskContext) This constructor is used when creating from remote task

Method Summary

Modifier and Type	Method and Description
void	close() Closes any resources acquired during initialization or otherwise.
DirectiveInfo	get(String namespace, String name) This method provides information about the directive that is being requested.
ArtifactSummary	getLatestWranglerArtifact() Retrieve latest Wrangler transform artifact information
Iterable<DirectiveInfo>	list(String namespace) List the directives in the specified namespace
void	reload(String namespace) This method reloads the directives from the artifacts into the registry.

Methods inherited from class java.lang.Object

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

Constructor Detail

UserDirectiveRegistry

public UserDirectiveRegistry(HttpServiceContext manager)

This constructor should be used when initializing the registry from Service.

Service context implements ArtifactManager interface so it should be readily assignable.

Using the ArtifactManager, all the artifacts are inspected to check for the artifacts that contain plugins of type Directive#Type. For all those plugins, an instance of the plugin is created to extract the annotated and basic information.

Parameters:

manager - an instance of ArtifactManager.

UserDirectiveRegistry

public UserDirectiveRegistry(SystemAppTaskContext systemAppTaskContext)

This constructor is used when creating from remote task

Parameters:

systemAppTaskContext - SystemAppTaskContext

UserDirectiveRegistry

public UserDirectiveRegistry(StageContext context)

This constructor is used when constructing this object in the context of Transform. A instance of StageContext is passed to load plugin. Context allows loading the plugin from the repository. The directive name is used as the plugin id for loading the class.

Parameters:

context - of Stage in Transform.

Method Detail

get

public DirectiveInfo get(String namespace,
                         String name)
                  throws DirectiveLoadException

This method provides information about the directive that is being requested.

First, the directive is checked for existence with the internal registry. If the directive does not exits in the registry and the context is not null, then it's attempted to be loaded as a user plugin. If it does not exist there a null is returned. But, if the plugin exists, then it's loaded and an entry is made into the registry.

When invoked through a readable, each plugin is assigned a unique id. The unique id is generated during the configure phase of the plugin. Those ids are passed to initialize through the properties.

Specified by:

get in interface DirectiveRegistry

Parameters:

name - of the directive to be retrived from the registry.

namespace - the namespace of the directive

Returns:

an instance of DirectiveInfo if found, else null.

Throws:

DirectiveLoadException

reload

public void reload(String namespace)
            throws DirectiveLoadException

Description copied from interface: DirectiveRegistry

This method reloads the directives from the artifacts into the registry. Any implementation of this method should provide support for deletes, updates and additions.

Specified by:

reload in interface DirectiveRegistry

Parameters:

namespace - the namespace to reload directives in

Throws:

DirectiveLoadException - thrown when there are any issues with loading directives into the registry.

getLatestWranglerArtifact

@Nullable
public ArtifactSummary getLatestWranglerArtifact()

Description copied from interface: DirectiveRegistry

Retrieve latest Wrangler transform artifact information

Specified by:

getLatestWranglerArtifact in interface DirectiveRegistry

list

public Iterable<DirectiveInfo> list(String namespace)

Description copied from interface: DirectiveRegistry

List the directives in the specified namespace

Specified by:

list in interface DirectiveRegistry

Parameters:

namespace - the namespace to list from

Returns:

Returns an iterator to iterate through all the DirectiveInfo objects maintained within the registry.

close

public void close()
           throws IOException

Closes any resources acquired during initialization or otherwise.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException