Package org.apache.sis.internal.system

Class OptionalDependency

java.lang.Object

org.apache.sis.internal.system.SystemListener

org.apache.sis.internal.system.OptionalDependency

All Implemented Interfaces:

EventListener

Direct Known Subclasses:

MetadataServices, ReferencingServices

public abstract class OptionalDependency
extends SystemListener

Base class of internal hooks for accessing optional dependencies. This is used for example for allowing the "sis-metadata" module to access some services of the "sis-referencing" module if the latter is present on the classpath.

Since:

0.6

Version:

0.6

Field Summary

Fields

Modifier and Type	Field	Description
private final String	dependency	The name of the optional module on which we depend.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	OptionalDependency(String module, String dependency)	Creates a new optional dependency.

Method Summary

Modifier and Type	Method	Description
protected void	classpathChanged()	Invoked when the classpath is likely to have changed.
protected static <T extends OptionalDependency> T	getInstance(Class<T> type, String module, String dependency, String implementation)	Returns the optional dependency, or null if not found.
protected final UnsupportedOperationException	moduleNotFound()	Returns the exception to throw when a method requiring the optional dependency is invoked but that module is not on the classpath.

Methods inherited from class org.apache.sis.internal.system.SystemListener

add, databaseChanged, fireClasspathChanged, remove, removeModule

Methods inherited from class java.lang.Object

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

Field Details

dependency

private final String dependency

The name of the optional module on which we depend.

Constructor Details

OptionalDependency

protected OptionalDependency(String module,
 String dependency)

Creates a new optional dependency.

Parameters:

module - a constant from the Modules class which identify the module that need the optional dependency.

dependency - the Maven artifact name (not a name from the Modules class) of the optional module on which the module depend.

Method Details

classpathChanged

protected void classpathChanged()

Invoked when the classpath is likely to have changed. Subclasses must override like below:

Specified by:

classpathChanged in class SystemListener

getInstance

protected static <T extends OptionalDependency> T getInstance(Class<T> type,
 String module,
 String dependency,
 String implementation)

Returns the optional dependency, or null if not found. This is a helper method for implementation of getInstance() static method in subclasses.

Type Parameters:

T - compile-time type of the type argument.

Parameters:

type - the subclass type.

module - same argument value than the one given to the constructor.

dependency - same argument value than the one given to the constructor.

implementation - the fully-qualified name of the class to instantiate by reflection.

Returns:

an instance of the implementation class, or null if not found.

moduleNotFound

protected final UnsupportedOperationException moduleNotFound()

Returns the exception to throw when a method requiring the optional dependency is invoked but that module is not on the classpath.

Returns:

the exception to throw.