ca.infoway.messagebuilder.service
Class ServiceFactory<T>

java.lang.Object
  ca.infoway.messagebuilder.service.ServiceFactory<T>

Type Parameters:

T - - the interface type of the service

Direct Known Subclasses:

MessageDefinitionServiceFactory

public abstract class ServiceFactory<T>
extends Object

A common Java practice for allowing configurable implementations of a service interface is to look for a file in the META-INF directory of a jar. An example of this problem is XML parsing. There's an abstract factory type called javax.xml.parsers.DocumentBuilderFactory, and the expectation is that some component will provide a concrete implementation of this type.

The Java way of handling that is to look for a file in the META-INF directory called /META-INF/javax.xml.parsers.DocumentBuilderFactory

The file is a simple text file that contains the fully-qualified name of an implementing class, and Java can decide to pick one (or many) of those implementations.

This class implements behaviour like that -- it looks for a set of resources on the classpath, named after a specific type, and finds the corresponding classes.

Author:

Intelliware Development

Constructor Summary

ServiceFactory(Class<T> c)
Standard constructor.

Method Summary

protected abstract T	chooseImplementationOfService(List<T> services) Choose an implementation of a service, based on several options.
T	create() Create an instance of the service.
protected abstract T	createTrivialService() Create a trivial service if no other option exists.
protected List<T>	getServices(Enumeration<URL> resources) Find all implementations of the message definition service.

Methods inherited from class java.lang.Object

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

Constructor Detail

ServiceFactory

public ServiceFactory(Class<T> c)

Standard constructor.

Parameters:

c - - the type of service that the factory finds

Method Detail

create

public T create()

Create an instance of the service.

Returns:

- the instance of the service.

chooseImplementationOfService

protected abstract T chooseImplementationOfService(List<T> services)

Choose an implementation of a service, based on several options.

Returns:

- the instance of the service.

createTrivialService

protected abstract T createTrivialService()

Create a trivial service if no other option exists.

Returns:

- the trivial service.

getServices

protected List<T> getServices(Enumeration<URL> resources)
                       throws IOException

Find all implementations of the message definition service.

Parameters:

resources - - an enumeration of all the URLs to service files

Returns:

- a list of instances that implement the service interface.

Throws:

IOException - - if any resource cannot be accessed.