uk.ac.starlink.util

Class ObjectFactory<T>

java.lang.Object

uk.ac.starlink.util.ObjectFactory<T>

public class ObjectFactory<T>
extends Object

Manages dynamic creation of objects from a known set of classes. An ObjectFactory keeps a list of classes with associated nicknames; the idea is that you can obtain an instance of a given class by supplying the nickname in question. Instead of a nickname you can use the fully qualified classname, whether or not it has previously been registered. Any class registered must be a subclass of the superclass specified when this factory is constructed, and must have a no-arg constructor.

Since:

10 Aug 2005

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
ObjectFactory(Class<T> clazz) Constructor.

Method Summary

Modifier and Type	Method and Description
T	createObject(String spec) Constructs and returns an object from one of the classes registered with this factory.
Class<T>	getFactoryClass() Returns the class of which any object created by this factory is guaranteed to be an instance.
String	getNickName(Class<? extends T> clazz) Returns the nickname corresponding to the no-arg constructor of the given class.
String[]	getNickNames() Returns a list of the nicknames which have been registered.
boolean	isRegistered(String name) Indicates whether this factory knows about a given name.
void	register(String nickName, String className) Registers a class with its nickname.

Methods inherited from class java.lang.Object

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

Constructor Detail

ObjectFactory

public ObjectFactory(Class<T> clazz)

Constructor.

Parameters:

clazz - type which must be a supertype of any class registered with this factory

Method Detail

getFactoryClass

public Class<T> getFactoryClass()

Returns the class of which any object created by this factory is guaranteed to be an instance.

Returns:

clazz

register

public void register(String nickName,
                     String className)

Registers a class with its nickname.

Parameters:

nickName - nickname

className - fully-qualified class name

getNickNames

public String[] getNickNames()

Returns a list of the nicknames which have been registered.

Returns:

nickname array

isRegistered

public boolean isRegistered(String name)

Indicates whether this factory knows about a given name. This may either be a registered nickname or a fully qualified classname for a class which is a subclass of this factory's produced class.

Parameters:

name - name

Returns:

true iff name can sensibly be passed to createObject(java.lang.String)

createObject

public T createObject(String spec)
               throws LoadException

Constructs and returns an object from one of the classes registered with this factory. If construction fails because the required class is not on the classpath or there is some error in class initialization, a LoadException is thrown. If the class is of the wrong sort (has no no-arg constructor, is not a subtype of this factory's supertype) a RuntimeException will be thrown.

Parameters:

spec - classname/nickname of class to instantiate, followed by optional config text

Throws:

LoadException - if the load fails for unsurprising reasons

See Also:

BeanConfig

getNickName

public String getNickName(Class<? extends T> clazz)

Returns the nickname corresponding to the no-arg constructor of the given class.

Parameters:

clazz - class to be constructed by this factory

Returns:

nickname associated with no-arg constructor of supplied class, or null