org.leialearns.bridge

Class BridgeFactory

java.lang.Object

org.leialearns.bridge.BridgeFactory

public class BridgeFactory
extends Object

Provides a factory with supporting classes that generates implementations of a logical interface whose methods are delegated to various helper objects on both sides of an abstraction separation. See org.leialearns.bridge.

This class is designed for use in Spring to define several beans, one for each logical interface (near type). A bridge factory bean is defined by its far type, i.e., the type of its concrete delegation index. The logical interface is determined by reflection (by looking up the return type of the declareNearType method.

Additional helpers can be specified as desired. Bindings for the methods specified in the logical interface are looked up when the factory is instantiated in the order in which the helpers are given. If a method is not found in one of the helpers it is looked up in the far type. If it is desired to search the far type before some of the helpers, include a null pointer in the array of helpers.

There are five types of helpers:

1. Helper object that uses near types exclusively
2. Class object
3. Helper object that uses far types exclusively
4. Helper object that mixes near and far types
5. null

For helpers of type 2 a new instance is created using the default no-arg constructor for each bridge object that is created by the factory. These instances are not configured by the spring bean factory. The helper null represents the far object. For the other three types of helpers, either the near object or the far object is prepended to the parameter list, as appropriate. The use of helpers of type 4 is strongly discouraged.

In the context of an ORM framework it is common to use not only the DAO of that corresponds the far type as a helper, but also DAOs of other entities. For example, the SymbolDAO can provide a method that finds all symbols that belong to a particular alphabet. This method can be exposed very naturally on the Alphabet bridged object.

Spring configuration example

    <bean id="alphabetFactory" class="org.leialearns.bridge.BridgeFactory">
      <constructor-arg value="org.leialearns.jpa.interaction.AlphabetDTO"/>
      <constructor-arg>
        <array>
          <ref bean="alphabetDAO"/>
          <ref bean="symbolDAO"/>
          <null/> <!-- AlphabetDTO -->
          <value type="java.lang.Class">org.leialearns.logic.interaction.AlphabetAugmenter</value>
        </array>
      </constructor-arg>
    </bean>
 

See Also:

org.leialearns.bridge

Constructor Summary

Constructors

Constructor and Description
BridgeFactory(Class<? extends FarObject<?>> farType, Object... helpers) Creates a new BridgeFactory instance.
BridgeFactory(String farTypeName, Object... helpers) Creates a new BridgeFactory instance.

Method Summary

Methods

Modifier and Type	Method and Description
Class<?>	getFarType() Returns the far type of the bridge.
<T> T	getHelper(Class<T> type) Returns a helper of the given type.
Object[]	getHelpers() Returns the array of helpers used by this factory instance
Object	getNearObject(Object farObject) Finds or creates a near object for the given far object.
Class<?>	getNearType() Returns the near type of the bridge.
void	setRegistry(BridgeHeadTypeRegistry registry) Sets the BridgeHeadTypeRegistry, registers this factory instance with it, and looks up bindings for the methods in the near type.

Methods inherited from class java.lang.Object

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

Constructor Detail

BridgeFactory

public BridgeFactory(String farTypeName,
             Object... helpers)

Creates a new BridgeFactory instance.

Parameters:

farTypeName - The name of the far type class

helpers - The helpers that implement additional methods on the near type

BridgeFactory

public BridgeFactory(Class<? extends FarObject<?>> farType,
             Object... helpers)

Creates a new BridgeFactory instance.

Parameters:

farType - The far type class

helpers - The helpers that implement additional methods on the near type

Method Detail

getNearType

public Class<?> getNearType()

Returns the near type of the bridge.

Returns:

The near type

getFarType

public Class<?> getFarType()

Returns the far type of the bridge.

Returns:

The far type

setRegistry

@Autowired
public void setRegistry(BridgeHeadTypeRegistry registry)

Sets the BridgeHeadTypeRegistry, registers this factory instance with it, and looks up bindings for the methods in the near type.

Parameters:

registry - The BridgeHeadTypeRegistry instance to use

getNearObject

public Object getNearObject(Object farObject)

Finds or creates a near object for the given far object.

Parameters:

farObject - The far object that is to be wrapped by the near object

Returns:

The near object that corresponds to the given far object

getHelpers

public Object[] getHelpers()

Returns the array of helpers used by this factory instance

Returns:

The array of helpers used by this factory instance

getHelper

public <T> T getHelper(Class<T> type)

Returns a helper of the given type. If more than one helper is an instance of the type, then the one that occurs first in the helper array is returned. An IllegalStateException is thrown when no helper is found.

Parameters:

type - The type of the requested helper

Returns:

The requested helper