| /******************************************************************************* |
| * Copyright (c) 2005, 2011 Oracle. All rights reserved. |
| * This program and the accompanying materials are made available under the |
| * terms of the Eclipse Public License v1.0, which accompanies this distribution |
| * and is available at http://www.eclipse.org/legal/epl-v10.html. |
| * |
| * Contributors: |
| * Oracle - initial API and implementation |
| ******************************************************************************/ |
| package org.eclipse.jpt.common.utility.internal; |
| |
| import java.io.Serializable; |
| |
| /** |
| * Used by various "pluggable" classes to transform objects. |
| * Transform an object of type <code>T1</code> to an object of type |
| * <code>T2</code>. |
| * |
| * @param <T1> the type of the object passed to the transformer |
| * @param <T2> the type of the object returned by the transformer |
| */ |
| public interface Transformer<T1, T2> { |
| |
| /** |
| * Return the transformed object. |
| * The semantics of "transform" is determined by the |
| * contract between the client and the server. |
| */ |
| T2 transform(T1 o); |
| |
| |
| /** |
| * A "null" transformer will perform no transformation at all; |
| * it will simply return the object "untransformed". |
| */ |
| final class Null<S1, S2> |
| implements Transformer<S1, S2>, Serializable |
| { |
| @SuppressWarnings("rawtypes") |
| public static final Transformer INSTANCE = new Null(); |
| @SuppressWarnings("unchecked") |
| public static <R1, R2> Transformer<R1, R2> instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Null() { |
| super(); |
| } |
| // simply return the object, unchanged |
| @SuppressWarnings("unchecked") |
| public S2 transform(S1 o) { |
| return (S2) o; |
| } |
| @Override |
| public String toString() { |
| return StringTools.buildSingletonToString(this); |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| |
| /** |
| * A "disabled" transformer will throw an exception if |
| * {@link #transform(Object)} is called. This is useful in situations |
| * where a transformer is optional and the default transformer should |
| * not be used. |
| */ |
| final class Disabled<S1, S2> |
| implements Transformer<S1, S2>, Serializable |
| { |
| @SuppressWarnings("rawtypes") |
| public static final Transformer INSTANCE = new Disabled(); |
| @SuppressWarnings("unchecked") |
| public static <R1, R2> Transformer<R1, R2> instance() { |
| return INSTANCE; |
| } |
| // ensure single instance |
| private Disabled() { |
| super(); |
| } |
| // throw an exception |
| public S2 transform(S1 o) { |
| throw new UnsupportedOperationException(); |
| } |
| @Override |
| public String toString() { |
| return StringTools.buildSingletonToString(this); |
| } |
| private static final long serialVersionUID = 1L; |
| private Object readResolve() { |
| // replace this object with the singleton |
| return INSTANCE; |
| } |
| } |
| } |