mirror of https://github.com/octoleo/plantuml.git
121 lines
4.8 KiB
Java
121 lines
4.8 KiB
Java
/*
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* Copyright 2003-2004, Franz-Josef Elmer, All rights reserved
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details
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* (http://www.gnu.org/copyleft/lesser.html).
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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package jcckit.util;
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import java.lang.reflect.Constructor;
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/**
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* General purpose factory method based on {@link ConfigParameters}
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* and Java's Reflection API.
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*
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* @author Franz-Josef Elmer
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*/
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public class Factory {
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/** The constant defining the key <tt>className</tt>. */
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public static final String CLASS_NAME_KEY = "className";
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/** No public constructor necessary. */
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private Factory() {}
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/**
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* Creates an instance of the specified class.
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* @param className Fully-qualified name of a class with a default
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* constructor.
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* @return a new instance.
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* @throws IllegalArgumentException if the instance could be created.
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*/
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public static Object create(String className) {
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try {
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return Class.forName(className).newInstance();
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} catch (Throwable t) {
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throw new IllegalArgumentException("Could not create an instance of "
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+ className + " because of " + t);
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}
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}
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/**
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* Creates an object based on the specified configuration
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* parameters. The class of the object is determined by the
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* parameter with the key {@link #CLASS_NAME_KEY}.
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* The constructor with a single argument of the type
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* <tt>ConfigParameter</tt> is invoked with the argument
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* <tt>configParameters</tt>. If such a constructor
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* does not exists the default constructor is invoked. If
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* neither of these constructors exist a {@link FactoryException}
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* is thrown.
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* @param configParameters Configuration parameters.
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* @return the newly created object.
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* @throws IllegalArgumentException if key <tt>className</tt> is missing.
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* @throws FactoryException wrapping any kind of exception or error occured.
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*/
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public static Object create(ConfigParameters configParameters) {
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String className = configParameters.get(CLASS_NAME_KEY);
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return createObject(configParameters, className);
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}
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/**
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* Creates an object based on the specified configuration
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* parameters and default class name. If the
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* parameter with the key {@link #CLASS_NAME_KEY} is missed in
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* <tt>configParameters</tt> <tt>defaultClassName</tt> is used.
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* Otherwise it works as {@link #create(jcckit.util.ConfigParameters)}.
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* @param configParameters Configuration parameters.
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* @param defaultClassName Default class name.
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* @return the newly created object.
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* @throws FactoryException wrapping any kind of exception or error occured.
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*/
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public static Object create(ConfigParameters configParameters,
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String defaultClassName) {
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String className = configParameters.get(CLASS_NAME_KEY, defaultClassName);
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return createObject(configParameters, className);
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}
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/**
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* Creates an object based on the specified configuration
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* parameters or returns the default object. This method behaves
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* as {@link #create(jcckit.util.ConfigParameters)}, except that is does
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* not throw an <tt>IllegalArgumentException</tt> if key <tt>className</tt>
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* is missing. Instead <tt>defaultObject</tt> is returned.
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*/
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public static Object createOrGet(ConfigParameters configParameters,
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Object defaultObject) {
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String className = configParameters.get(CLASS_NAME_KEY, null);
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return className == null ? defaultObject
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: createObject(configParameters, className);
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}
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private static Object createObject(ConfigParameters configParameters,
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String className) {
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try {
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Class c = Class.forName(className);
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Object result = null;
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Constructor constructor = null;
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try {
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constructor = c.getConstructor(new Class[] {ConfigParameters.class});
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result = constructor.newInstance(new Object[] {configParameters});
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} catch (NoSuchMethodException e) {
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result = c.newInstance();
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}
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return result;
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} catch (Throwable t) {
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throw new FactoryException(configParameters, CLASS_NAME_KEY, t);
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}
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}
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}
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