001 /*
002 * Copyright 2003-2004 The Apache Software Foundation
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016 package org.apache.commons.convert1.string;
017
018
019 import org.apache.commons.convert1.ConversionException;
020 import org.apache.commons.convert1.Converter;
021
022
023 /**
024 * <p>Standard {@link Converter} implementation that converts an incoming
025 * String into a <code>java.lang.Class</code> object, optionally using a
026 * default value or throwing a {@link ConversionException} if a conversion
027 * error occurs. The class will be loaded from the thread context class
028 * loader (if it exists); otherwise the class loader that loaded this class
029 * will be used.</p>
030 *
031 * @author Tomas Viberg
032 * @version $Id: ClassConverter.java 155441 2005-02-26 13:19:22Z dirkv $
033 * @since 0.1
034 */
035
036 public final class ClassConverter implements Converter {
037
038
039 // ----------------------------------------------------------- Constructors
040
041
042 /**
043 * Create a {@link Converter} that will throw a {@link ConversionException}
044 * if a conversion error occurs.
045 */
046 public ClassConverter() {
047
048 this.defaultValue = null;
049 this.useDefault = false;
050
051 }
052
053
054 /**
055 * Create a {@link Converter} that will return the specified default value
056 * if a conversion error occurs.
057 *
058 * @param defaultValue The default value to be returned
059 */
060 public ClassConverter(Object defaultValue) {
061
062 this.defaultValue = defaultValue;
063 this.useDefault = true;
064
065 }
066
067
068 // ----------------------------------------------------- Instance Variables
069
070
071 /**
072 * The default value specified to our Constructor, if any.
073 */
074 private Object defaultValue = null;
075
076
077 /**
078 * Should we return the default value on conversion errors?
079 */
080 private boolean useDefault = true;
081
082
083 // --------------------------------------------------------- Public Methods
084
085
086 /**
087 * Convert the specified input object into an output object of the
088 * specified type.
089 *
090 * @param type Data type to which this value should be converted
091 * @param value The input value to be converted
092 *
093 * @exception ConversionException if conversion cannot be performed
094 * successfully
095 */
096 public Object convert(Class type, Object value) {
097
098 if (value == null) {
099 if (useDefault) {
100 return (defaultValue);
101 } else {
102 throw new ConversionException("No value specified");
103 }
104 }
105
106 if (value instanceof Class) {
107 return (value);
108 }
109
110 try {
111 ClassLoader classLoader =
112 Thread.currentThread().getContextClassLoader();
113 if (classLoader == null) {
114 classLoader = ClassConverter.class.getClassLoader();
115 }
116 return (classLoader.loadClass(value.toString()));
117 } catch (Exception e) {
118 if (useDefault) {
119 return (defaultValue);
120 } else {
121 throw new ConversionException(e);
122 }
123 }
124
125 }
126
127
128 }