1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.beanutils2.converters;
18
19 /**
20 * {@link org.apache.commons.beanutils2.Converter} implementation that handles conversion to and from <strong>java.lang.Class</strong> objects.
21 * <p>
22 * The class will be loaded from the thread context class loader (if it exists); otherwise the class loader that loaded this class will be used.
23 * <p>
24 * Can be configured to either return a <em>default value</em> or throw a {@code ConversionException} if a conversion error occurs.
25 *
26 * @param <T> the type of the class.
27 * @since 1.4
28 */
29 public final class ClassConverter<T> extends AbstractConverter<Class<T>> {
30
31 /**
32 * Constructs a <strong>java.lang.Class</strong> <em>Converter</em> that throws a {@code ConversionException} if an error occurs.
33 */
34 public ClassConverter() {
35 }
36
37 /**
38 * Constructs a <strong>java.lang.Class</strong> <em>Converter</em> that returns a default value if an error occurs.
39 *
40 * @param defaultValue The default value to be returned if the value to be converted is missing or an error occurs converting the value.
41 */
42 public ClassConverter(final Class<T> defaultValue) {
43 super(defaultValue);
44 }
45
46 /**
47 * <p>
48 * Converts a java.lang.Class or object into a String.
49 * </p>
50 *
51 * @param value The input value to be converted
52 * @return the converted String value.
53 * @since 1.8.0
54 */
55 @Override
56 protected String convertToString(final Object value) {
57 return value instanceof Class ? ((Class<?>) value).getName() : value.toString();
58 }
59
60 /**
61 * <p>
62 * Converts the input object into a java.lang.Class.
63 * </p>
64 *
65 * @param <R> Target type of the conversion.
66 * @param type Data type to which this value should be converted.
67 * @param value The input value to be converted.
68 * @return The converted value.
69 * @throws Throwable if an error occurs converting to the specified type
70 * @since 1.8.0
71 */
72 @Override
73 protected <R> R convertToType(final Class<R> type, final Object value) throws Throwable {
74 if (Class.class.equals(type)) {
75 ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
76 if (classLoader != null) {
77 try {
78 return type.cast(classLoader.loadClass(value.toString()));
79 } catch (final ClassNotFoundException ex) {
80 // Don't fail, carry on and try this class's class loader
81 // (see issue# BEANUTILS-263)
82 }
83 }
84
85 // Try this class's class loader
86 classLoader = ClassConverter.class.getClassLoader();
87 return type.cast(classLoader.loadClass(value.toString()));
88 }
89
90 throw conversionException(type, value);
91 }
92
93 /**
94 * Gets the default type this {@code Converter} handles.
95 *
96 * @return The default type this {@code Converter} handles.
97 * @since 1.8.0
98 */
99 @SuppressWarnings({ "unchecked", "rawtypes" })
100 @Override
101 protected Class<Class<T>> getDefaultType() {
102 return (Class) Class.class;
103 }
104
105 }