    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.beanutils;
    018
    019import java.beans.BeanInfo;
    020import java.beans.IndexedPropertyDescriptor;
    021import java.beans.IntrospectionException;
    022import java.beans.Introspector;
    023import java.beans.PropertyDescriptor;
    024import java.lang.reflect.Method;
    025import java.util.List;
    026
    027import org.apache.commons.logging.Log;
    028import org.apache.commons.logging.LogFactory;
    029
    030/**
    031 * <p>
    032 * The default {@link BeanIntrospector} implementation.
    033 * </p>
    034 * <p>
    035 * This class implements a default bean introspection algorithm based on the JDK
    036 * classes in the <code>java.beans</code> package. It discovers properties
    037 * conforming to the Java Beans specification.
    038 * </p>
    039 * <p>
    040 * This class is a singleton. The single instance can be obtained using the
    041 * {@code INSTANCE} field. It does not define any state and thus can be
    042 * shared by arbitrary clients. {@link PropertyUtils} per default uses this
    043 * instance as its only {@code BeanIntrospector} object.
    044 * </p>
    045 *
    046 * @version $Id$
    047 * @since 1.9
    048 */
    049public class DefaultBeanIntrospector implements BeanIntrospector {
    050    /** The singleton instance of this class. */
    051    public static final BeanIntrospector INSTANCE = new DefaultBeanIntrospector();
    052
    053    /** Constant for argument types of a method that expects no arguments. */
    054    private static final Class<?>[] EMPTY_CLASS_PARAMETERS = new Class[0];
    055
    056    /** Constant for arguments types of a method that expects a list argument. */
    057    private static final Class<?>[] LIST_CLASS_PARAMETER = new Class[] { java.util.List.class };
    058
    059    /** Log instance */
    060    private final Log log = LogFactory.getLog(getClass());
    061
    062    /**
    063     * Private constructor so that no instances can be created.
    064     */
    065    private DefaultBeanIntrospector() {
    066    }
    067
    068    /**
    069     * Performs introspection of a specific Java class. This implementation uses
    070     * the {@code java.beans.Introspector.getBeanInfo()} method to obtain
    071     * all property descriptors for the current class and adds them to the
    072     * passed in introspection context.
    073     *
    074     * @param icontext the introspection context
    075     */
    076    public void introspect(final IntrospectionContext icontext) {
    077        BeanInfo beanInfo = null;
    078        try {
    079            beanInfo = Introspector.getBeanInfo(icontext.getTargetClass());
    080        } catch (final IntrospectionException e) {
    081            // no descriptors are added to the context
    082            log.error(
    083                    "Error when inspecting class " + icontext.getTargetClass(),
    084                    e);
    085            return;
    086        }
    087
    088        PropertyDescriptor[] descriptors = beanInfo.getPropertyDescriptors();
    089        if (descriptors == null) {
    090            descriptors = new PropertyDescriptor[0];
    091        }
    092
    093        handleIndexedPropertyDescriptors(icontext.getTargetClass(),
    094                descriptors);
    095        icontext.addPropertyDescriptors(descriptors);
    096    }
    097
    098    /**
    099     * This method fixes an issue where IndexedPropertyDescriptor behaves
    100     * differently in different versions of the JDK for 'indexed' properties
    101     * which use java.util.List (rather than an array). It implements a
    102     * workaround for Bug 28358. If you have a Bean with the following
    103     * getters/setters for an indexed property:
    104     *
    105     * <pre>
    106     * public List getFoo()
    107     * public Object getFoo(int index)
    108     * public void setFoo(List foo)
    109     * public void setFoo(int index, Object foo)
    110     * </pre>
    111     *
    112     * then the IndexedPropertyDescriptor's getReadMethod() and getWriteMethod()
    113     * behave as follows:
    114     * <ul>
    115     * <li>JDK 1.3.1_04: returns valid Method objects from these methods.</li>
    116     * <li>JDK 1.4.2_05: returns null from these methods.</li>
    117     * </ul>
    118     *
    119     * @param beanClass the current class to be inspected
    120     * @param descriptors the array with property descriptors
    121     */
    122    private void handleIndexedPropertyDescriptors(final Class<?> beanClass,
    123            final PropertyDescriptor[] descriptors) {
    124        for (final PropertyDescriptor pd : descriptors) {
    125            if (pd instanceof IndexedPropertyDescriptor) {
    126                final IndexedPropertyDescriptor descriptor = (IndexedPropertyDescriptor) pd;
    127                final String propName = descriptor.getName().substring(0, 1)
    128                        .toUpperCase()
    129                        + descriptor.getName().substring(1);
    130
    131                if (descriptor.getReadMethod() == null) {
    132                    final String methodName = descriptor.getIndexedReadMethod() != null ? descriptor
    133                            .getIndexedReadMethod().getName() : "get"
    134                            + propName;
    135                    final Method readMethod = MethodUtils
    136                            .getMatchingAccessibleMethod(beanClass, methodName,
    137                                    EMPTY_CLASS_PARAMETERS);
    138                    if (readMethod != null) {
    139                        try {
    140                            descriptor.setReadMethod(readMethod);
    141                        } catch (final Exception e) {
    142                            log.error(
    143                                    "Error setting indexed property read method",
    144                                    e);
    145                        }
    146                    }
    147                }
    148                if (descriptor.getWriteMethod() == null) {
    149                    final String methodName = descriptor.getIndexedWriteMethod() != null ? descriptor
    150                            .getIndexedWriteMethod().getName() : "set"
    151                            + propName;
    152                    Method writeMethod = MethodUtils
    153                            .getMatchingAccessibleMethod(beanClass, methodName,
    154                                    LIST_CLASS_PARAMETER);
    155                    if (writeMethod == null) {
    156                        for (final Method m : beanClass.getMethods()) {
    157                            if (m.getName().equals(methodName)) {
    158                                final Class<?>[] parameterTypes = m.getParameterTypes();
    159                                if (parameterTypes.length == 1
    160                                        && List.class
    161                                                .isAssignableFrom(parameterTypes[0])) {
    162                                    writeMethod = m;
    163                                    break;
    164                                }
    165                            }
    166                        }
    167                    }
    168                    if (writeMethod != null) {
    169                        try {
    170                            descriptor.setWriteMethod(writeMethod);
    171                        } catch (final Exception e) {
    172                            log.error(
    173                                    "Error setting indexed property write method",
    174                                    e);
    175                        }
    176                    }
    177                }
    178            }
    179        }
    180    }
    181}