    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 * @since 1.9
    047 */
    048public class DefaultBeanIntrospector implements BeanIntrospector {
    049    /** The singleton instance of this class. */
    050    public static final BeanIntrospector INSTANCE = new DefaultBeanIntrospector();
    051
    052    /** Constant for argument types of a method that expects no arguments. */
    053    private static final Class<?>[] EMPTY_CLASS_PARAMETERS = new Class[0];
    054
    055    /** Constant for arguments types of a method that expects a list argument. */
    056    private static final Class<?>[] LIST_CLASS_PARAMETER = new Class[] { java.util.List.class };
    057
    058    /** Log instance */
    059    private final Log log = LogFactory.getLog(getClass());
    060
    061    /**
    062     * Private constructor so that no instances can be created.
    063     */
    064    private DefaultBeanIntrospector() {
    065    }
    066
    067    /**
    068     * This method fixes an issue where IndexedPropertyDescriptor behaves
    069     * differently in different versions of the JDK for 'indexed' properties
    070     * which use java.util.List (rather than an array). It implements a
    071     * workaround for Bug 28358. If you have a Bean with the following
    072     * getters/setters for an indexed property:
    073     *
    074     * <pre>
    075     * public List getFoo()
    076     * public Object getFoo(int index)
    077     * public void setFoo(List foo)
    078     * public void setFoo(int index, Object foo)
    079     * </pre>
    080     *
    081     * then the IndexedPropertyDescriptor's getReadMethod() and getWriteMethod()
    082     * behave as follows:
    083     * <ul>
    084     * <li>JDK 1.3.1_04: returns valid Method objects from these methods.</li>
    085     * <li>JDK 1.4.2_05: returns null from these methods.</li>
    086     * </ul>
    087     *
    088     * @param beanClass the current class to be inspected
    089     * @param descriptors the array with property descriptors
    090     */
    091    private void handleIndexedPropertyDescriptors(final Class<?> beanClass,
    092            final PropertyDescriptor[] descriptors) {
    093        for (final PropertyDescriptor pd : descriptors) {
    094            if (pd instanceof IndexedPropertyDescriptor) {
    095                final IndexedPropertyDescriptor descriptor = (IndexedPropertyDescriptor) pd;
    096                final String propName = descriptor.getName().substring(0, 1)
    097                        .toUpperCase()
    098                        + descriptor.getName().substring(1);
    099
    100                if (descriptor.getReadMethod() == null) {
    101                    final String methodName = descriptor.getIndexedReadMethod() != null ? descriptor
    102                            .getIndexedReadMethod().getName() : "get"
    103                            + propName;
    104                    final Method readMethod = MethodUtils
    105                            .getMatchingAccessibleMethod(beanClass, methodName,
    106                                    EMPTY_CLASS_PARAMETERS);
    107                    if (readMethod != null) {
    108                        try {
    109                            descriptor.setReadMethod(readMethod);
    110                        } catch (final Exception e) {
    111                            log.error(
    112                                    "Error setting indexed property read method",
    113                                    e);
    114                        }
    115                    }
    116                }
    117                if (descriptor.getWriteMethod() == null) {
    118                    final String methodName = descriptor.getIndexedWriteMethod() != null ? descriptor
    119                            .getIndexedWriteMethod().getName() : "set"
    120                            + propName;
    121                    Method writeMethod = MethodUtils
    122                            .getMatchingAccessibleMethod(beanClass, methodName,
    123                                    LIST_CLASS_PARAMETER);
    124                    if (writeMethod == null) {
    125                        for (final Method m : beanClass.getMethods()) {
    126                            if (m.getName().equals(methodName)) {
    127                                final Class<?>[] parameterTypes = m.getParameterTypes();
    128                                if (parameterTypes.length == 1
    129                                        && List.class
    130                                                .isAssignableFrom(parameterTypes[0])) {
    131                                    writeMethod = m;
    132                                    break;
    133                                }
    134                            }
    135                        }
    136                    }
    137                    if (writeMethod != null) {
    138                        try {
    139                            descriptor.setWriteMethod(writeMethod);
    140                        } catch (final Exception e) {
    141                            log.error(
    142                                    "Error setting indexed property write method",
    143                                    e);
    144                        }
    145                    }
    146                }
    147            }
    148        }
    149    }
    150
    151    /**
    152     * Performs introspection of a specific Java class. This implementation uses
    153     * the {@code java.beans.Introspector.getBeanInfo()} method to obtain
    154     * all property descriptors for the current class and adds them to the
    155     * passed in introspection context.
    156     *
    157     * @param icontext the introspection context
    158     */
    159    @Override
    160    public void introspect(final IntrospectionContext icontext) {
    161        BeanInfo beanInfo = null;
    162        try {
    163            beanInfo = Introspector.getBeanInfo(icontext.getTargetClass());
    164        } catch (final IntrospectionException e) {
    165            // no descriptors are added to the context
    166            log.error(
    167                    "Error when inspecting class " + icontext.getTargetClass(),
    168                    e);
    169            return;
    170        }
    171
    172        PropertyDescriptor[] descriptors = beanInfo.getPropertyDescriptors();
    173        if (descriptors == null) {
    174            descriptors = new PropertyDescriptor[0];
    175        }
    176
    177        handleIndexedPropertyDescriptors(icontext.getTargetClass(),
    178                descriptors);
    179        icontext.addPropertyDescriptors(descriptors);
    180    }
    181}