    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.beanutils2;
    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 classes in the {@link java.beans} package. It discovers properties conforming
    036 * to the Java Beans specification.
    037 * </p>
    038 * <p>
    039 * This class is a singleton. The single instance can be obtained using the {@code INSTANCE} field. It does not define any state and thus can be shared by
    040 * arbitrary clients. {@link PropertyUtils} per default uses this instance as its only {@code BeanIntrospector} object.
    041 * </p>
    042 *
    043 * @since 1.9
    044 */
    045public class DefaultBeanIntrospector implements BeanIntrospector {
    046
    047    /** The singleton instance of this class. */
    048    public static final BeanIntrospector INSTANCE = new DefaultBeanIntrospector();
    049
    050    /** Constant for arguments types of a method that expects a list argument. */
    051    private static final Class<?>[] LIST_CLASS_PARAMETER = new Class[] { java.util.List.class };
    052
    053    /** For logging. Each subclass gets its own log instance. */
    054    private final Log log = LogFactory.getLog(getClass());
    055
    056    /**
    057     * Private constructor so that no instances can be created.
    058     */
    059    private DefaultBeanIntrospector() {
    060    }
    061
    062    /**
    063     * This method fixes an issue where IndexedPropertyDescriptor behaves differently in different versions of the JDK for 'indexed' properties which use
    064     * java.util.List (rather than an array). It implements a workaround for Bug 28358. If you have a Bean with the following getters/setters for an indexed
    065     * property:
    066     *
    067     * <pre>
    068     * public List getFoo()
    069     * public Object getFoo(int index)
    070     * public void setFoo(List foo)
    071     * public void setFoo(int index, Object foo)
    072     * </pre>
    073     *
    074     * then the IndexedPropertyDescriptor's getReadMethod() and getWriteMethod() behave as follows:
    075     * <ul>
    076     * <li>JDK 1.3.1_04: returns valid Method objects from these methods.</li>
    077     * <li>JDK 1.4.2_05: returns null from these methods.</li>
    078     * </ul>
    079     *
    080     * @param beanClass   the current class to be inspected
    081     * @param descriptors the array with property descriptors
    082     */
    083    private void handleIndexedPropertyDescriptors(final Class<?> beanClass, final PropertyDescriptor[] descriptors) {
    084        for (final PropertyDescriptor pd : descriptors) {
    085            if (pd instanceof IndexedPropertyDescriptor) {
    086                final IndexedPropertyDescriptor descriptor = (IndexedPropertyDescriptor) pd;
    087                final String propName = descriptor.getName().substring(0, 1).toUpperCase() + descriptor.getName().substring(1);
    088
    089                if (descriptor.getReadMethod() == null) {
    090                    final String methodName = descriptor.getIndexedReadMethod() != null ? descriptor.getIndexedReadMethod().getName() : "get" + propName;
    091                    final Method readMethod = MethodUtils.getMatchingAccessibleMethod(beanClass, methodName, BeanUtils.EMPTY_CLASS_ARRAY);
    092                    if (readMethod != null) {
    093                        try {
    094                            descriptor.setReadMethod(readMethod);
    095                        } catch (final Exception e) {
    096                            log.error("Error setting indexed property read method", e);
    097                        }
    098                    }
    099                }
    100                if (descriptor.getWriteMethod() == null) {
    101                    final String methodName = descriptor.getIndexedWriteMethod() != null ? descriptor.getIndexedWriteMethod().getName() : "set" + propName;
    102                    Method writeMethod = MethodUtils.getMatchingAccessibleMethod(beanClass, methodName, LIST_CLASS_PARAMETER);
    103                    if (writeMethod == null) {
    104                        for (final Method m : beanClass.getMethods()) {
    105                            if (m.getName().equals(methodName)) {
    106                                final Class<?>[] parameterTypes = m.getParameterTypes();
    107                                if (parameterTypes.length == 1 && List.class.isAssignableFrom(parameterTypes[0])) {
    108                                    writeMethod = m;
    109                                    break;
    110                                }
    111                            }
    112                        }
    113                    }
    114                    if (writeMethod != null) {
    115                        try {
    116                            descriptor.setWriteMethod(writeMethod);
    117                        } catch (final Exception e) {
    118                            log.error("Error setting indexed property write method", e);
    119                        }
    120                    }
    121                }
    122            }
    123        }
    124    }
    125
    126    /**
    127     * Performs introspection of a specific Java class. This implementation uses the {@code java.beans.Introspector.getBeanInfo()} method to obtain all property
    128     * descriptors for the current class and adds them to the passed in introspection context.
    129     *
    130     * @param icontext the introspection context
    131     */
    132    @Override
    133    public void introspect(final IntrospectionContext icontext) {
    134        BeanInfo beanInfo = null;
    135        try {
    136            beanInfo = Introspector.getBeanInfo(icontext.getTargetClass());
    137        } catch (final IntrospectionException e) {
    138            // no descriptors are added to the context
    139            log.error("Error when inspecting class " + icontext.getTargetClass(), e);
    140            return;
    141        }
    142
    143        PropertyDescriptor[] descriptors = beanInfo.getPropertyDescriptors();
    144        if (descriptors == null) {
    145            descriptors = PropertyDescriptors.EMPTY_ARRAY;
    146        }
    147
    148        handleIndexedPropertyDescriptors(icontext.getTargetClass(), descriptors);
    149        icontext.addPropertyDescriptors(descriptors);
    150    }
    151}