    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.configuration2.beanutils;
    018
    019import java.beans.PropertyDescriptor;
    020import java.lang.reflect.InvocationTargetException;
    021import java.util.ArrayList;
    022import java.util.Collection;
    023import java.util.Collections;
    024import java.util.HashMap;
    025import java.util.List;
    026import java.util.Map;
    027import java.util.Set;
    028import java.util.TreeSet;
    029
    030import org.apache.commons.beanutils.BeanUtilsBean;
    031import org.apache.commons.beanutils.ConvertUtilsBean;
    032import org.apache.commons.beanutils.DynaBean;
    033import org.apache.commons.beanutils.FluentPropertyBeanIntrospector;
    034import org.apache.commons.beanutils.PropertyUtilsBean;
    035import org.apache.commons.beanutils.WrapDynaBean;
    036import org.apache.commons.beanutils.WrapDynaClass;
    037import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    038import org.apache.commons.lang3.ClassUtils;
    039
    040/**
    041 * <p>
    042 * A helper class for creating bean instances that are defined in configuration files.
    043 * </p>
    044 * <p>
    045 * This class provides utility methods related to bean creation operations. These methods simplify such operations
    046 * because a client need not deal with all involved interfaces. Usually, if a bean declaration has already been
    047 * obtained, a single method call is necessary to create a new bean instance.
    048 * </p>
    049 * <p>
    050 * This class also supports the registration of custom bean factories. Implementations of the {@link BeanFactory}
    051 * interface can be registered under a symbolic name using the {@code registerBeanFactory()} method. In the
    052 * configuration file the name of the bean factory can be specified in the bean declaration. Then this factory will be
    053 * used to create the bean.
    054 * </p>
    055 * <p>
    056 * In order to create beans using {@code BeanHelper}, create and instance of this class and initialize it accordingly -
    057 * a default {@link BeanFactory} can be passed to the constructor, and additional bean factories can be registered (see
    058 * above). Then this instance can be used to create beans from {@link BeanDeclaration} objects. {@code BeanHelper} is
    059 * thread-safe. So an instance can be passed around in an application and shared between multiple components.
    060 * </p>
    061 *
    062 * @since 1.3
    063 */
    064public final class BeanHelper {
    065
    066    /**
    067     * A default instance of {@code BeanHelper} which can be shared between arbitrary components. If no special
    068     * configuration is needed, this instance can be used throughout an application. Otherwise, new instances can be created
    069     * with their own configuration.
    070     */
    071    public static final BeanHelper INSTANCE = new BeanHelper();
    072
    073    /**
    074     * A special instance of {@code BeanUtilsBean} which is used for all property set and copy operations. This instance was
    075     * initialized with {@code BeanIntrospector} objects which support fluent interfaces. This is required for handling
    076     * builder parameter objects correctly.
    077     */
    078    private static final BeanUtilsBean BEAN_UTILS_BEAN = initBeanUtilsBean();
    079
    080    /** Stores a map with the registered bean factories. */
    081    private final Map<String, BeanFactory> beanFactories = Collections.synchronizedMap(new HashMap<>());
    082
    083    /**
    084     * Stores the default bean factory, which is used if no other factory is provided in a bean declaration.
    085     */
    086    private final BeanFactory defaultBeanFactory;
    087
    088    /**
    089     * Constructs a new instance of {@code BeanHelper} with the default instance of {@link DefaultBeanFactory} as default
    090     * {@link BeanFactory}.
    091     */
    092    public BeanHelper() {
    093        this(null);
    094    }
    095
    096    /**
    097     * Constructs a new instance of {@code BeanHelper} and sets the specified default {@code BeanFactory}.
    098     *
    099     * @param defaultBeanFactory the default {@code BeanFactory} (can be <b>null</b>, then a default instance is used)
    100     */
    101    public BeanHelper(final BeanFactory defaultBeanFactory) {
    102        this.defaultBeanFactory = defaultBeanFactory != null ? defaultBeanFactory : DefaultBeanFactory.INSTANCE;
    103    }
    104
    105    /**
    106     * Registers a bean factory under a symbolic name. This factory object can then be specified in bean declarations with
    107     * the effect that this factory will be used to obtain an instance for the corresponding bean declaration.
    108     *
    109     * @param name the name of the factory
    110     * @param factory the factory to be registered
    111     */
    112    public void registerBeanFactory(final String name, final BeanFactory factory) {
    113        if (name == null) {
    114            throw new IllegalArgumentException("Name for bean factory must not be null!");
    115        }
    116        if (factory == null) {
    117            throw new IllegalArgumentException("Bean factory must not be null!");
    118        }
    119
    120        beanFactories.put(name, factory);
    121    }
    122
    123    /**
    124     * Deregisters the bean factory with the given name. After that this factory cannot be used any longer.
    125     *
    126     * @param name the name of the factory to be deregistered
    127     * @return the factory that was registered under this name; <b>null</b> if there was no such factory
    128     */
    129    public BeanFactory deregisterBeanFactory(final String name) {
    130        return beanFactories.remove(name);
    131    }
    132
    133    /**
    134     * Gets a set with the names of all currently registered bean factories.
    135     *
    136     * @return a set with the names of the registered bean factories
    137     */
    138    public Set<String> registeredFactoryNames() {
    139        return beanFactories.keySet();
    140    }
    141
    142    /**
    143     * Gets the default bean factory.
    144     *
    145     * @return the default bean factory
    146     */
    147    public BeanFactory getDefaultBeanFactory() {
    148        return defaultBeanFactory;
    149    }
    150
    151    /**
    152     * Initializes the passed in bean. This method will obtain all the bean's properties that are defined in the passed in
    153     * bean declaration. These properties will be set on the bean. If necessary, further beans will be created recursively.
    154     *
    155     * @param bean the bean to be initialized
    156     * @param data the bean declaration
    157     * @throws ConfigurationRuntimeException if a property cannot be set
    158     */
    159    public void initBean(final Object bean, final BeanDeclaration data) {
    160        initBeanProperties(bean, data);
    161
    162        final Map<String, Object> nestedBeans = data.getNestedBeanDeclarations();
    163        if (nestedBeans != null) {
    164            if (bean instanceof Collection) {
    165                // This is safe because the collection stores the values of the
    166                // nested beans.
    167                @SuppressWarnings("unchecked")
    168                final Collection<Object> coll = (Collection<Object>) bean;
    169                if (nestedBeans.size() == 1) {
    170                    final Map.Entry<String, Object> e = nestedBeans.entrySet().iterator().next();
    171                    final String propName = e.getKey();
    172                    final Class<?> defaultClass = getDefaultClass(bean, propName);
    173                    if (e.getValue() instanceof List) {
    174                        // This is safe, provided that the bean declaration is implemented
    175                        // correctly.
    176                        @SuppressWarnings("unchecked")
    177                        final List<BeanDeclaration> decls = (List<BeanDeclaration>) e.getValue();
    178                        decls.forEach(decl -> coll.add(createBean(decl, defaultClass)));
    179                    } else {
    180                        coll.add(createBean((BeanDeclaration) e.getValue(), defaultClass));
    181                    }
    182                }
    183            } else {
    184                nestedBeans.forEach((propName, prop) -> {
    185                    final Class<?> defaultClass = getDefaultClass(bean, propName);
    186                    if (prop instanceof Collection) {
    187                        final Collection<Object> beanCollection = createPropertyCollection(propName, defaultClass);
    188                        ((Collection<BeanDeclaration>) prop).forEach(elemDef -> beanCollection.add(createBean(elemDef)));
    189                        initProperty(bean, propName, beanCollection);
    190                    } else {
    191                        initProperty(bean, propName, createBean((BeanDeclaration) prop, defaultClass));
    192                    }
    193                });
    194            }
    195        }
    196    }
    197
    198    /**
    199     * Initializes the beans properties.
    200     *
    201     * @param bean the bean to be initialized
    202     * @param data the bean declaration
    203     * @throws ConfigurationRuntimeException if a property cannot be set
    204     */
    205    public static void initBeanProperties(final Object bean, final BeanDeclaration data) {
    206        final Map<String, Object> properties = data.getBeanProperties();
    207        if (properties != null) {
    208            properties.forEach((k, v) -> initProperty(bean, k, v));
    209        }
    210    }
    211
    212    /**
    213     * Creates a {@code DynaBean} instance which wraps the passed in bean.
    214     *
    215     * @param bean the bean to be wrapped (must not be <b>null</b>)
    216     * @return a {@code DynaBean} wrapping the passed in bean
    217     * @throws IllegalArgumentException if the bean is <b>null</b>
    218     * @since 2.0
    219     */
    220    public static DynaBean createWrapDynaBean(final Object bean) {
    221        if (bean == null) {
    222            throw new IllegalArgumentException("Bean must not be null!");
    223        }
    224        final WrapDynaClass dynaClass = WrapDynaClass.createDynaClass(bean.getClass(), BEAN_UTILS_BEAN.getPropertyUtils());
    225        return new WrapDynaBean(bean, dynaClass);
    226    }
    227
    228    /**
    229     * Copies matching properties from the source bean to the destination bean using a specially configured
    230     * {@code PropertyUtilsBean} instance. This method ensures that enhanced introspection is enabled when doing the copy
    231     * operation.
    232     *
    233     * @param dest the destination bean
    234     * @param orig the source bean
    235     * @throws NoSuchMethodException exception thrown by {@code PropertyUtilsBean}
    236     * @throws InvocationTargetException exception thrown by {@code PropertyUtilsBean}
    237     * @throws IllegalAccessException exception thrown by {@code PropertyUtilsBean}
    238     * @since 2.0
    239     */
    240    public static void copyProperties(final Object dest, final Object orig) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException {
    241        BEAN_UTILS_BEAN.getPropertyUtils().copyProperties(dest, orig);
    242    }
    243
    244    /**
    245     * Gets the Class of the property if it can be determined.
    246     *
    247     * @param bean The bean containing the property.
    248     * @param propName The name of the property.
    249     * @return The class associated with the property or null.
    250     */
    251    private static Class<?> getDefaultClass(final Object bean, final String propName) {
    252        try {
    253            final PropertyDescriptor desc = BEAN_UTILS_BEAN.getPropertyUtils().getPropertyDescriptor(bean, propName);
    254            if (desc == null) {
    255                return null;
    256            }
    257            return desc.getPropertyType();
    258        } catch (final Exception ex) {
    259            return null;
    260        }
    261    }
    262
    263    /**
    264     * Sets a property on the given bean using Common Beanutils.
    265     *
    266     * @param bean the bean
    267     * @param propName the name of the property
    268     * @param value the property's value
    269     * @throws ConfigurationRuntimeException if the property is not writable or an error occurred
    270     */
    271    private static void initProperty(final Object bean, final String propName, final Object value) {
    272        if (!isPropertyWriteable(bean, propName)) {
    273            throw new ConfigurationRuntimeException("Property " + propName + " cannot be set on " + bean.getClass().getName());
    274        }
    275
    276        try {
    277            BEAN_UTILS_BEAN.setProperty(bean, propName, value);
    278        } catch (final IllegalAccessException | InvocationTargetException itex) {
    279            throw new ConfigurationRuntimeException(itex);
    280        }
    281    }
    282
    283    /**
    284     * Creates a concrete collection instance to populate a property of type collection. This method tries to guess an
    285     * appropriate collection type. Mostly the type of the property will be one of the collection interfaces rather than a
    286     * concrete class; so we have to create a concrete equivalent.
    287     *
    288     * @param propName the name of the collection property
    289     * @param propertyClass the type of the property
    290     * @return the newly created collection
    291     */
    292    private static Collection<Object> createPropertyCollection(final String propName, final Class<?> propertyClass) {
    293        final Collection<Object> beanCollection;
    294
    295        if (List.class.isAssignableFrom(propertyClass)) {
    296            beanCollection = new ArrayList<>();
    297        } else if (Set.class.isAssignableFrom(propertyClass)) {
    298            beanCollection = new TreeSet<>();
    299        } else {
    300            throw new UnsupportedOperationException("Unable to handle collection of type : " + propertyClass.getName() + " for property " + propName);
    301        }
    302        return beanCollection;
    303    }
    304
    305    /**
    306     * Sets a property on the bean only if the property exists
    307     *
    308     * @param bean the bean
    309     * @param propName the name of the property
    310     * @param value the property's value
    311     * @throws ConfigurationRuntimeException if the property is not writable or an error occurred
    312     */
    313    public static void setProperty(final Object bean, final String propName, final Object value) {
    314        if (isPropertyWriteable(bean, propName)) {
    315            initProperty(bean, propName, value);
    316        }
    317    }
    318
    319    /**
    320     * The main method for creating and initializing beans from a configuration. This method will return an initialized
    321     * instance of the bean class specified in the passed in bean declaration. If this declaration does not contain the
    322     * class of the bean, the passed in default class will be used. From the bean declaration the factory to be used for
    323     * creating the bean is queried. The declaration may here return <b>null</b>, then a default factory is used. This
    324     * factory is then invoked to perform the create operation.
    325     *
    326     * @param data the bean declaration
    327     * @param defaultClass the default class to use
    328     * @param param an additional parameter that will be passed to the bean factory; some factories may support parameters
    329     *        and behave different depending on the value passed in here
    330     * @return the new bean
    331     * @throws ConfigurationRuntimeException if an error occurs
    332     */
    333    public Object createBean(final BeanDeclaration data, final Class<?> defaultClass, final Object param) {
    334        if (data == null) {
    335            throw new IllegalArgumentException("Bean declaration must not be null!");
    336        }
    337
    338        final BeanFactory factory = fetchBeanFactory(data);
    339        final BeanCreationContext bcc = createBeanCreationContext(data, defaultClass, param, factory);
    340        try {
    341            return factory.createBean(bcc);
    342        } catch (final Exception ex) {
    343            throw new ConfigurationRuntimeException(ex);
    344        }
    345    }
    346
    347    /**
    348     * Creates a bean instance for the specified declaration. This method is a short cut for
    349     * {@code createBean(data, null, null);}.
    350     *
    351     * @param data the bean declaration
    352     * @param defaultClass the class to be used when in the declaration no class is specified
    353     * @return the new bean
    354     * @throws ConfigurationRuntimeException if an error occurs
    355     */
    356    public Object createBean(final BeanDeclaration data, final Class<?> defaultClass) {
    357        return createBean(data, defaultClass, null);
    358    }
    359
    360    /**
    361     * Creates a bean instance for the specified declaration. This method is a short cut for
    362     * {@code createBean(data, null);}.
    363     *
    364     * @param data the bean declaration
    365     * @return the new bean
    366     * @throws ConfigurationRuntimeException if an error occurs
    367     */
    368    public Object createBean(final BeanDeclaration data) {
    369        return createBean(data, null);
    370    }
    371
    372    /**
    373     * Loads a {@code java.lang.Class} object for the specified name. Because class loading can be tricky in some
    374     * environments the code for retrieving a class by its name was extracted into this helper method. So if changes are
    375     * necessary, they can be made at a single place.
    376     *
    377     * @param name the name of the class to be loaded
    378     * @return the class object for the specified name
    379     * @throws ClassNotFoundException if the class cannot be loaded
    380     */
    381    static Class<?> loadClass(final String name) throws ClassNotFoundException {
    382        return ClassUtils.getClass(name);
    383    }
    384
    385    /**
    386     * Tests whether the specified property of the given bean instance supports write access.
    387     *
    388     * @param bean the bean instance
    389     * @param propName the name of the property in question
    390     * @return <b>true</b> if this property can be written, <b>false</b> otherwise
    391     */
    392    private static boolean isPropertyWriteable(final Object bean, final String propName) {
    393        return BEAN_UTILS_BEAN.getPropertyUtils().isWriteable(bean, propName);
    394    }
    395
    396    /**
    397     * Determines the class of the bean to be created. If the bean declaration contains a class name, this class is used.
    398     * Otherwise it is checked whether a default class is provided. If this is not the case, the factory's default class is
    399     * used. If this class is undefined, too, an exception is thrown.
    400     *
    401     * @param data the bean declaration
    402     * @param defaultClass the default class
    403     * @param factory the bean factory to use
    404     * @return the class of the bean to be created
    405     * @throws ConfigurationRuntimeException if the class cannot be determined
    406     */
    407    private static Class<?> fetchBeanClass(final BeanDeclaration data, final Class<?> defaultClass, final BeanFactory factory) {
    408        final String clsName = data.getBeanClassName();
    409        if (clsName != null) {
    410            try {
    411                return loadClass(clsName);
    412            } catch (final ClassNotFoundException cex) {
    413                throw new ConfigurationRuntimeException(cex);
    414            }
    415        }
    416
    417        if (defaultClass != null) {
    418            return defaultClass;
    419        }
    420
    421        final Class<?> clazz = factory.getDefaultBeanClass();
    422        if (clazz == null) {
    423            throw new ConfigurationRuntimeException("Bean class is not specified!");
    424        }
    425        return clazz;
    426    }
    427
    428    /**
    429     * Obtains the bean factory to use for creating the specified bean. This method will check whether a factory is
    430     * specified in the bean declaration. If this is not the case, the default bean factory will be used.
    431     *
    432     * @param data the bean declaration
    433     * @return the bean factory to use
    434     * @throws ConfigurationRuntimeException if the factory cannot be determined
    435     */
    436    private BeanFactory fetchBeanFactory(final BeanDeclaration data) {
    437        final String factoryName = data.getBeanFactoryName();
    438        if (factoryName != null) {
    439            final BeanFactory factory = beanFactories.get(factoryName);
    440            if (factory == null) {
    441                throw new ConfigurationRuntimeException("Unknown bean factory: " + factoryName);
    442            }
    443            return factory;
    444        }
    445        return getDefaultBeanFactory();
    446    }
    447
    448    /**
    449     * Creates a {@code BeanCreationContext} object for the creation of the specified bean.
    450     *
    451     * @param data the bean declaration
    452     * @param defaultClass the default class to use
    453     * @param param an additional parameter that will be passed to the bean factory; some factories may support parameters
    454     *        and behave different depending on the value passed in here
    455     * @param factory the current bean factory
    456     * @return the {@code BeanCreationContext}
    457     * @throws ConfigurationRuntimeException if the bean class cannot be determined
    458     */
    459    private BeanCreationContext createBeanCreationContext(final BeanDeclaration data, final Class<?> defaultClass, final Object param,
    460        final BeanFactory factory) {
    461        final Class<?> beanClass = fetchBeanClass(data, defaultClass, factory);
    462        return new BeanCreationContextImpl(this, beanClass, data, param);
    463    }
    464
    465    /**
    466     * Initializes the shared {@code BeanUtilsBean} instance. This method sets up custom bean introspection in a way that
    467     * fluent parameter interfaces are supported.
    468     *
    469     * @return the {@code BeanUtilsBean} instance to be used for all property set operations
    470     */
    471    private static BeanUtilsBean initBeanUtilsBean() {
    472        final PropertyUtilsBean propUtilsBean = new PropertyUtilsBean();
    473        propUtilsBean.addBeanIntrospector(new FluentPropertyBeanIntrospector());
    474        return new BeanUtilsBean(new ConvertUtilsBean(), propUtilsBean);
    475    }
    476
    477    /**
    478     * An implementation of the {@code BeanCreationContext} interface used by {@code BeanHelper} to communicate with a
    479     * {@code BeanFactory}. This class contains all information required for the creation of a bean. The methods for
    480     * creating and initializing bean instances are implemented by calling back to the provided {@code BeanHelper} instance
    481     * (which is the instance that created this object).
    482     */
    483    private static final class BeanCreationContextImpl implements BeanCreationContext {
    484        /** The association BeanHelper instance. */
    485        private final BeanHelper beanHelper;
    486
    487        /** The class of the bean to be created. */
    488        private final Class<?> beanClass;
    489
    490        /** The underlying bean declaration. */
    491        private final BeanDeclaration data;
    492
    493        /** The parameter for the bean factory. */
    494        private final Object param;
    495
    496        private BeanCreationContextImpl(final BeanHelper helper, final Class<?> beanClass, final BeanDeclaration data, final Object param) {
    497            beanHelper = helper;
    498            this.beanClass = beanClass;
    499            this.param = param;
    500            this.data = data;
    501        }
    502
    503        @Override
    504        public void initBean(final Object bean, final BeanDeclaration data) {
    505            beanHelper.initBean(bean, data);
    506        }
    507
    508        @Override
    509        public Object getParameter() {
    510            return param;
    511        }
    512
    513        @Override
    514        public BeanDeclaration getBeanDeclaration() {
    515            return data;
    516        }
    517
    518        @Override
    519        public Class<?> getBeanClass() {
    520            return beanClass;
    521        }
    522
    523        @Override
    524        public Object createBean(final BeanDeclaration data) {
    525            return beanHelper.createBean(data);
    526        }
    527    }
    528}