core/src/main/java/org/apache/struts/action/DynaActionFormClass.java

/*
 * $Id$
 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.struts.action;

import org.apache.commons.beanutils.DynaBean;
import org.apache.commons.beanutils.DynaClass;
import org.apache.commons.beanutils.DynaProperty;
import org.apache.struts.config.FormBeanConfig;
import org.apache.struts.config.FormPropertyConfig;
import org.apache.struts.util.RequestUtils;

import java.io.Serializable;

import java.util.HashMap;

/**
 * <p>Implementation of <code>DynaClass</code> for <code>DynaActionForm</code>
 * classes that allow developers to define ActionForms without having to
 * individually code all of the classes. <strong>NOTE</strong> - This class is
 * only used in the internal implementation of dynamic action form beans.
 * Application developers never need to consult this documentation.</p>
 *
 * @version $Rev$ $Date: 2006-01-17 07:26:20 -0500 (Tue, 17 Jan 2006)
 *          $
 * @since Struts 1.1
 */
public class DynaActionFormClass implements DynaClass, Serializable {
    // ----------------------------------------------------- Instance Variables

    /**
     * <p>The <code>DynaActionForm</code> implementation <code>Class</code>
     * which we will use to create new bean instances.</p>
     */
    protected transient Class beanClass = null;

    /**
     * <p>The form bean configuration information for this class.</p>
     */
    protected FormBeanConfig config = null;

    /**
     * <p>The "dynamic class name" for this <code>DynaClass</code>.</p>
     */
    protected String name = null;

    /**
     * <p>The set of dynamic properties that are part of this DynaClass.</p>
     */
    protected DynaProperty[] properties = null;

    /**
     * <p>The set of dynamic properties that are part of this
     * <code>DynaClass</code>, keyed by the property name.  Individual
     * descriptor instances will be the same instances as those in the
     * <code>properties</code> list.
     */
    protected HashMap propertiesMap = new HashMap();

    // ----------------------------------------------------------- Constructors

    /**
     * <p>Construct a new <code>DynaActionFormClass</code> for the specified
     * form bean configuration.  This constructor is private;
     * <code>DynaActionFormClass</code> instances will be created as needed
     * via calls to the static <code>createDynaActionFormClass()</code>
     * method.</p>
     *
     * @param config The FormBeanConfig instance describing the properties of
     *               the bean to be created
     * @throws IllegalArgumentException if the bean implementation class
     *                                  specified in the configuration is not
     *                                  DynaActionForm (or a subclass of
     *                                  DynaActionForm)
     */
    public DynaActionFormClass(FormBeanConfig config) {
        introspect(config);
    }

    // ------------------------------------------------------ DynaClass Methods

    /**
     * <p>Return the name of this <code>DynaClass</code> (analogous to the
     * <code>getName()</code> method of <code>java.lang.Class</code>, which
     * allows the same <code>DynaClass</code> implementation class to support
     * different dynamic classes, with different sets of properties.
     *
     * @return The name of this <code>DynaClass</code>.
     */
    public String getName() {
        return (this.name);
    }

    /**
     * <p>Return a property descriptor for the specified property, if it
     * exists; otherwise, return <code>null</code>.</p>
     *
     * @param name Name of the dynamic property for which a descriptor is
     *             requested
     * @return A property descriptor for the specified property.
     * @throws IllegalArgumentException if no property name is specified
     */
    public DynaProperty getDynaProperty(String name) {
        if (name == null) {
            throw new IllegalArgumentException("No property name specified");
        }

        return ((DynaProperty) propertiesMap.get(name));
    }

    /**
     * <p>Return an array of <code>DynaProperty</code>s for the properties
     * currently defined in this <code>DynaClass</code>.  If no properties are
     * defined, a zero-length array will be returned.</p>
     *
     * @return An array of property instances for this class.
     */
    public DynaProperty[] getDynaProperties() {
        return (properties);

        // :FIXME: Should we really be implementing
        // getBeanInfo instead, which returns property descriptors
        // and a bunch of other stuff?
    }

    /**
     * <p>Instantiate and return a new {@link DynaActionForm} instance,
     * associated with this <code>DynaActionFormClass</code>.  The properties
     * of the returned {@link DynaActionForm} will have been initialized to
     * the default values specified in the form bean configuration
     * information.</p>
     *
     * @return A new {@link DynaActionForm} instance.
     * @throws IllegalAccessException if the Class or the appropriate
     *                                constructor is not accessible
     * @throws InstantiationException if this Class represents an abstract
     *                                class, an array class, a primitive type,
     *                                or void; or if instantiation fails for
     *                                some other reason
     */
    public DynaBean newInstance()
        throws IllegalAccessException, InstantiationException {
        DynaActionForm dynaBean = (DynaActionForm) getBeanClass().newInstance();

        dynaBean.setDynaActionFormClass(this);

        FormPropertyConfig[] props = config.findFormPropertyConfigs();

        for (int i = 0; i < props.length; i++) {
            dynaBean.set(props[i].getName(), props[i].initial());
        }

        return (dynaBean);
    }

    // --------------------------------------------------------- Public Methods

    /**
     * <p>Render a <code>String</code> representation of this object.</p>
     *
     * @return The string representation of this instance.
     */
    public String toString() {
        StringBuffer sb = new StringBuffer("DynaActionFormBean[name=");

        sb.append(name);

        DynaProperty[] props = getDynaProperties();

        if (props == null) {
            props = new DynaProperty[0];
        }

        for (int i = 0; i < props.length; i++) {
            sb.append(',');
            sb.append(props[i].getName());
            sb.append('/');
            sb.append(props[i].getType());
        }

        sb.append("]");

        return (sb.toString());
    }

    // --------------------------------------------------------- Static Methods

    /**
     * Return the <code>DynaActionFormClass</code> instance for the specified
     * form bean configuration instance.
     *
     * @param config The config for which the class should be created.
     * @return The instance for the specified form bean config.
     */
    public static DynaActionFormClass createDynaActionFormClass(
        FormBeanConfig config) {
        return config.getDynaActionFormClass();
    }

    // ------------------------------------------------------ Protected Methods

    /**
     * <p>Return the implementation class we are using to construct new
     * instances, re-introspecting our {@link FormBeanConfig} if necessary
     * (that is, after being deserialized, since <code>beanClass</code> is
     * marked transient).</p>
     *
     * @return The implementation class used to construct new instances.
     */
    protected Class getBeanClass() {
        if (beanClass == null) {
            introspect(config);
        }

        return (beanClass);
    }

    /**
     * <p>Introspect our form bean configuration to identify the supported
     * properties.</p>
     *
     * @param config The FormBeanConfig instance describing the properties of
     *               the bean to be created
     * @throws IllegalArgumentException if the bean implementation class
     *                                  specified in the configuration is not
     *                                  DynaActionForm (or a subclass of
     *                                  DynaActionForm)
     */
    protected void introspect(FormBeanConfig config) {
        this.config = config;

        // Validate the ActionFormBean implementation class
        try {
            beanClass = RequestUtils.applicationClass(config.getType());
        } catch (Throwable t) {
            throw new IllegalArgumentException(
                "Cannot instantiate ActionFormBean class '" + config.getType()
                + "'", t);
        }

        if (!DynaActionForm.class.isAssignableFrom(beanClass)) {
            throw new IllegalArgumentException("Class '" + config.getType()
                + "' is not a subclass of "
                + "'org.apache.struts.action.DynaActionForm'");
        }

        // Set the name we will know ourselves by from the form bean name
        this.name = config.getName();

        // Look up the property descriptors for this bean class
        FormPropertyConfig[] descriptors = config.findFormPropertyConfigs();

        if (descriptors == null) {
            descriptors = new FormPropertyConfig[0];
        }

        // Create corresponding dynamic property definitions
        properties = new DynaProperty[descriptors.length];

        for (int i = 0; i < descriptors.length; i++) {
            properties[i] =
                new DynaProperty(descriptors[i].getName(),
                    descriptors[i].getTypeClass());
            propertiesMap.put(properties[i].getName(), properties[i]);
        }
    }

    // -------------------------------------------------------- Private Methods
}