/*
 * Copyright 2002-2007 the original author or authors.
 *
 * Licensed 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.springframework.web.portlet.mvc;

import javax.portlet.ActionRequest;
import javax.portlet.PortletException;
import javax.portlet.PortletRequest;
import javax.portlet.PortletSession;
import javax.portlet.RenderRequest;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.PropertyEditorRegistrar;
import org.springframework.validation.BindException;
import org.springframework.validation.BindingErrorProcessor;
import org.springframework.validation.MessageCodesResolver;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
import org.springframework.web.bind.support.WebBindingInitializer;
import org.springframework.web.portlet.bind.PortletRequestDataBinder;
import org.springframework.web.portlet.context.PortletWebRequest;
import org.springframework.web.portlet.handler.PortletSessionRequiredException;

/**
 * <p>Controller implementation which creates an object (the command object) on
 * receipt of a request and attempts to populate this object with request parameters.</p>
 *
 * <p>This controller is the base for all controllers wishing to populate
 * JavaBeans based on request parameters, validate the content of such
 * JavaBeans using {@link Validator Validators} and use custom editors (in the form of
 * {@link java.beans.PropertyEditor PropertyEditors}) to transform 
 * objects into strings and vice versa, for example. Three notions are mentioned here:</p>
 *
 * <p><b>Command class:</b><br>
 * An instance of the command class will be created for each request and populated
 * with request parameters. A command class can basically be any Java class; the only
 * requirement is a no-arg constructor. The command class should preferably be a
 * JavaBean in order to be able to populate bean properties with request parameters.</p>
 *
 * <p><b>Populating using request parameters and PropertyEditors:</b><br>
 * Upon receiving a request, any BaseCommandController will attempt to fill the
 * command object using the request parameters. This is done using the typical
 * and well-known JavaBeans property notation. When a request parameter named
 * <code>'firstName'</code> exists, the framework will attempt to call 
 * <code>setFirstName([value])</code> passing the value of the parameter. Nested properties
 * are of course supported. For instance a parameter named <code>'address.city'</code>
 * will result in a <code>getAddress().setCity([value])</code> call on the
 * command class.</p>
 *
 * <p>It's important to realize that you are not limited to String arguments in
 * your JavaBeans. Using the PropertyEditor-notion as supplied by the
 * java.beans package, you will be able to transform Strings to Objects and
 * the other way around. For instance <code>setLocale(Locale loc)</code> is
 * perfectly possible for a request parameter named <code>locale</code> having
 * a value of <code>en</code>, as long as you register the appropriate
 * PropertyEditor in the Controller (see {@link #initBinder initBinder()}
 * for more information on that matter).</p>
 *
 * <p><b>Validators:</b>
 * After the controller has successfully populated the command object with
 * parameters from the request, it will use any configured validators to
 * validate the object. Validation results will be put in a
 * {@link org.springframework.validation.Errors Errors} object which can be
 * used in a View to render any input problems.</p>
 *
 * <p><b><a name="workflow">Workflow
 * (<a href="AbstractController.html#workflow">and that defined by superclass</a>):</b><br>
 * Since this class is an abstract base class for more specific implementation,
 * it does not override the <code>handleRequestInternal()</code> methods and also has no
 * actual workflow. Implementing classes like
 * {@link AbstractFormController AbstractFormController},
 * {@link AbstractCommandController AbstractCommandController},
 * {@link SimpleFormController SimpleFormController} and
 * {@link AbstractWizardFormController AbstractWizardFormController}
 * provide actual functionality and workflow.
 * More information on workflow performed by superclasses can be found
 * <a href="AbstractController.html#workflow">here</a>.</p>
 *
 * <p><b><a name="config">Exposed configuration properties</a>
 * (<a href="AbstractController.html#config">and those defined by superclass</a>):</b><br>
 * <table border="1">
 *  <tr>
 *      <td><b>name</b></th>
 *      <td><b>default</b></td>
 *      <td><b>description</b></td>
 *  </tr>
 *  <tr>
 *      <td>commandName</td>
 *      <td>command</td>
 *      <td>the name to use when binding the instantiated command class
 *          to the request</td>
 *  </tr>
 *  <tr>
 *      <td>commandClass</td>
 *      <td><i>null</i></td>
 *      <td>the class to use upon receiving a request and which to fill
 *          using the request parameters. What object is used and whether
 *          or not it should be created is defined by extending classes
 *          and their configuration properties and methods.</td>
 *  </tr>
 *  <tr>
 *      <td>validators</td>
 *      <td><i>null</i></td>
 *      <td>Array of Validator beans. The validator will be called at appropriate
 *          places in the workflow of subclasses (have a look at those for more info)
 *          to validate the command object.</td>
 *  </tr>
 *  <tr>
 *      <td>validator</td>
 *      <td><i>null</i></td>
 *      <td>Short-form property for setting only one Validator bean (usually passed in
 *          using a &lt;ref bean="beanId"/&gt; property.</td>
 *  </tr>
 *  <tr>
 *      <td>validateOnBinding</td>
 *      <td>true</td>
 *      <td>Indicates whether or not to validate the command object after the
 *          object has been populated with request parameters.</td>
 *  </tr>
 * </table>
 * </p>
 *
 * <p>Thanks to Rainer Schmitz and Nick Lothian for their suggestions!
 *
 * @author Juergen Hoeller
 * @author John A. Lewis
 * @since 2.0
 */
public abstract class BaseCommandController extends AbstractController {

	/**
	 * Unlike the Servlet version of these classes, we have to deal with the
	 * two-phase nature of the porlet request. To do this, we need to pass
	 * forward the command object and the bind/validation errors that occured
	 * on the command object from the action phase to the render phase.
	 * The only direct way to pass things forward and preserve them for each
	 * render request is through render parameters, but these are limited to
	 * String objects and we need to pass more complicated objects. The only
	 * other way to do this is in the session. The bad thing about using the
	 * session is that we have no way of knowing when we are done re-rendering
	 * the request and so we don't know when we can remove the objects from
	 * the session. So we will end up polluting the session with old objects
	 * when we finally leave the render of this controller and move on to 
	 * somthing else. To minimize the pollution, we will use a static string
	 * value as the session attribute name. At least this way we are only ever
	 * leaving one orphaned set behind. The methods that return these names
	 * can be overridden if you want to use a different method, but be aware
	 * of the session pollution that may occur.
	 */
	private static final String RENDER_COMMAND_SESSION_ATTRIBUTE = 
			"org.springframework.web.portlet.mvc.RenderCommand";

	private static final String RENDER_ERRORS_SESSION_ATTRIBUTE =
			"org.springframework.web.portlet.mvc.RenderErrors";

	public static final String DEFAULT_COMMAND_NAME = "command";


	private String commandName = DEFAULT_COMMAND_NAME;
	
	private Class commandClass;
	
	private Validator[] validators;
	
	private boolean validateOnBinding = true;
	
	private MessageCodesResolver messageCodesResolver;

	private BindingErrorProcessor bindingErrorProcessor;

	private PropertyEditorRegistrar[] propertyEditorRegistrars;

	private WebBindingInitializer webBindingInitializer;


	/**
	 * Set the name of the command in the model.
	 * The command object will be included in the model under this name.
	 */
	public final void setCommandName(String commandName) {
		this.commandName = commandName;
	}

	/**
	 * Return the name of the command in the model.
	 */
	public final String getCommandName() {
		return this.commandName;
	}

	/**
	 * Set the command class for this controller.
	 * An instance of this class gets populated and validated on each request.
	 */
	public final void setCommandClass(Class commandClass) {
		this.commandClass = commandClass;
	}

	/**
	 * Return the command class for this controller.
	 */
	public final Class getCommandClass() {
		return this.commandClass;
	}

	/**
	 * Set the primary Validator for this controller. The Validator
	 * must support the specified command class. If there are one
	 * or more existing validators set already when this method is
	 * called, only the specified validator will be kept. Use
	 * {@link #setValidators(Validator[])} to set multiple validators.
	 */
	public final void setValidator(Validator validator) {
		this.validators = new Validator[] {validator};
	}

	/**
	 * @return the primary Validator for this controller.
	 */
	public final Validator getValidator() {
		return (this.validators != null && this.validators.length > 0 ? this.validators[0] : null);
	}

	/**
	 * Set the Validators for this controller.
	 * The Validator must support the specified command class.
	 */
	public final void setValidators(Validator[] validators) {
		this.validators = validators;
	}

	/**
	 * Return the Validators for this controller.
	 */
	public final Validator[] getValidators() {
		return this.validators;
	}

	/**
	 * Set if the Validator should get applied when binding.
	 */
	public final void setValidateOnBinding(boolean validateOnBinding) {
		this.validateOnBinding = validateOnBinding;
	}

	/**
	 * Return if the Validator should get applied when binding.
	 */
	public final boolean isValidateOnBinding() {
		return this.validateOnBinding;
	}

	/**
	 * Set the strategy to use for resolving errors into message codes.
	 * Applies the given strategy to all data binders used by this controller.
	 * <p>Default is null, i.e. using the default strategy of the data binder.
	 * @see #createBinder
	 * @see org.springframework.validation.DataBinder#setMessageCodesResolver
	 */
	public final void setMessageCodesResolver(MessageCodesResolver messageCodesResolver) {
		this.messageCodesResolver = messageCodesResolver;
	}

	/**
	 * Return the strategy to use for resolving errors into message codes (if any).
	 */
	public final MessageCodesResolver getMessageCodesResolver() {
		return this.messageCodesResolver;
	}

	/**
	 * Set the strategy to use for processing binding errors, that is,
	 * required field errors and <code>PropertyAccessException</code>s.
	 * <p>Default is <code>null</code>, i.e. using the default strategy of
	 * the data binder.
	 * @see #createBinder
	 * @see org.springframework.validation.DataBinder#setBindingErrorProcessor
	 */
	public final void setBindingErrorProcessor(BindingErrorProcessor bindingErrorProcessor) {
		this.bindingErrorProcessor = bindingErrorProcessor;
	}

	/**
	 * Return the strategy to use for processing binding errors (if any).
	 */
	public final BindingErrorProcessor getBindingErrorProcessor() {
		return this.bindingErrorProcessor;
	}

	/**
	 * Specify a single PropertyEditorRegistrar to be applied
	 * to every DataBinder that this controller uses.
	 * <p>Allows for factoring out the registration of PropertyEditors
	 * to separate objects, as an alternative to <code>initBinder</code>.
	 * @see #initBinder
	 */
	public final void setPropertyEditorRegistrar(PropertyEditorRegistrar propertyEditorRegistrar) {
		this.propertyEditorRegistrars = new PropertyEditorRegistrar[] {propertyEditorRegistrar};
	}

	/**
	 * Specify one or more PropertyEditorRegistrars to be applied
	 * to every DataBinder that this controller uses.
	 * <p>Allows for factoring out the registration of PropertyEditors
	 * to separate objects, as alternative to <code>initBinder</code>.
	 * @see #initBinder
	 */
	public final void setPropertyEditorRegistrars(PropertyEditorRegistrar[] propertyEditorRegistrars) {
		this.propertyEditorRegistrars = propertyEditorRegistrars;
	}

	/**
	 * Return the PropertyEditorRegistrars (if any) to be applied
	 * to every DataBinder that this controller uses.
	 */
	public final PropertyEditorRegistrar[] getPropertyEditorRegistrars() {
		return this.propertyEditorRegistrars;
	}