/*
 * 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.servlet.view;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;

import org.springframework.beans.BeanUtils;
import org.springframework.core.Ordered;
import org.springframework.util.PatternMatchUtils;
import org.springframework.web.servlet.View;

/**
 * Simple implementation of the {@link org.springframework.web.servlet.ViewResolver}
 * interface, allowing for direct resolution of symbolic view names to URLs,
 * without explicit mapping definition. This is useful if your symbolic names
 * match the names of your view resources in a straightforward manner
 * (i.e. the symbolic name is the unique part of the resource's filename),
 * without the need for a dedicated mapping to be defined for each view.
 *
 * <p>Supports {@link AbstractUrlBasedView} subclasses like {@link InternalResourceView},
 * {@link org.springframework.web.servlet.view.velocity.VelocityView} and
 * {@link org.springframework.web.servlet.view.freemarker.FreeMarkerView}.
 * The view class for all views generated by this resolver can be specified
 * via the "viewClass" property.
 *
 * <p>View names can either be resource URLs themselves, or get augmented by a
 * specified prefix and/or suffix. Exporting an attribute that holds the
 * RequestContext to all views is explicitly supported.
 *
 * <p>Example: prefix="/WEB-INF/jsp/", suffix=".jsp", viewname="test" ->
 * "/WEB-INF/jsp/test.jsp"
 *
 * <p>As a special feature, redirect URLs can be specified via the "redirect:"
 * prefix. E.g.: "redirect:myAction.do" will trigger a redirect to the given
 * URL, rather than resolution as standard view name. This is typically used
 * for redirecting to a controller URL after finishing a form workflow.
 *
 * <p>Furthermore, forward URLs can be specified via the "forward:" prefix. E.g.:
 * "forward:myAction.do" will trigger a forward to the given URL, rather than
 * resolution as standard view name. This is typically used for controller URLs;
 * it is not supposed to be used for JSP URLs - use logical view names there.
 *
 * <p>Note: This class does not support localized resolution, i.e. resolving
 * a symbolic view name to different resources depending on the current locale.
 *
 * <p>Note: When chaining ViewResolvers, a UrlBasedViewResolver always needs
 * to be last, as it will attempt to resolve any view name, no matter whether
 * the underlying resource actually exists.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @since 13.12.2003
 * @see #setViewClass
 * @see #setPrefix
 * @see #setSuffix
 * @see #setRequestContextAttribute
 * @see #REDIRECT_URL_PREFIX
 * @see AbstractUrlBasedView
 * @see InternalResourceView
 * @see org.springframework.web.servlet.view.velocity.VelocityView
 * @see org.springframework.web.servlet.view.freemarker.FreeMarkerView
 */
public class UrlBasedViewResolver extends AbstractCachingViewResolver implements Ordered {

	/**
	 * Prefix for special view names that specify a redirect URL (usually
	 * to a controller after a form has been submitted and processed).
	 * Such view names will not be resolved in the configured default
	 * way but rather be treated as special shortcut.
	 */
	public static final String REDIRECT_URL_PREFIX = "redirect:";

	/**
	 * Prefix for special view names that specify a forward URL (usually
	 * to a controller after a form has been submitted and processed).
	 * Such view names will not be resolved in the configured default
	 * way but rather be treated as special shortcut.
	 */
	public static final String FORWARD_URL_PREFIX = "forward:";


	private Class viewClass;

	private String prefix = "";

	private String suffix = "";

	private String[] viewNames = null;

	private String contentType;

	private boolean redirectContextRelative = true;

	private boolean redirectHttp10Compatible = true;

	private String requestContextAttribute;

	private int order = Integer.MAX_VALUE;

	/** Map of static attributes, keyed by attribute name (String) */
	private final Map	staticAttributes = new HashMap();


	/**
	 * Set the view class that should be used to create views.
	 * @param viewClass class that is assignable to the required view class
	 * (by default, AbstractUrlBasedView)
	 * @see AbstractUrlBasedView
	 */
	public void setViewClass(Class viewClass) {
		if (viewClass == null || !requiredViewClass().isAssignableFrom(viewClass)) {
			throw new IllegalArgumentException(
					"Given view class [" + (viewClass != null ? viewClass.getName() : null) +
					"] is not of type [" + requiredViewClass().getName() + "]");
		}
		this.viewClass = viewClass;
	}

	/**
	 * Return the view class to be used to create views.
	 */
	protected Class getViewClass() {
		return this.viewClass;
	}

	/**
	 * Return the required type of view for this resolver.
	 * This implementation returns AbstractUrlBasedView.
	 * @see AbstractUrlBasedView
	 */
	protected Class requiredViewClass() {
		return AbstractUrlBasedView.class;
	}

	/**
	 * Set the prefix that gets prepended to view names when building a URL.
	 */
	public void setPrefix(String prefix) {
		this.prefix = (prefix != null ? prefix : "");
	}

	/**
	 * Return the prefix that gets prepended to view names when building a URL.
	 */
	protected String getPrefix() {
		return this.prefix;
	}

	/**
	 * Set the suffix that gets appended to view names when building a URL.
	 */
	public void setSuffix(String suffix) {
		this.suffix = (suffix != null ? suffix : "");
	}

	/**
	 * Return the suffix that gets appended to view names when building a URL.
	 */
	protected String getSuffix() {
		return this.suffix;
	}

	/**
	 * Set the content type for all views.
	 * <p>May be ignored by view classes if the view itself is assumed
	 * to set the content type, e.g. in case of JSPs.
	 */
	public void setContentType(String contentType) {
		this.contentType = contentType;
	}

	/**
	 * Return the content type for all views, if any.
	 */
	protected String getContentType() {
		return this.contentType;
	}

	/**
	 * Set whether to interpret a given redirect URL that starts with a
	 * slash ("/") as relative to the current ServletContext, i.e. as
	 * relative to the web application root.
	 * <p>Default is "true": A redirect URL that starts with a slash will be
	 * interpreted as relative to the web application root, i.e. the context
	 * path will be prepended to the URL.
	 * <p><b>Redirect URLs can be specified via the "redirect:" prefix.</b>
	 * E.g.: "redirect:myAction.do"
	 * @see RedirectView#setContextRelative
	 * @see #REDIRECT_URL_PREFIX
	 */
	public void setRedirectContextRelative(boolean redirectContextRelative) {
		this.redirectContextRelative = redirectContextRelative;
	}

	/**
	 * Return whether to interpret a given redirect URL that starts with a
	 * slash ("/") as relative to the current ServletContext, i.e. as
	 * relative to the web application root.
	 */
	protected boolean isRedirectContextRelative() {
		return this.redirectContextRelative;
	}

	/**
	 * Set whether redirects should stay compatible with HTTP 1.0 clients.