/*
 * Copyright 2002-2017 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 org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;

Convenient subclass of UrlBasedViewResolver that supports InternalResourceView (i.e. Servlets and JSPs) and subclasses such as JstlView. 
The view class for all views generated by this resolver can be specified via UrlBasedViewResolver.setViewClass. See UrlBasedViewResolver's javadoc for details. The default is InternalResourceView, or JstlView if the JSTL API is present. 
BTW, it's good practice to put JSP files that just serve as views under
WEB-INF, to hide them from direct access (e.g. via a manually entered URL).
Only controllers will be able to access them then.
Note: When chaining ViewResolvers, an InternalResourceViewResolver
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
See Also:
UrlBasedViewResolver.setViewClass
UrlBasedViewResolver.setPrefix
UrlBasedViewResolver.setSuffix
UrlBasedViewResolver.setRequestContextAttribute
InternalResourceView
JstlView
Since:
17.02.2003/**
 * Convenient subclass of {@link UrlBasedViewResolver} that supports
 * {@link InternalResourceView} (i.e. Servlets and JSPs) and subclasses
 * such as {@link JstlView}.
 *
 * <p>The view class for all views generated by this resolver can be specified
 * via {@link #setViewClass}. See {@link UrlBasedViewResolver}'s javadoc for details.
 * The default is {@link InternalResourceView}, or {@link JstlView} if the
 * JSTL API is present.
 *
 * <p>BTW, it's good practice to put JSP files that just serve as views under
 * WEB-INF, to hide them from direct access (e.g. via a manually entered URL).
 * Only controllers will be able to access them then.
 *
 * <p><b>Note:</b> When chaining ViewResolvers, an InternalResourceViewResolver
 * 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
 * @since 17.02.2003
 * @see #setViewClass
 * @see #setPrefix
 * @see #setSuffix
 * @see #setRequestContextAttribute
 * @see InternalResourceView
 * @see JstlView
 */
public class InternalResourceViewResolver extends UrlBasedViewResolver {

	private static final boolean jstlPresent = ClassUtils.isPresent(
			"javax.servlet.jsp.jstl.core.Config", InternalResourceViewResolver.class.getClassLoader());

	@Nullable
	private Boolean alwaysInclude;


	
Sets the default view class to requiredViewClass: by default InternalResourceView, or JstlView if the JSTL API is present. /**
	 * Sets the default {@link #setViewClass view class} to {@link #requiredViewClass}:
	 * by default {@link InternalResourceView}, or {@link JstlView} if the JSTL API
	 * is present.
	 */
	public InternalResourceViewResolver() {
		Class<?> viewClass = requiredViewClass();
		if (InternalResourceView.class == viewClass && jstlPresent) {
			viewClass = JstlView.class;
		}
		setViewClass(viewClass);
	}

	
A convenience constructor that allows for specifying prefix and suffix as constructor arguments. 
Params:
prefix – the prefix that gets prepended to view names when building a URL
suffix – the suffix that gets appended to view names when building a URL
Since:
4.3/**
	 * A convenience constructor that allows for specifying {@link #setPrefix prefix}
	 * and {@link #setSuffix suffix} as constructor arguments.
	 * @param prefix the prefix that gets prepended to view names when building a URL
	 * @param suffix the suffix that gets appended to view names when building a URL
	 * @since 4.3
	 */
	public InternalResourceViewResolver(String prefix, String suffix) {
		this();
		setPrefix(prefix);
		setSuffix(suffix);
	}


	
This resolver requires InternalResourceView. /**
	 * This resolver requires {@link InternalResourceView}.
	 */
	@Override
	protected Class<?> requiredViewClass() {
		return InternalResourceView.class;
	}

	
Specify whether to always include the view rather than forward to it.
Default is "false". Switch this flag on to enforce the use of a
Servlet include, even if a forward would be possible.
See Also:
setAlwaysInclude.setAlwaysInclude/**
	 * Specify whether to always include the view rather than forward to it.
	 * <p>Default is "false". Switch this flag on to enforce the use of a
	 * Servlet include, even if a forward would be possible.
	 * @see InternalResourceView#setAlwaysInclude
	 */
	public void setAlwaysInclude(boolean alwaysInclude) {
		this.alwaysInclude = alwaysInclude;
	}


	@Override
	protected AbstractUrlBasedView buildView(String viewName) throws Exception {
		InternalResourceView view = (InternalResourceView) super.buildView(viewName);
		if (this.alwaysInclude != null) {
			view.setAlwaysInclude(this.alwaysInclude);
		}
		view.setPreventDispatchLoop(true);
		return view;
	}

}