org.springframework.web.servlet.view.InternalResourceView Maven / Gradle / Ivy
/*
* 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
*
* https://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.Map;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
import org.springframework.web.util.WebUtils;
/**
* Wrapper for a JSP or other resource within the same web application.
* Exposes model objects as request attributes and forwards the request to
* the specified resource URL using a {@link javax.servlet.RequestDispatcher}.
*
* A URL for this view is supposed to specify a resource within the web
* application, suitable for RequestDispatcher's {@code forward} or
* {@code include} method.
*
*
If operating within an already included request or within a response that
* has already been committed, this view will fall back to an include instead of
* a forward. This can be enforced by calling {@code response.flushBuffer()}
* (which will commit the response) before rendering the view.
*
*
Typical usage with {@link InternalResourceViewResolver} looks as follows,
* from the perspective of the DispatcherServlet context definition:
*
*
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
* <property name="prefix" value="/WEB-INF/jsp/"/>
* <property name="suffix" value=".jsp"/>
* </bean>
*
* Every view name returned from a handler will be translated to a JSP
* resource (for example: "myView" -> "/WEB-INF/jsp/myView.jsp"), using
* this view class by default.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Rob Harrop
* @see javax.servlet.RequestDispatcher#forward
* @see javax.servlet.RequestDispatcher#include
* @see javax.servlet.ServletResponse#flushBuffer
* @see InternalResourceViewResolver
* @see JstlView
*/
public class InternalResourceView extends AbstractUrlBasedView {
private boolean alwaysInclude = false;
private boolean preventDispatchLoop = false;
/**
* Constructor for use as a bean.
* @see #setUrl
* @see #setAlwaysInclude
*/
public InternalResourceView() {
}
/**
* Create a new InternalResourceView with the given URL.
* @param url the URL to forward to
* @see #setAlwaysInclude
*/
public InternalResourceView(String url) {
super(url);
}
/**
* Create a new InternalResourceView with the given URL.
* @param url the URL to forward to
* @param alwaysInclude whether to always include the view rather than forward to it
*/
public InternalResourceView(String url, boolean alwaysInclude) {
super(url);
this.alwaysInclude = alwaysInclude;
}
/**
* 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 javax.servlet.RequestDispatcher#forward
* @see javax.servlet.RequestDispatcher#include
* @see #useInclude(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
*/
public void setAlwaysInclude(boolean alwaysInclude) {
this.alwaysInclude = alwaysInclude;
}
/**
* Set whether to explicitly prevent dispatching back to the
* current handler path.
*
Default is "false". Switch this to "true" for convention-based
* views where a dispatch back to the current handler path is a
* definitive error.
*/
public void setPreventDispatchLoop(boolean preventDispatchLoop) {
this.preventDispatchLoop = preventDispatchLoop;
}
/**
* An ApplicationContext is not strictly required for InternalResourceView.
*/
@Override
protected boolean isContextRequired() {
return false;
}
/**
* Render the internal resource given the specified model.
* This includes setting the model as request attributes.
*/
@Override
protected void renderMergedOutputModel(
Map model, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Expose the model object as request attributes.
exposeModelAsRequestAttributes(model, request);
// Expose helpers as request attributes, if any.
exposeHelpers(request);
// Determine the path for the request dispatcher.
String dispatcherPath = prepareForRendering(request, response);
// Obtain a RequestDispatcher for the target resource (typically a JSP).
RequestDispatcher rd = getRequestDispatcher(request, dispatcherPath);
if (rd == null) {
throw new ServletException("Could not get RequestDispatcher for [" + getUrl() +
"]: Check that the corresponding file exists within your web application archive!");
}
// If already included or response already committed, perform include, else forward.
if (useInclude(request, response)) {
response.setContentType(getContentType());
if (logger.isDebugEnabled()) {
logger.debug("Including [" + getUrl() + "]");
}
rd.include(request, response);
}
else {
// Note: The forwarded resource is supposed to determine the content type itself.
if (logger.isDebugEnabled()) {
logger.debug("Forwarding to [" + getUrl() + "]");
}
rd.forward(request, response);
}
}
/**
* Expose helpers unique to each rendering operation. This is necessary so that
* different rendering operations can't overwrite each other's contexts etc.
* Called by {@link #renderMergedOutputModel(Map, HttpServletRequest, HttpServletResponse)}.
* The default implementation is empty. This method can be overridden to add
* custom helpers as request attributes.
* @param request current HTTP request
* @throws Exception if there's a fatal error while we're adding attributes
* @see #renderMergedOutputModel
* @see JstlView#exposeHelpers
*/
protected void exposeHelpers(HttpServletRequest request) throws Exception {
}
/**
* Prepare for rendering, and determine the request dispatcher path
* to forward to (or to include).
*
This implementation simply returns the configured URL.
* Subclasses can override this to determine a resource to render,
* typically interpreting the URL in a different manner.
* @param request current HTTP request
* @param response current HTTP response
* @return the request dispatcher path to use
* @throws Exception if preparations failed
* @see #getUrl()
*/
protected String prepareForRendering(HttpServletRequest request, HttpServletResponse response)
throws Exception {
String path = getUrl();
Assert.state(path != null, "'url' not set");
if (this.preventDispatchLoop) {
String uri = request.getRequestURI();
if (path.startsWith("/") ? uri.equals(path) : uri.equals(StringUtils.applyRelativePath(uri, path))) {
throw new ServletException("Circular view path [" + path + "]: would dispatch back " +
"to the current handler URL [" + uri + "] again. Check your ViewResolver setup! " +
"(Hint: This may be the result of an unspecified view, due to default view name generation.)");
}
}
return path;
}
/**
* Obtain the RequestDispatcher to use for the forward/include.
*
The default implementation simply calls
* {@link HttpServletRequest#getRequestDispatcher(String)}.
* Can be overridden in subclasses.
* @param request current HTTP request
* @param path the target URL (as returned from {@link #prepareForRendering})
* @return a corresponding RequestDispatcher
*/
@Nullable
protected RequestDispatcher getRequestDispatcher(HttpServletRequest request, String path) {
return request.getRequestDispatcher(path);
}
/**
* Determine whether to use RequestDispatcher's {@code include} or
* {@code forward} method.
*
Performs a check whether an include URI attribute is found in the request,
* indicating an include request, and whether the response has already been committed.
* In both cases, an include will be performed, as a forward is not possible anymore.
* @param request current HTTP request
* @param response current HTTP response
* @return {@code true} for include, {@code false} for forward
* @see javax.servlet.RequestDispatcher#forward
* @see javax.servlet.RequestDispatcher#include
* @see javax.servlet.ServletResponse#isCommitted
* @see org.springframework.web.util.WebUtils#isIncludeRequest
*/
protected boolean useInclude(HttpServletRequest request, HttpServletResponse response) {
return (this.alwaysInclude || WebUtils.isIncludeRequest(request) || response.isCommitted());
}
}