/*
* 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.support;
import java.util.HashSet;
import java.util.Set;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.HttpRequestMethodNotSupportedException;
import org.springframework.web.HttpSessionRequiredException;
import org.springframework.web.context.support.WebApplicationObjectSupport;
/**
* Convenient superclass for any kind of web content generator,
* like {@link org.springframework.web.servlet.mvc.AbstractController}
* and {@link org.springframework.web.servlet.mvc.WebContentInterceptor}.
* Can also be used for custom handlers that have their own
* {@link org.springframework.web.servlet.HandlerAdapter}.
*
* <p>Supports HTTP cache control options. The usage of corresponding
* HTTP headers can be controlled via the "useExpiresHeader" and
* "useCacheControlHeader" properties.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see #setCacheSeconds
* @see #setRequireSession
*/
public abstract class WebContentGenerator extends WebApplicationObjectSupport {
/** HTTP method "HEAD" */
public static final String METHOD_HEAD = "HEAD";
/** HTTP method "GET" */
public static final String METHOD_GET = "GET";
/** HTTP method "POST" */
public static final String METHOD_POST = "POST";
private static final String HEADER_PRAGMA = "Pragma";
private static final String HEADER_EXPIRES = "Expires";
private static final String HEADER_CACHE_CONTROL = "Cache-Control";
/** Set of supported methods. HEAD, GET and POST by default. */
private Set supportedMethods = new HashSet();
private boolean requireSession = false;
/** Use HTTP 1.0 expires header? */
private boolean useExpiresHeader = true;
/** Use HTTP 1.1 cache-control header? */
private boolean useCacheControlHeader = true;
private int cacheSeconds = -1;
public WebContentGenerator() {
this.supportedMethods.add(METHOD_HEAD);
this.supportedMethods.add(METHOD_GET);
this.supportedMethods.add(METHOD_POST);
}
/**
* Set the HTTP methods that this content generator should support.
* Default is HEAD, GET and POST.
*/
public final void setSupportedMethods(String[] methods) {
if (ObjectUtils.isEmpty(methods)) {
throw new IllegalArgumentException("'supportedMethods' must not be empty");
}
this.supportedMethods.clear();
for (int i = 0; i < methods.length; i++) {
this.supportedMethods.add(methods[i]);
}
}
/**
* Return the HTTP methods that this content generator supports.
*/
public final String[] getSupportedMethods() {
return StringUtils.toStringArray(this.supportedMethods);
}
/**
* Set whether a session should be required to handle requests.
*/
public final void setRequireSession(boolean requireSession) {
this.requireSession = requireSession;
}
/**
* Return whether a session is required to handle requests.
*/
public final boolean isRequireSession() {
return this.requireSession;
}
/**
* Set whether to use the HTTP 1.0 expires header. Default is "true".
* <p>Note: Cache headers will only get applied if caching is enabled
* (or explicitly prevented) for the current request.
*/
public final void setUseExpiresHeader(boolean useExpiresHeader) {
this.useExpiresHeader = useExpiresHeader;
}
/**
* Return whether the HTTP 1.0 expires header is used.
*/
public final boolean isUseExpiresHeader() {
return this.useExpiresHeader;
}
/**
* Set whether to use the HTTP 1.1 cache-control header. Default is "true".
* <p>Note: Cache headers will only get applied if caching is enabled
* (or explicitly prevented) for the current request.
*/
public final void setUseCacheControlHeader(boolean useCacheControlHeader) {
this.useCacheControlHeader = useCacheControlHeader;
}
/**
* Return whether the HTTP 1.1 cache-control header is used.
*/
public final boolean isUseCacheControlHeader() {
return this.useCacheControlHeader;
}
/**
* Cache content for the given number of seconds. Default is -1,
* indicating no generation of cache-related headers.
* <p>Only if this is set to 0 (no cache) or a positive value (cache for
* this many seconds) will this class generate cache headers.
* <p>The headers can be overwritten by subclasses, before content is generated.
*/
public final void setCacheSeconds(int seconds) {
this.cacheSeconds = seconds;
}
/**
* Return the number of seconds that content is cached.
*/
public final int getCacheSeconds() {
return this.cacheSeconds;
}
/**
* Check and prepare the given request and response according to the settings
* of this generator. Checks for supported methods and a required session,
* and applies the number of cache seconds specified for this generator.
* @param request current HTTP request
* @param response current HTTP response
* @param lastModified if the mapped handler provides Last-Modified support
* @throws ServletException if the request cannot be handled because a check failed
*/
protected final void checkAndPrepare(
HttpServletRequest request, HttpServletResponse response, boolean lastModified)
throws ServletException {
checkAndPrepare(request, response, this.cacheSeconds, lastModified);
}
/**
* Check and prepare the given request and response according to the settings
* of this generator. Checks for supported methods and a required session,
* and applies the given number of cache seconds.
* @param request current HTTP request
* @param response current HTTP response
* @param cacheSeconds positive number of seconds into the future that the
* response should be cacheable for, 0 to prevent caching
* @param lastModified if the mapped handler provides Last-Modified support
* @throws ServletException if the request cannot be handled because a check failed
*/
protected final void checkAndPrepare(
HttpServletRequest request, HttpServletResponse response, int cacheSeconds, boolean lastModified)
throws ServletException {
// Check whether we should support the request method.
String method = request.getMethod();
if (!this.supportedMethods.contains(method)) {
throw new HttpRequestMethodNotSupportedException(method);
}
// Check whether a session is required.
if (this.requireSession) {
if (request.getSession(false) == null) {
throw new HttpSessionRequiredException("Pre-existing session required but none found");
}
}
// Do declarative cache control.
// Revalidate if the controller supports last-modified.
applyCacheSeconds(response, cacheSeconds, lastModified);
}
/**
* Prevent the response from being cached.
* See <code>http://www.mnot.net/cache_docs</code>.
*/
protected final void preventCaching(HttpServletResponse response) {
response.setHeader(HEADER_PRAGMA, "No-cache");
if (this.useExpiresHeader) {
// HTTP 1.0 header
response.setDateHeader(HEADER_EXPIRES, 1L);
}
if (this.useCacheControlHeader) {
// HTTP 1.1 header: "no-cache" is the standard value,
// "no-store" is necessary to prevent caching on FireFox.
response.setHeader(HEADER_CACHE_CONTROL, "no-cache");
response.addHeader(HEADER_CACHE_CONTROL, "no-store");
}
}
/**
* Set HTTP headers to allow caching for the given number of seconds.
* Does not tell the browser to revalidate the resource.
* @param response current HTTP response
* @param seconds number of seconds into the future that the response
* should be cacheable for
* @see #cacheForSeconds(javax.servlet.http.HttpServletResponse, int, boolean)
*/
protected final void cacheForSeconds(HttpServletResponse response, int seconds) {
cacheForSeconds(response, seconds, false);
}
/**
* Set HTTP headers to allow caching for the given number of seconds.
* Tells the browser to revalidate the resource if mustRevalidate is
* <code>true</code>.
* @param response the current HTTP response
* @param seconds number of seconds into the future that the response
* should be cacheable for
* @param mustRevalidate whether the client should revalidate the resource
* (typically only necessary for controllers with last-modified support)
*/
protected final void cacheForSeconds(HttpServletResponse response, int seconds, boolean mustRevalidate) {
if (this.useExpiresHeader) {
// HTTP 1.0 header
response.setDateHeader(HEADER_EXPIRES, System.currentTimeMillis() + seconds * 1000L);
}
if (this.useCacheControlHeader) {
// HTTP 1.1 header
String headerValue = "max-age=" + seconds;
if (mustRevalidate) {
headerValue += ", must-revalidate";
}
response.setHeader(HEADER_CACHE_CONTROL, headerValue);
}
}
/**
* Apply the given cache seconds and generate corresponding HTTP headers,
* i.e. allow caching for the given number of seconds in case of a positive
* value, prevent caching if given a 0 value, do nothing else.
* Does not tell the browser to revalidate the resource.
* @param response current HTTP response
* @param seconds positive number of seconds into the future that the
* response should be cacheable for, 0 to prevent caching
* @see #cacheForSeconds(javax.servlet.http.HttpServletResponse, int, boolean)
*/
protected final void applyCacheSeconds(HttpServletResponse response, int seconds) {
applyCacheSeconds(response, seconds, false);
}
/**
* Apply the given cache seconds and generate respective HTTP headers.
* <p>That is, allow caching for the given number of seconds in the
* case of a positive value, prevent caching if given a 0 value, else
* do nothing (i.e. leave caching to the client).
* @param response the current HTTP response
* @param seconds the (positive) number of seconds into the future that
* the response should be cacheable for; 0 to prevent caching; and
* a negative value to leave caching to the client.
* @param mustRevalidate whether the client should revalidate the resource
* (typically only necessary for controllers with last-modified support)
*/
protected final void applyCacheSeconds(HttpServletResponse response, int seconds, boolean mustRevalidate) {
if (seconds > 0) {
cacheForSeconds(response, seconds, mustRevalidate);
}
else if (seconds == 0) {
preventCaching(response);
}
// Leave caching to the client otherwise.
}
}
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