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/*
* Copyright 2002-2019 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.http;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;
/**
* A builder for creating "Cache-Control" HTTP response headers.
*
* Adding Cache-Control directives to HTTP responses can significantly improve the client
* experience when interacting with a web application. This builder creates opinionated
* "Cache-Control" headers with response directives only, with several use cases in mind.
*
*
* - Caching HTTP responses with {@code CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS)}
* will result in {@code Cache-Control: "max-age=3600"}
* - Preventing cache with {@code CacheControl cc = CacheControl.noStore()}
* will result in {@code Cache-Control: "no-store"}
* - Advanced cases like {@code CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS).noTransform().cachePublic()}
* will result in {@code Cache-Control: "max-age=3600, no-transform, public"}
*
*
* Note that to be efficient, Cache-Control headers should be written along HTTP validators
* such as "Last-Modified" or "ETag" headers.
*
* @author Brian Clozel
* @author Juergen Hoeller
* @since 4.2
* @see rfc7234 section 5.2.2
* @see
* HTTP caching - Google developers reference
* @see Mark Nottingham's cache documentation
*/
public class CacheControl {
@Nullable
private Duration maxAge;
private boolean noCache = false;
private boolean noStore = false;
private boolean mustRevalidate = false;
private boolean noTransform = false;
private boolean cachePublic = false;
private boolean cachePrivate = false;
private boolean proxyRevalidate = false;
@Nullable
private Duration staleWhileRevalidate;
@Nullable
private Duration staleIfError;
@Nullable
private Duration sMaxAge;
/**
* Create an empty CacheControl instance.
* @see #empty()
*/
protected CacheControl() {
}
/**
* Return an empty directive.
*
This is well suited for using other optional directives without "max-age",
* "no-cache" or "no-store".
* @return {@code this}, to facilitate method chaining
*/
public static CacheControl empty() {
return new CacheControl();
}
/**
* Add a "max-age=" directive.
*
This directive is well suited for publicly caching resources, knowing that
* they won't change within the configured amount of time. Additional directives
* can be also used, in case resources shouldn't be cached ({@link #cachePrivate()})
* or transformed ({@link #noTransform()}) by shared caches.
*
In order to prevent caches to reuse the cached response even when it has
* become stale (i.e. the "max-age" delay is passed), the "must-revalidate"
* directive should be set ({@link #mustRevalidate()}
* @param maxAge the maximum time the response should be cached
* @param unit the time unit of the {@code maxAge} argument
* @return {@code this}, to facilitate method chaining
* @see #maxAge(Duration)
* @see rfc7234 section 5.2.2.8
*/
public static CacheControl maxAge(long maxAge, TimeUnit unit) {
return maxAge(Duration.ofSeconds(unit.toSeconds(maxAge)));
}
/**
* Add a "max-age=" directive.
*
This directive is well suited for publicly caching resources, knowing that
* they won't change within the configured amount of time. Additional directives
* can be also used, in case resources shouldn't be cached ({@link #cachePrivate()})
* or transformed ({@link #noTransform()}) by shared caches.
*
In order to prevent caches to reuse the cached response even when it has
* become stale (i.e. the "max-age" delay is passed), the "must-revalidate"
* directive should be set ({@link #mustRevalidate()}
* @param maxAge the maximum time the response should be cached
* @return {@code this}, to facilitate method chaining
* @since 5.2
* @see rfc7234 section 5.2.2.8
*/
public static CacheControl maxAge(Duration maxAge) {
CacheControl cc = new CacheControl();
cc.maxAge = maxAge;
return cc;
}
/**
* Add a "no-cache" directive.
*
This directive is well suited for telling caches that the response
* can be reused only if the client revalidates it with the server.
* This directive won't disable cache altogether and may result with clients
* sending conditional requests (with "ETag", "If-Modified-Since" headers)
* and the server responding with "304 - Not Modified" status.
*
In order to disable caching and minimize requests/responses exchanges,
* the {@link #noStore()} directive should be used instead of {@code #noCache()}.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.2
*/
public static CacheControl noCache() {
CacheControl cc = new CacheControl();
cc.noCache = true;
return cc;
}
/**
* Add a "no-store" directive.
*
This directive is well suited for preventing caches (browsers and proxies)
* to cache the content of responses.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.3
*/
public static CacheControl noStore() {
CacheControl cc = new CacheControl();
cc.noStore = true;
return cc;
}
/**
* Add a "must-revalidate" directive.
*
This directive indicates that once it has become stale, a cache MUST NOT
* use the response to satisfy subsequent requests without successful validation
* on the origin server.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.1
*/
public CacheControl mustRevalidate() {
this.mustRevalidate = true;
return this;
}
/**
* Add a "no-transform" directive.
*
This directive indicates that intermediaries (caches and others) should
* not transform the response content. This can be useful to force caches and
* CDNs not to automatically gzip or optimize the response content.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.4
*/
public CacheControl noTransform() {
this.noTransform = true;
return this;
}
/**
* Add a "public" directive.
*
This directive indicates that any cache MAY store the response,
* even if the response would normally be non-cacheable or cacheable
* only within a private cache.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.5
*/
public CacheControl cachePublic() {
this.cachePublic = true;
return this;
}
/**
* Add a "private" directive.
*
This directive indicates that the response message is intended
* for a single user and MUST NOT be stored by a shared cache.
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.6
*/
public CacheControl cachePrivate() {
this.cachePrivate = true;
return this;
}
/**
* Add a "proxy-revalidate" directive.
*
This directive has the same meaning as the "must-revalidate" directive,
* except that it does not apply to private caches (i.e. browsers, HTTP clients).
* @return {@code this}, to facilitate method chaining
* @see rfc7234 section 5.2.2.7
*/
public CacheControl proxyRevalidate() {
this.proxyRevalidate = true;
return this;
}
/**
* Add an "s-maxage" directive.
*
This directive indicates that, in shared caches, the maximum age specified
* by this directive overrides the maximum age specified by other directives.
* @param sMaxAge the maximum time the response should be cached
* @param unit the time unit of the {@code sMaxAge} argument
* @return {@code this}, to facilitate method chaining
* @see #sMaxAge(Duration)
* @see rfc7234 section 5.2.2.9
*/
public CacheControl sMaxAge(long sMaxAge, TimeUnit unit) {
return sMaxAge(Duration.ofSeconds(unit.toSeconds(sMaxAge)));
}
/**
* Add an "s-maxage" directive.
*
This directive indicates that, in shared caches, the maximum age specified
* by this directive overrides the maximum age specified by other directives.
* @param sMaxAge the maximum time the response should be cached
* @return {@code this}, to facilitate method chaining
* @since 5.2
* @see rfc7234 section 5.2.2.9
*/
public CacheControl sMaxAge(Duration sMaxAge) {
this.sMaxAge = sMaxAge;
return this;
}
/**
* Add a "stale-while-revalidate" directive.
*
This directive indicates that caches MAY serve the response in which it
* appears after it becomes stale, up to the indicated number of seconds.
* If a cached response is served stale due to the presence of this extension,
* the cache SHOULD attempt to revalidate it while still serving stale responses
* (i.e. without blocking).
* @param staleWhileRevalidate the maximum time the response should be used while being revalidated
* @param unit the time unit of the {@code staleWhileRevalidate} argument
* @return {@code this}, to facilitate method chaining
* @see #staleWhileRevalidate(Duration)
* @see rfc5861 section 3
*/
public CacheControl staleWhileRevalidate(long staleWhileRevalidate, TimeUnit unit) {
return staleWhileRevalidate(Duration.ofSeconds(unit.toSeconds(staleWhileRevalidate)));
}
/**
* Add a "stale-while-revalidate" directive.
*
This directive indicates that caches MAY serve the response in which it
* appears after it becomes stale, up to the indicated number of seconds.
* If a cached response is served stale due to the presence of this extension,
* the cache SHOULD attempt to revalidate it while still serving stale responses
* (i.e. without blocking).
* @param staleWhileRevalidate the maximum time the response should be used while being revalidated
* @return {@code this}, to facilitate method chaining
* @since 5.2
* @see rfc5861 section 3
*/
public CacheControl staleWhileRevalidate(Duration staleWhileRevalidate) {
this.staleWhileRevalidate = staleWhileRevalidate;
return this;
}
/**
* Add a "stale-if-error" directive.
*
This directive indicates that when an error is encountered, a cached stale response
* MAY be used to satisfy the request, regardless of other freshness information.
* @param staleIfError the maximum time the response should be used when errors are encountered
* @param unit the time unit of the {@code staleIfError} argument
* @return {@code this}, to facilitate method chaining
* @see #staleIfError(Duration)
* @see rfc5861 section 4
*/
public CacheControl staleIfError(long staleIfError, TimeUnit unit) {
return staleIfError(Duration.ofSeconds(unit.toSeconds(staleIfError)));
}
/**
* Add a "stale-if-error" directive.
*
This directive indicates that when an error is encountered, a cached stale response
* MAY be used to satisfy the request, regardless of other freshness information.
* @param staleIfError the maximum time the response should be used when errors are encountered
* @return {@code this}, to facilitate method chaining
* @since 5.2
* @see rfc5861 section 4
*/
public CacheControl staleIfError(Duration staleIfError) {
this.staleIfError = staleIfError;
return this;
}
/**
* Return the "Cache-Control" header value, if any.
* @return the header value, or {@code null} if no directive was added
*/
@Nullable
public String getHeaderValue() {
String headerValue = toHeaderValue();
return (StringUtils.hasText(headerValue) ? headerValue : null);
}
/**
* Return the "Cache-Control" header value.
* @return the header value (potentially empty)
*/
private String toHeaderValue() {
StringBuilder headerValue = new StringBuilder();
if (this.maxAge != null) {
appendDirective(headerValue, "max-age=" + this.maxAge.getSeconds());
}
if (this.noCache) {
appendDirective(headerValue, "no-cache");
}
if (this.noStore) {
appendDirective(headerValue, "no-store");
}
if (this.mustRevalidate) {
appendDirective(headerValue, "must-revalidate");
}
if (this.noTransform) {
appendDirective(headerValue, "no-transform");
}
if (this.cachePublic) {
appendDirective(headerValue, "public");
}
if (this.cachePrivate) {
appendDirective(headerValue, "private");
}
if (this.proxyRevalidate) {
appendDirective(headerValue, "proxy-revalidate");
}
if (this.sMaxAge != null) {
appendDirective(headerValue, "s-maxage=" + this.sMaxAge.getSeconds());
}
if (this.staleIfError != null) {
appendDirective(headerValue, "stale-if-error=" + this.staleIfError.getSeconds());
}
if (this.staleWhileRevalidate != null) {
appendDirective(headerValue, "stale-while-revalidate=" + this.staleWhileRevalidate.getSeconds());
}
return headerValue.toString();
}
private void appendDirective(StringBuilder builder, String value) {
if (builder.length() > 0) {
builder.append(", ");
}
builder.append(value);
}
@Override
public String toString() {
return "CacheControl [" + toHeaderValue() + "]";
}
}