org.springframework/spring-web/5.1.5.RELEASE : org/springframework/http/CacheControl.java

CacheControl
https://github.com/spring-projects/spring-framework: Spring Web (Spring IO)
Apache License, Version 2.0
Juergen Hoeller
/*
 * Copyright 2002-2018 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.http;

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 CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS) will result in Cache-Control: "max-age=3600"
Preventing cache with CacheControl cc = CacheControl.noStore() will result in Cache-Control: "no-store"
Advanced cases like CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS).noTransform().cachePublic() will result in 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, Juergen Hoeller
See Also: rfc7234 section 5.2.2

 * HTTP caching - Google developers reference
Mark Nottingham's cache documentation
Since: 4.2/**
 * A builder for creating "Cache-Control" HTTP response headers.
 *
 * <p>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.
 *
 * <ul>
 * <li>Caching HTTP responses with {@code CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS)}
 * will result in {@code Cache-Control: "max-age=3600"}</li>
 * <li>Preventing cache with {@code CacheControl cc = CacheControl.noStore()}
 * will result in {@code Cache-Control: "no-store"}</li>
 * <li>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"}</li>
 * </ul>
 *
 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2">rfc7234 section 5.2.2</a>
 * @see <a href="https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching">
 * HTTP caching - Google developers reference</a>
 * @see <a href="https://www.mnot.net/cache_docs/">Mark Nottingham's cache documentation</a>
 */
public class CacheControl {

	private long maxAge = -1;

	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;

	private long staleWhileRevalidate = -1;

	private long staleIfError = -1;

	private long sMaxAge = -1;


	Create an empty CacheControl instance.
See Also: empty()/**
	 * 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".
Returns: this, to facilitate method chaining/**
	 * Return an empty directive.
	 * <p>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 (cachePrivate()) or transformed (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 (mustRevalidate() 
Params: maxAge – the maximum time the response should be cached
unit – the time unit of the maxAge argument
See Also: rfc7234 section 5.2.2.8
Returns: this, to facilitate method chaining/**
	 * Add a "max-age=" directive.
	 * <p>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.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.8">rfc7234 section 5.2.2.8</a>
	 */
	public static CacheControl maxAge(long maxAge, TimeUnit unit) {
		CacheControl cc = new CacheControl();
		cc.maxAge = unit.toSeconds(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 noStore() directive should be used instead of #noCache(). 
See Also: rfc7234 section 5.2.2.2
Returns: this, to facilitate method chaining/**
	 * Add a "no-cache" directive.
	 * <p>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.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.2">rfc7234 section 5.2.2.2</a>
	 */
	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.
See Also: rfc7234 section 5.2.2.3
Returns: this, to facilitate method chaining/**
	 * Add a "no-store" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.3">rfc7234 section 5.2.2.3</a>
	 */
	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.
See Also: rfc7234 section 5.2.2.1
Returns: this, to facilitate method chaining/**
	 * Add a "must-revalidate" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.1">rfc7234 section 5.2.2.1</a>
	 */
	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.
See Also: rfc7234 section 5.2.2.4
Returns: this, to facilitate method chaining/**
	 * Add a "no-transform" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.4">rfc7234 section 5.2.2.4</a>
	 */
	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.
See Also: rfc7234 section 5.2.2.5
Returns: this, to facilitate method chaining/**
	 * Add a "public" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.5">rfc7234 section 5.2.2.5</a>
	 */
	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.
See Also: rfc7234 section 5.2.2.6
Returns: this, to facilitate method chaining/**
	 * Add a "private" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.6">rfc7234 section 5.2.2.6</a>
	 */
	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).
See Also: rfc7234 section 5.2.2.7
Returns: this, to facilitate method chaining/**
	 * Add a "proxy-revalidate" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.7">rfc7234 section 5.2.2.7</a>
	 */
	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.
Params: sMaxAge – the maximum time the response should be cached
unit – the time unit of the sMaxAge argument
See Also: rfc7234 section 5.2.2.9
Returns: this, to facilitate method chaining/**
	 * Add an "s-maxage" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc7234#section-5.2.2.9">rfc7234 section 5.2.2.9</a>
	 */
	public CacheControl sMaxAge(long sMaxAge, TimeUnit unit) {
		this.sMaxAge = unit.toSeconds(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).
Params: staleWhileRevalidate – the maximum time the response should be used while being revalidated
unit – the time unit of the staleWhileRevalidate argument
See Also: rfc5861 section 3
Returns: this, to facilitate method chaining/**
	 * Add a "stale-while-revalidate" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc5861#section-3">rfc5861 section 3</a>
	 */
	public CacheControl staleWhileRevalidate(long staleWhileRevalidate, TimeUnit unit) {
		this.staleWhileRevalidate = unit.toSeconds(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.
Params: staleIfError – the maximum time the response should be used when errors are encountered
unit – the time unit of the staleIfError argument
See Also: rfc5861 section 4
Returns: this, to facilitate method chaining/**
	 * Add a "stale-if-error" directive.
	 * <p>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 <a href="https://tools.ietf.org/html/rfc5861#section-4">rfc5861 section 4</a>
	 */
	public CacheControl staleIfError(long staleIfError, TimeUnit unit) {
		this.staleIfError = unit.toSeconds(staleIfError);
		return this;
	}


	Return the "Cache-Control" header value, if any.
Returns: the header value, or null if no directive was added/**
	 * 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.
Returns: the header value (potentially empty)/**
	 * Return the "Cache-Control" header value.
	 * @return the header value (potentially empty)
	 */
	private String toHeaderValue() {
		StringBuilder headerValue = new StringBuilder();
		if (this.maxAge != -1) {
			appendDirective(headerValue, "max-age=" + this.maxAge);
		}
		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 != -1) {
			appendDirective(headerValue, "s-maxage=" + this.sMaxAge);
		}
		if (this.staleIfError != -1) {
			appendDirective(headerValue, "stale-if-error=" + this.staleIfError);
		}
		if (this.staleWhileRevalidate != -1) {
			appendDirective(headerValue, "stale-while-revalidate=" + this.staleWhileRevalidate);
		}
		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() + "]";
	}

}
Author:	Brian Clozel, Juergen Hoeller
See Also:	rfc7234 section 5.2.2 * HTTP caching - Google developers reference Mark Nottingham's cache documentation
Since:	4.2
Params:	maxAge – the maximum time the response should be cached unit – the time unit of the `maxAge` argument
See Also:	rfc7234 section 5.2.2.8
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.2
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.3
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.1
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.4
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.5
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.6
Returns:	`this`, to facilitate method chaining
See Also:	rfc7234 section 5.2.2.7
Returns:	`this`, to facilitate method chaining
Params:	sMaxAge – the maximum time the response should be cached unit – the time unit of the `sMaxAge` argument
See Also:	rfc7234 section 5.2.2.9
Returns:	`this`, to facilitate method chaining
Params:	staleWhileRevalidate – the maximum time the response should be used while being revalidated unit – the time unit of the `staleWhileRevalidate` argument
See Also:	rfc5861 section 3
Returns:	`this`, to facilitate method chaining
Params:	staleIfError – the maximum time the response should be used when errors are encountered unit – the time unit of the `staleIfError` argument
See Also:	rfc5861 section 4
Returns:	`this`, to facilitate method chaining
/

org.springframework/ spring-web/ 5.1.5.RELEASE/ org/springframework/http/CacheControl.java
