org.springframework.http

Class CacheControl

java.lang.Object

org.springframework.http.CacheControl

public class CacheControl
extends java.lang.Object

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.

Since:

4.2

Author:

Brian Clozel, Juergen Hoeller

See Also:

rfc7234 section 5.2.2, HTTP caching - Google developers reference, Mark Nottingham's cache documentation

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	cachePrivate
private boolean	cachePublic
private long	maxAge
private boolean	mustRevalidate
private boolean	noCache
private boolean	noStore
private boolean	noTransform
private boolean	proxyRevalidate
private long	sMaxAge
private long	staleIfError
private long	staleWhileRevalidate

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	CacheControl() Create an empty CacheControl instance.

Method Summary

Modifier and Type	Method and Description
private void	appendDirective(java.lang.StringBuilder builder, java.lang.String value)
CacheControl	cachePrivate() Add a "private" directive.
CacheControl	cachePublic() Add a "public" directive.
static CacheControl	empty() Return an empty directive.
java.lang.String	getHeaderValue() Return the "Cache-Control" header value, if any.
static CacheControl	maxAge(long maxAge, java.util.concurrent.TimeUnit unit) Add a "max-age=" directive.
CacheControl	mustRevalidate() Add a "must-revalidate" directive.
static CacheControl	noCache() Add a "no-cache" directive.
static CacheControl	noStore() Add a "no-store" directive.
CacheControl	noTransform() Add a "no-transform" directive.
CacheControl	proxyRevalidate() Add a "proxy-revalidate" directive.
CacheControl	sMaxAge(long sMaxAge, java.util.concurrent.TimeUnit unit) Add an "s-maxage" directive.
CacheControl	staleIfError(long staleIfError, java.util.concurrent.TimeUnit unit) Add a "stale-if-error" directive.
CacheControl	staleWhileRevalidate(long staleWhileRevalidate, java.util.concurrent.TimeUnit unit) Add a "stale-while-revalidate" directive.
private java.lang.String	toHeaderValue() Return the "Cache-Control" header value.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

maxAge

private long maxAge

noCache

private boolean noCache

noStore

private boolean noStore

mustRevalidate

private boolean mustRevalidate

noTransform

private boolean noTransform

cachePublic

private boolean cachePublic

cachePrivate

private boolean cachePrivate

proxyRevalidate

private boolean proxyRevalidate

staleWhileRevalidate

private long staleWhileRevalidate

staleIfError

private long staleIfError

sMaxAge

private long sMaxAge

Constructor Detail

CacheControl

protected CacheControl()

Create an empty CacheControl instance.

See Also:

empty()

Method Detail

empty

public static CacheControl empty()

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

maxAge

public static CacheControl maxAge(long maxAge,
                                  java.util.concurrent.TimeUnit unit)

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()

Parameters:

maxAge - the maximum time the response should be cached

unit - the time unit of the maxAge argument

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.8

noCache

public static CacheControl noCache()

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().

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.2

noStore

public static CacheControl noStore()

Add a "no-store" directive.

This directive is well suited for preventing caches (browsers and proxies) to cache the content of responses.

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.3

mustRevalidate

public CacheControl mustRevalidate()

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.

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.1

noTransform

public CacheControl noTransform()

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.

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.4

cachePublic

public CacheControl cachePublic()

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.

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.5

cachePrivate

public CacheControl cachePrivate()

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.

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.6

proxyRevalidate

public CacheControl proxyRevalidate()

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).

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.7

sMaxAge

public CacheControl sMaxAge(long sMaxAge,
                            java.util.concurrent.TimeUnit unit)

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.

Parameters:

sMaxAge - the maximum time the response should be cached

unit - the time unit of the sMaxAge argument

Returns:

this, to facilitate method chaining

See Also:

rfc7234 section 5.2.2.9

staleWhileRevalidate

public CacheControl staleWhileRevalidate(long staleWhileRevalidate,
                                         java.util.concurrent.TimeUnit unit)

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).

Parameters:

staleWhileRevalidate - the maximum time the response should be used while being revalidated

unit - the time unit of the staleWhileRevalidate argument

Returns:

this, to facilitate method chaining

See Also:

rfc5861 section 3

staleIfError

public CacheControl staleIfError(long staleIfError,
                                 java.util.concurrent.TimeUnit unit)

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.

Parameters:

staleIfError - the maximum time the response should be used when errors are encountered

unit - the time unit of the staleIfError argument

Returns:

this, to facilitate method chaining

See Also:

rfc5861 section 4

getHeaderValue

@Nullable
public java.lang.String getHeaderValue()

Return the "Cache-Control" header value, if any.

Returns:

the header value, or null if no directive was added

toHeaderValue

private java.lang.String toHeaderValue()

Return the "Cache-Control" header value.

Returns:

the header value (potentially empty)

appendDirective

private void appendDirective(java.lang.StringBuilder builder,
                             java.lang.String value)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object