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Improve HTTP caching flexiblity

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This commit improves HTTP caching defaults and flexibility in
Spring MVC.

1) Better default caching headers

The `WebContentGenerator` abstract class has been updated with
better HTTP defaults for HTTP caching, in line with current
browsers and proxies implementation (wide support of HTTP1.1, etc);
depending on the `setCacheSeconds` value:

* sends "Cache-Control: max-age=xxx" for caching responses and
do not send a "must-revalidate" value by default.
* sends "Cache-Control: no-store" or "Cache-Control: no-cache"
in order to prevent caching

Other methods used to set specific header such as
`setUseExpiresHeader` or `setAlwaysMustRevalidate` are now deprecated
in favor of `setCacheControl` for better flexibility.
Using one of the deprecated methods re-enables previous HTTP caching
behavior.

This change is applied in many Handlers, since
`WebContentGenerator` is extended by `AbstractController`,
`WebContentInterceptor`, `ResourceHttpRequestHandler` and others.

2) New CacheControl builder class

This new class brings more flexibility and allows developers
to set custom HTTP caching headers.

Several strategies are provided:

* `CacheControl.maxAge(int)` for caching responses with a
"Cache-Control: max-age=xxx" header
* `CacheControl.noStore()` prevents responses from being cached
with a "Cache-Control: no-store" header
* `CacheControl.noCache()` forces caches to revalidate the cached
response before reusing it, with a "Cache-Control: no-store" header.

From that point, it is possible to chain method calls to craft a
custom CacheControl instance:

```
CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS)
    .cachePublic().noTransform();
```

3) Configuring HTTP caching in Resource Handlers

On top of the existing ways of configuring caching mechanisms,
it is now possible to use a custom `CacheControl` to serve
resources:

```
@Configuration
public class MyWebConfig extends WebMvcConfigurerAdapter {

  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    CacheControl cc = CacheControl.maxAge(1, TimeUnit.HOURS);
    registry.addResourceHandler("/resources/**)
            .addResourceLocations("classpath:/resources/")
            .setCacheControl(cc);
  }
}
```

or

```
<mvc:resources mapping="/resources/**" location="classpath:/resources/">
  <mvc:cachecontrol max-age="3600" cache-public="true"/>
</mvc:resources>
```

Issue: SPR-2779, SPR-6834, SPR-7129, SPR-9543, SPR-10464
This commit is contained in:
Brian Clozel
2015-03-11 11:19:52 +01:00
parent 953608ec49
commit 38f32e3816
21 changed files with 818 additions and 192 deletions
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294
spring-web/src/main/java/org/springframework/http/CacheControl.java Normal file
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/*
* Copyright 2002-2015 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.util.StringUtils;
/**
* 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-Modifed" or "ETag" headers.
*
* @author Brian Clozel
* @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>
* @since 4.2
*/
public class CacheControl {
private boolean mustRevalidate;
private boolean noCache;
private boolean noStore;
private boolean noTransform;
private boolean cachePublic;
private boolean cachePrivate;
private boolean proxyRevalidate;
private long maxAge;
private long sMaxAge;
/**
* Create a CacheControl instance with default values,
* i.e. that will produce an empty "Cache-Control" header value.
*/
protected CacheControl() {
this.mustRevalidate = false;
this.noCache = false;
this.noStore = false;
this.noTransform = false;
this.cachePublic = false;
this.cachePrivate = false;
this.proxyRevalidate = false;
this.maxAge = -1;
this.sMaxAge = -1;
}
/**
* 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-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 "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.
*
* @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;
}
/**
* Return an empty directive.
*
* <p>This is well suited for using other optional directives without "no-cache", "no-store" or "max-age".
*
* @return {@code this}, to facilitate method chaining
*/
public static CacheControl empty() {
CacheControl cc = new CacheControl();
return cc;
}
/**
* 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
*
* <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
*
* <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
*
* <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
*
* <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 a "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;
}
/**
* Return the "Cache-Control" header value
*
* @return null if no directive was added, the header value otherwise
*/
public String getHeaderValue() {
StringBuilder ccValue = new StringBuilder();
if (this.maxAge != -1) {
appendDirective(ccValue, "max-age=" + Long.toString(maxAge));
}
if (this.noCache) {
appendDirective(ccValue, "no-cache");
}
if (this.noStore) {
appendDirective(ccValue, "no-store");
}
if (this.mustRevalidate) {
appendDirective(ccValue, "must-revalidate");
}
if (this.noTransform) {
appendDirective(ccValue, "no-transform");
}
if (this.cachePublic) {
appendDirective(ccValue, "public");
}
if (this.cachePrivate) {
appendDirective(ccValue, "private");
}
if (this.proxyRevalidate) {
appendDirective(ccValue, "proxy-revalidate");
}
if (this.sMaxAge != -1) {
appendDirective(ccValue, "s-maxage=" + Long.toString(this.sMaxAge));
}
String ccHeaderValue = ccValue.toString();
if (StringUtils.hasText(ccHeaderValue)) {
return ccHeaderValue;
}
return null;
}
private void appendDirective(StringBuilder b, String value) {
if (b.length() > 0) {
b.append(", ");
}
b.append(value);
}
}