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Improve conditional requests support

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Prior to this commit, Spring MVC and Spring WebFlux would not support
conditional requests with `If-Match` preconditions. As underlined in the
RFC9110 Section 13.1, those are related to the `If-None-Match`
conditions, but this time only performing requests if the resource
matches the given ETag.

This feature, and in general the `"*"` request Etag, are generally
useful to prevent "lost updates" when performing a POST/PUT request: we
want to ensure that we're updating a version with a known version or
create a new resource only if it doesn't exist already.

This commit adds `If-Match` conditional requests support and ensures
that both `If-Match` and `If-None-Match` work well with `"*"` request
ETags.

We can't rely on `checkNotModified(null)`, as the compiler can't decide
between method variants accepting an ETag `String` or a Last Modified
`long`. Instead, developers should use empty ETags `""` to signal that
no resource is known on the server side.

Closes gh-24881
This commit is contained in:
Brian Clozel
2022-06-21 19:18:33 +02:00
parent a3d3667e64
commit 0783f0762d
7 changed files with 877 additions and 763 deletions
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10
spring-webflux/src/main/java/org/springframework/web/reactive/function/server/ServerRequest.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2020 the original author or authors.
* Copyright 2002-2022 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.
@@ -352,13 +352,14 @@ public interface ServerRequest {
* also with conditional POST/PUT/DELETE requests.
* <p><strong>Note:</strong> you can use either
* this {@link #checkNotModified(Instant)} method; or
* {@code #checkNotModified(String)}. If you want enforce both
* {@code #checkNotModified(String)}. If you want to enforce both
* a strong entity tag and a Last-Modified value,
* as recommended by the HTTP specification,
* then you should use {@link #checkNotModified(Instant, String)}.
* @param etag the entity tag that the application determined
* for the underlying resource. This parameter will be padded
* with quotes (") if necessary.
* with quotes (") if necessary. Use an empty string {@code ""}
* for no value.
* @return a corresponding response if the request qualifies as not
* modified, or an empty result otherwise
* @since 5.2.5
@@ -391,7 +392,8 @@ public interface ServerRequest {
* application determined for the underlying resource
* @param etag the entity tag that the application determined
* for the underlying resource. This parameter will be padded
* with quotes (") if necessary.
* with quotes (") if necessary. Use an empty string {@code ""}
* for no value.
* @return a corresponding response if the request qualifies as not
* modified, or an empty result otherwise.
* @since 5.2.5