This commit adds AssertJ compatible assertions for HTTP request and
responses, including headers, media type, and response body. The latter
delegate to the recently included JSON assert support.
See gh-21178
Historically, we have rarely intentionally thrown a
NullPointerException in the Spring Framework. Instead, we prefer to
throw either an IllegalArgumentException or IllegalStateException
instead of a NullPointerException.
However, changes to the code in recent times have introduced the use of
Objects.requireNonNull(Object) which throws a NullPointerException
without an explicit error message.
The latter ends up providing less context than a NullPointerException
thrown by the JVM (since Java 14) due to actually de-referencing a
null-pointer. See https://openjdk.org/jeps/358.
In light of that, this commit revises our current use of
Objects.requireNonNull(Object) by removing it or replacing it with
Assert.notNull().
However, we still use Objects.requireNonNull(T, String) in a few places
where we are required to throw a NullPointerException in order to
comply with a third-party contract such as Reactive Streams.
Closes gh-32430
Prior to this commit, gh-21783 introduced `ReadOnlyHttpHeaders` to avoid
parsing media types multiple times during the lifetime of an HTTP
exchange: such values are cached and the headers map is made read-only.
This also added a new `HttpHeaders.writableHttpHeaders` method to unwrap
the read-only variant when needed.
It turns out this method sends the wrong signal to the community
because:
* the underlying map might be unmodifiable even if this is not an
instance of ReadOnlyHttpHeaders
* developers were assuming that modifying the collection that backs the
read-only instance would work around the cached values for
Content-Type and Accept headers
This commit adds more documentation to highlight the desired behavior
for cached values by the read-only variant, and deprecates the
`writableHttpHeaders` method as `ReadOnlyHttpHeaders` is package private
and we should not surface that concept anyway.
Instead, this commit unwraps the read-only variant if needed when a new
HttpHeaders instance is created.
Closes gh-32116
This commit ensures pathExtension predicate is skipped when the value
is null, in order to provide a more predictable behavior, and allow
a better compatibility with collections not supporting null elements
like the ones created by List#of.
Closes gh-32404
