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
Prior to this commit, gh-31609 added the current observation context as
a request attribute for `WebClient` calls. While it was not confirmed as
the main cause, this feature was linked to several reports of memory
leaks. This would indeed attach more memory to the request object graph
at runtime - although it shouldn't prevent its collection by the GC.
This commit removes this feature and instead developers should get the
current observation from the reactor context if they wish to interact
with it.
Closes gh-32198
This commit introduce a change of behaviour when component scan is used
with conditions. Previously, any condition in the REGISTER_BEAN phase
were ignored and the scan was applied regardless of the outcome of
those conditions. This is because REGISTER_BEAN condition evaluation
happens later in the bean factory preparation.
Rather than ignoring those conditions, this commit fails fast when it
detects such use case. Code will have to be adapted accordingly.
Closes gh-23206
