Background
Spring 3.1 introduced the @ComponentScan annotation, which can accept
an optional array of include and/or exclude @Filter annotations, e.g.
@ComponentScan(
basePackages = "com.acme.app",
includeFilters = { @Filter(MyStereotype.class), ... }
)
@Configuration
public class AppConfig { ... }
@ComponentScan and other annotations related to @Configuration class
processing such as @Import, @ImportResource and the @Enable*
annotations are parsed using reflection in certain code paths, e.g.
when registered directly against AnnotationConfigApplicationContext,
and via ASM in other code paths, e.g. when a @Configuration class is
discovered via an XML bean definition or when included via the
@Import annotation.
The ASM-based approach is designed to avoid premature classloading of
user types and is instrumental in providing tooling support (STS, etc).
Prior to this commit, the ASM-based routines for reading annotation
attributes were unable to recurse into nested annotations, such as in
the @Filter example above. Prior to Spring 3.1 this was not a problem,
because prior to @ComponentScan, there were no cases of nested
annotations in the framework.
This limitation manifested itself in cases where users encounter
the ASM-based annotation parsing code paths AND declare
@ComponentScan annotations with explicit nested @Filter annotations.
In these cases, the 'includeFilters' and 'excludeFilters' attributes
are simply empty where they should be populated, causing the framework
to ignore the filter directives and provide incorrect results from
component scanning.
The purpose of this change then, is to introduce the capability on the
ASM side to recurse into nested annotations and annotation arrays. The
challenge in doing so is that the nested annotations themselves cannot
be realized as annotation instances, so must be represented as a
nested Map (or, as described below, the new AnnotationAttributes type).
Furthermore, the reflection-based annotation parsing must also be
updated to treat nested annotations in a similar fashion; even though
the reflection-based approach has no problem accessing nested
annotations (it just works out of the box), for substitutability
against the AnnotationMetadata SPI, both ASM- and reflection-based
implementations should return the same results in any case. Therefore,
the reflection-based StandardAnnotationMetadata has also been updated
with an optional 'nestedAnnotationsAsMap' constructor argument that is
false by default to preserve compatibility in the rare case that
StandardAnnotationMetadata is being used outside the core framework.
Within the framework, all uses of StandardAnnotationMetadata have been
updated to set this new flag to true, meaning that nested annotation
results will be consistent regardless the parsing approach used.
Spr9031Tests corners this bug and demonstrates that nested @Filter
annotations can be parsed and read in both the ASM- and
reflection-based paths.
Major changes
- AnnotationAttributes has been introduced as a concrete
LinkedHashMap<String, Object> to be used anywhere annotation
attributes are accessed, providing error reporting on attribute
lookup and convenient type-safe access to common annotation types
such as String, String[], boolean, int, and nested annotation and
annotation arrays, with the latter two also returned as
AnnotationAttributes instances.
- AnnotationUtils#getAnnotationAttributes methods now return
AnnotationAttributes instances, even though for binary compatibility
the signatures of these methods have been preserved as returning
Map<String, Object>.
- AnnotationAttributes#forMap provides a convenient mechanism for
adapting any Map<String, Object> into an AnnotationAttributes
instance. In the case that the Map is already actually of
type AnnotationAttributes, it is simply casted and returned.
Otherwise, the map is supplied to the AnnotationAttributes(Map)
constructor and wrapped in common collections style.
- The protected MetadataUtils#attributesFor(Metadata, Class) provides
further convenience in the many locations throughout the
.context.annotation packagage that depend on annotation attribute
introspection.
- ASM-based core.type.classreading package reworked
Specifically, AnnotationAttributesReadingVisitor has been enhanced to
support recursive reading of annotations and annotation arrays, for
example in @ComponentScan's nested array of @Filter annotations,
ensuring that nested AnnotationAttributes objects are populated as
described above.
AnnotationAttributesReadingVisitor has also been refactored for
clarity, being broken up into several additional ASM
AnnotationVisitor implementations. Given that all types are
package-private here, these changes represent no risk to binary
compatibility.
- Reflection-based StandardAnnotationMetadata updated
As described above, the 'nestedAnnotationsAsMap' constructor argument
has been added, and all framework-internal uses of this class have
been updated to set this flag to true.
Issue: SPR-7979, SPR-8719, SPR-9031
Prior to this change, roughly 5% (~300 out of 6000+) of files under the
source tree had CRLF line endings as opposed to the majority which have
LF endings.
This change normalizes these files to LF for consistency going forward.
Command used:
$ git ls-files | xargs file | grep CRLF | cut -d":" -f1 | xargs dos2unix
Issue: SPR-5608
Prior to this change, an assumption was made in
AbstractAutowireCapableBeanFactory that any factory-method would have
zero parameters. This may not be the case in @Bean methods.
We now look for the factory-method by name in a more flexible fashion
that accomodates the possibility of method parameters.
There remains at least one edge cases here where things could still fail,
for example a @Configuration class could have two FactoryBean-returning
methods of the same name, but each with different generic FactoryBean
types and different parameter lists. In this case, the implementation
may infer and return the wrong object type, as it currently returns
the first match for the given factory-method name. The complexity cost
of ensuring that this never happens is not likely worth the trouble
given the very low likelihood of such an arrangement.
Issue: SPR-8762
Properties such as 'spring.profiles.active' cannot be specified at the
command line under Bash and other shells due to variable naming
constraints. This change allows for exchanging underscores for periods
as well as capitalizing property names for more idiomatic naming when
dealing with environment variables.
For example, Spring will respect equally either of the following:
spring.profiles.active=p1 java -classpath ... MyApp
SPRING_PROFILES_ACTIVE=p1 java -classpath ... MyApp
The former is not possible under Bash, while the latter is. No code or
configuration changes are required; SystemEnvironmentPropertySource
adapts for these varations automatically.
SystemEnvironmentPropertySource is added by default as
"systemEnvironment" to StandardEnvironment and all subtypes, taking the
place of the plain MapPropertySource that was in use before this change.
Issue: SPR-8869
Currently the combine method consolidates "/*" and "/hotel"
into "/hotel". However if the first pattern contains URI template
variables, the consolidation seems wrong. The fix is to prevent
the consolidation if the first pattern contains "{".
Add BridgeMethodResolver#isJava6VisibilityBridgeMethodPair to
distinguish between (a) bridge methods introduced in Java 6 to
compensate for inheriting public methods from non-public superclasses
and (b) bridge methods that have existed since Java 5 to accommodate
return type covariance and generic parameters.
In the former case, annotations should be looked up from the original
bridged method (SPR-7900). In the latter, the annotation should be
looked up against the bridge method itself (SPR-8660).
As noted in the Javadoc for the new method, see
http://stas-blogspot.blogspot.com/2010/03/java-bridge-methods-explained.html
for a useful description of the various types of bridge methods, as
well as http://bugs.sun.com/view_bug.do?bug_id=6342411, the bug fixed in
Java 6 resulting in the introduction of 'visibility bridge methods'.
Issue: SPR-8660, SPR-7900
Remove all convenience variants of #findAllAnnotationAttributes and
refactor the remaining method to accept a MetadataReaderFactory
instead of creating its own SimpleMetadataReaderFactory internally.
This allows clients to use non-default class loaders as well as
customize the particular MetadataReaderFactory to be used (e.g.
'simple' vs 'caching', etc).
Issue: SPR-8752
Provides a convenient mechanism for activating an additional profile
while preserving those that are already active, as opposed to
calling #setActiveProfiles with the contents of #getActiveProfiles plus
the new profile.
Issue: SPR-8548
Chris Beams
Juergen Hoeller
Sam Brannen
Rossen Stoyanchev
Arjen Poutsma