org.springframework.core.annotation.MergedAnnotations Maven / Gradle / Ivy
/*
* Copyright 2002-2019 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
*
* https://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.core.annotation;
import java.lang.annotation.Annotation;
import java.lang.annotation.Inherited;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.function.Predicate;
import java.util.stream.Stream;
import org.springframework.lang.Nullable;
/**
* Provides access to a collection of merged annotations, usually obtained
* from a source such as a {@link Class} or {@link Method}.
*
* Each merged annotation represents a view where the attribute values may be
* "merged" from different source values, typically:
*
*
* - Explicit and Implicit {@link AliasFor @AliasFor} declarations on one or
* more attributes within the annotation
* - Explicit {@link AliasFor @AliasFor} declarations for a meta-annotation
* - Convention based attribute aliases for a meta-annotation
* - From a meta-annotation declaration
*
*
* For example, a {@code @PostMapping} annotation might be defined as follows:
*
*
* @Retention(RetentionPolicy.RUNTIME)
* @RequestMapping(method = RequestMethod.POST)
* public @interface PostMapping {
*
* @AliasFor(attribute = "path")
* String[] value() default {};
*
* @AliasFor(attribute = "value")
* String[] path() default {};
* }
*
*
* If a method is annotated with {@code @PostMapping("/home")} it will contain
* merged annotations for both {@code @PostMapping} and the meta-annotation
* {@code @RequestMapping}. The merged view of the {@code @RequestMapping}
* annotation will contain the following attributes:
*
*
*
* Name
* Value
* Source
*
*
* value
* "/home"
* Declared in {@code @PostMapping}
*
*
* path
* "/home"
* Explicit {@code @AliasFor}
*
*
* method
* RequestMethod.POST
* Declared in meta-annotation
*
*
*
* {@link MergedAnnotations} can be obtained {@linkplain #from(AnnotatedElement)
* from} any Java {@link AnnotatedElement}. They may also be used for sources that
* don't use reflection (such as those that directly parse bytecode).
*
*
Different {@linkplain SearchStrategy search strategies} can be used to locate
* related source elements that contain the annotations to be aggregated. For
* example, {@link SearchStrategy#TYPE_HIERARCHY} will search both superclasses and
* implemented interfaces.
*
*
From a {@link MergedAnnotations} instance you can either
* {@linkplain #get(String) get} a single annotation, or {@linkplain #stream()
* stream all annotations} or just those that match {@linkplain #stream(String)
* a specific type}. You can also quickly tell if an annotation
* {@linkplain #isPresent(String) is present}.
*
*
Here are some typical examples:
*
*
* // is an annotation present or meta-present?
* mergedAnnotations.isPresent(ExampleAnnotation.class);
*
* // get the merged "value" attribute of ExampleAnnotation (either directly or
* // meta-present)
* mergedAnnotations.get(ExampleAnnotation.class).getString("value");
*
* // get all meta-annotations but no directly present annotations
* mergedAnnotations.stream().filter(MergedAnnotation::isMetaPresent);
*
* // get all ExampleAnnotation declarations (including any meta-annotations) and
* // print the merged "value" attributes
* mergedAnnotations.stream(ExampleAnnotation.class)
* .map(mergedAnnotation -> mergedAnnotation.getString("value"))
* .forEach(System.out::println);
*
*
* @author Phillip Webb
* @author Sam Brannen
* @since 5.2
* @see MergedAnnotation
* @see MergedAnnotationCollectors
* @see MergedAnnotationPredicates
* @see MergedAnnotationSelectors
*/
public interface MergedAnnotations extends Iterable> {
/**
* Determine if the specified annotation is either directly present or
* meta-present.
* Equivalent to calling {@code get(annotationType).isPresent()}.
* @param annotationType the annotation type to check
* @return {@code true} if the annotation is present
*/
boolean isPresent(Class annotationType);
/**
* Determine if the specified annotation is either directly present or
* meta-present.
* Equivalent to calling {@code get(annotationType).isPresent()}.
* @param annotationType the fully qualified class name of the annotation type
* to check
* @return {@code true} if the annotation is present
*/
boolean isPresent(String annotationType);
/**
* Determine if the specified annotation is directly present.
*
Equivalent to calling {@code get(annotationType).isDirectlyPresent()}.
* @param annotationType the annotation type to check
* @return {@code true} if the annotation is directly present
*/
boolean isDirectlyPresent(Class annotationType);
/**
* Determine if the specified annotation is directly present.
* Equivalent to calling {@code get(annotationType).isDirectlyPresent()}.
* @param annotationType the fully qualified class name of the annotation type
* to check
* @return {@code true} if the annotation is directly present
*/
boolean isDirectlyPresent(String annotationType);
/**
* Get the {@linkplain MergedAnnotationSelectors#nearest() nearest} matching
* annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the annotation type to get
* @return a {@link MergedAnnotation} instance
*/
MergedAnnotation get(Class annotationType);
/**
* Get the {@linkplain MergedAnnotationSelectors#nearest() nearest} matching
* annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the annotation type to get
* @param predicate a predicate that must match, or {@code null} if only
* type matching is required
* @return a {@link MergedAnnotation} instance
* @see MergedAnnotationPredicates
*/
MergedAnnotation get(Class annotationType,
@Nullable Predicate> predicate);
/**
* Get a matching annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the annotation type to get
* @param predicate a predicate that must match, or {@code null} if only
* type matching is required
* @param selector a selector used to choose the most appropriate annotation
* within an aggregate, or {@code null} to select the
* {@linkplain MergedAnnotationSelectors#nearest() nearest}
* @return a {@link MergedAnnotation} instance
* @see MergedAnnotationPredicates
* @see MergedAnnotationSelectors
*/
MergedAnnotation get(Class annotationType,
@Nullable Predicate> predicate,
@Nullable MergedAnnotationSelector selector);
/**
* Get the {@linkplain MergedAnnotationSelectors#nearest() nearest} matching
* annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the fully qualified class name of the annotation type
* to get
* @return a {@link MergedAnnotation} instance
*/
MergedAnnotation get(String annotationType);
/**
* Get the {@linkplain MergedAnnotationSelectors#nearest() nearest} matching
* annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the fully qualified class name of the annotation type
* to get
* @param predicate a predicate that must match, or {@code null} if only
* type matching is required
* @return a {@link MergedAnnotation} instance
* @see MergedAnnotationPredicates
*/
MergedAnnotation get(String annotationType,
@Nullable Predicate> predicate);
/**
* Get a matching annotation or meta-annotation of the specified type, or
* {@link MergedAnnotation#missing()} if none is present.
* @param annotationType the fully qualified class name of the annotation type
* to get
* @param predicate a predicate that must match, or {@code null} if only
* type matching is required
* @param selector a selector used to choose the most appropriate annotation
* within an aggregate, or {@code null} to select the
* {@linkplain MergedAnnotationSelectors#nearest() nearest}
* @return a {@link MergedAnnotation} instance
* @see MergedAnnotationPredicates
* @see MergedAnnotationSelectors
*/
MergedAnnotation get(String annotationType,
@Nullable Predicate> predicate,
@Nullable MergedAnnotationSelector selector);
/**
* Stream all annotations and meta-annotations that match the specified
* type. The resulting stream follows the same ordering rules as
* {@link #stream()}.
* @param annotationType the annotation type to match
* @return a stream of matching annotations
*/
Stream> stream(Class annotationType);
/**
* Stream all annotations and meta-annotations that match the specified
* type. The resulting stream follows the same ordering rules as
* {@link #stream()}.
* @param annotationType the fully qualified class name of the annotation type
* to match
* @return a stream of matching annotations
*/
Stream> stream(String annotationType);
/**
* Stream all annotations and meta-annotations contained in this collection.
* The resulting stream is ordered first by the
* {@linkplain MergedAnnotation#getAggregateIndex() aggregate index} and then
* by the annotation distance (with the closest annotations first). This ordering
* means that, for most use-cases, the most suitable annotations appear
* earliest in the stream.
* @return a stream of annotations
*/
Stream> stream();
/**
* Create a new {@link MergedAnnotations} instance containing all
* annotations and meta-annotations from the specified element. The
* resulting instance will not include any inherited annotations. If you
* want to include those as well you should use
* {@link #from(AnnotatedElement, SearchStrategy)} with an appropriate
* {@link SearchStrategy}.
* @param element the source element
* @return a {@link MergedAnnotations} instance containing the element's
* annotations
*/
static MergedAnnotations from(AnnotatedElement element) {
return from(element, SearchStrategy.DIRECT);
}
/**
* Create a new {@link MergedAnnotations} instance containing all
* annotations and meta-annotations from the specified element and,
* depending on the {@link SearchStrategy}, related inherited elements.
* @param element the source element
* @param searchStrategy the search strategy to use
* @return a {@link MergedAnnotations} instance containing the merged
* element annotations
*/
static MergedAnnotations from(AnnotatedElement element, SearchStrategy searchStrategy) {
return from(element, searchStrategy, RepeatableContainers.standardRepeatables());
}
/**
* Create a new {@link MergedAnnotations} instance containing all
* annotations and meta-annotations from the specified element and,
* depending on the {@link SearchStrategy}, related inherited elements.
* @param element the source element
* @param searchStrategy the search strategy to use
* @param repeatableContainers the repeatable containers that may be used by
* the element annotations or the meta-annotations
* @return a {@link MergedAnnotations} instance containing the merged
* element annotations
*/
static MergedAnnotations from(AnnotatedElement element, SearchStrategy searchStrategy,
RepeatableContainers repeatableContainers) {
return TypeMappedAnnotations.from(element, searchStrategy, repeatableContainers, AnnotationFilter.PLAIN);
}
/**
* Create a new {@link MergedAnnotations} instance containing all
* annotations and meta-annotations from the specified element and,
* depending on the {@link SearchStrategy}, related inherited elements.
* @param element the source element
* @param searchStrategy the search strategy to use
* @param repeatableContainers the repeatable containers that may be used by
* the element annotations or the meta-annotations
* @param annotationFilter an annotation filter used to restrict the
* annotations considered
* @return a {@link MergedAnnotations} instance containing the merged
* element annotations
*/
static MergedAnnotations from(AnnotatedElement element, SearchStrategy searchStrategy,
RepeatableContainers repeatableContainers, AnnotationFilter annotationFilter) {
return TypeMappedAnnotations.from(element, searchStrategy, repeatableContainers, annotationFilter);
}
/**
* Create a new {@link MergedAnnotations} instance from the specified
* annotations.
* @param annotations the annotations to include
* @return a {@link MergedAnnotations} instance containing the annotations
* @see #from(Object, Annotation...)
*/
static MergedAnnotations from(Annotation... annotations) {
return from(annotations, annotations);
}
/**
* Create a new {@link MergedAnnotations} instance from the specified
* annotations.
* @param source the source for the annotations. This source is used only
* for information and logging. It does not need to actually
* contain the specified annotations, and it will not be searched.
* @param annotations the annotations to include
* @return a {@link MergedAnnotations} instance containing the annotations
* @see #from(Annotation...)
* @see #from(AnnotatedElement)
*/
static MergedAnnotations from(Object source, Annotation... annotations) {
return from(source, annotations, RepeatableContainers.standardRepeatables());
}
/**
* Create a new {@link MergedAnnotations} instance from the specified
* annotations.
* @param source the source for the annotations. This source is used only
* for information and logging. It does not need to actually
* contain the specified annotations, and it will not be searched.
* @param annotations the annotations to include
* @param repeatableContainers the repeatable containers that may be used by
* meta-annotations
* @return a {@link MergedAnnotations} instance containing the annotations
*/
static MergedAnnotations from(Object source, Annotation[] annotations, RepeatableContainers repeatableContainers) {
return TypeMappedAnnotations.from(source, annotations, repeatableContainers, AnnotationFilter.PLAIN);
}
/**
* Create a new {@link MergedAnnotations} instance from the specified
* annotations.
* @param source the source for the annotations. This source is used only
* for information and logging. It does not need to actually
* contain the specified annotations, and it will not be searched.
* @param annotations the annotations to include
* @param repeatableContainers the repeatable containers that may be used by
* meta-annotations
* @param annotationFilter an annotation filter used to restrict the
* annotations considered
* @return a {@link MergedAnnotations} instance containing the annotations
*/
static MergedAnnotations from(Object source, Annotation[] annotations,
RepeatableContainers repeatableContainers, AnnotationFilter annotationFilter) {
return TypeMappedAnnotations.from(source, annotations, repeatableContainers, annotationFilter);
}
/**
* Create a new {@link MergedAnnotations} instance from the specified
* collection of directly present annotations. This method allows a
* {@link MergedAnnotations} instance to be created from annotations that
* are not necessarily loaded using reflection. The provided annotations
* must all be {@link MergedAnnotation#isDirectlyPresent() directly present}
* and must have a {@link MergedAnnotation#getAggregateIndex() aggregate
* index} of {@code 0}.
*
* The resulting {@link MergedAnnotations} instance will contain both the
* specified annotations, and any meta-annotations that can be read using
* reflection.
* @param annotations the annotations to include
* @return a {@link MergedAnnotations} instance containing the annotations
* @see MergedAnnotation#of(ClassLoader, Object, Class, java.util.Map)
*/
static MergedAnnotations of(Collection> annotations) {
return MergedAnnotationsCollection.of(annotations);
}
/**
* Search strategies supported by
* {@link MergedAnnotations#from(AnnotatedElement, SearchStrategy)}.
*
* Each strategy creates a different set of aggregates that will be
* combined to create the final {@link MergedAnnotations}.
*/
enum SearchStrategy {
/**
* Find only directly declared annotations, without considering
* {@link Inherited @Inherited} annotations and without searching
* superclasses or implemented interfaces.
*/
DIRECT,
/**
* Find all directly declared annotations as well as any
* {@link Inherited @Inherited} superclass annotations. This strategy
* is only really useful when used with {@link Class} types since the
* {@link Inherited @Inherited} annotation is ignored for all other
* {@linkplain AnnotatedElement annotated elements}. This strategy does
* not search implemented interfaces.
*/
INHERITED_ANNOTATIONS,
/**
* Find all directly declared and superclass annotations. This strategy
* is similar to {@link #INHERITED_ANNOTATIONS} except the annotations
* do not need to be meta-annotated with {@link Inherited @Inherited}.
* This strategy does not search implemented interfaces.
*/
SUPERCLASS,
/**
* Perform a full search of the entire type hierarchy, including
* superclasses and implemented interfaces. Superclass annotations do
* not need to be meta-annotated with {@link Inherited @Inherited}.
*/
TYPE_HIERARCHY,
/**
* Perform a full search of the entire type hierarchy on the source
* and any enclosing classes. This strategy is similar to
* {@link #TYPE_HIERARCHY} except that {@linkplain Class#getEnclosingClass()
* enclosing classes} are also searched. Superclass annotations do not
* need to be meta-annotated with {@link Inherited @Inherited}. When
* searching a {@link Method} source, this strategy is identical to
* {@link #TYPE_HIERARCHY}.
*/
TYPE_HIERARCHY_AND_ENCLOSING_CLASSES
}
}