1.注解的解析轉(zhuǎn)換
通常對注解的解析之后,需要對注解的信息進(jìn)行對象存儲轉(zhuǎn)換,
比如EnableMongoRepositories注解,有13個屬性,如下定義
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@Import(MongoRepositoriesRegistrar.class)
public @interface EnableMongoRepositories {
/**
* Alias for the {@link #basePackages()} attribute. Allows for more concise annotation declarations e.g.:
* {@code @EnableJpaRepositories("org.my.pkg")} instead of {@code @EnableJpaRepositories(basePackages="org.my.pkg")}.
*/
String[] value() default {};
/**
* Base packages to scan for annotated components. {@link #value()} is an alias for (and mutually exclusive with) this
* attribute. Use {@link #basePackageClasses()} for a type-safe alternative to String-based package names.
*/
String[] basePackages() default {};
/**
* Type-safe alternative to {@link #basePackages()} for specifying the packages to scan for annotated components. The
* package of each class specified will be scanned. Consider creating a special no-op marker class or interface in
* each package that serves no purpose other than being referenced by this attribute.
*/
Class<?>[] basePackageClasses() default {};
/**
* Specifies which types are eligible for component scanning. Further narrows the set of candidate components from
* everything in {@link #basePackages()} to everything in the base packages that matches the given filter or filters.
*/
Filter[] includeFilters() default {};
/**
* Specifies which types are not eligible for component scanning.
*/
Filter[] excludeFilters() default {};
/**
* Returns the postfix to be used when looking up custom repository implementations. Defaults to {@literal Impl}. So
* for a repository named {@code PersonRepository} the corresponding implementation class will be looked up scanning
* for {@code PersonRepositoryImpl}.
*
* @return
*/
String repositoryImplementationPostfix() default "Impl";
/**
* Configures the location of where to find the Spring Data named queries properties file. Will default to
* {@code META-INFO/mongo-named-queries.properties}.
*
* @return
*/
String namedQueriesLocation() default "";
/**
* Returns the key of the {@link QueryLookupStrategy} to be used for lookup queries for query methods. Defaults to
* {@link Key#CREATE_IF_NOT_FOUND}.
*
* @return
*/
Key queryLookupStrategy() default Key.CREATE_IF_NOT_FOUND;
/**
* Returns the {@link FactoryBean} class to be used for each repository instance. Defaults to
* {@link MongoRepositoryFactoryBean}.
*
* @return
*/
Class<?> repositoryFactoryBeanClass() default MongoRepositoryFactoryBean.class;
/**
* Configures the name of the {@link MongoTemplate} bean to be used with the repositories detected.
*
* @return
*/
String mongoTemplateRef() default "mongoTemplate";
/**
* Whether to automatically create indexes for query methods defined in the repository interface.
*
* @return
*/
boolean createIndexesForQueryMethods() default false;
/**
* Configures whether nested repository-interfaces (e.g. defined as inner classes) should be discovered by the
* repositories infrastructure.
*/
boolean considerNestedRepositories() default false;
}
2.解析方法
2.1 ImportBeanDefinitionRegistrar接口的registerBeanDefinitions方法中有一個AnnotationMetadata類型的參數(shù),可以調(diào)用getAnnotationAttributes方法來獲取信息
public interface AnnotatedTypeMetadata {
//...
Map<String, Object> getAnnotationAttributes(String annotationName);
2.2 AnnotationAttributes
AnnotationAttributes可以更好的對Map進(jìn)行封裝處理,直接在構(gòu)造函數(shù)中傳入Map實例即可
2.3 AnnotatedElementUtils
可以使用AnnotatedElementUtils的getMergedAnnotationAttributes方法直接返回AnnotationAttributes實例對象
3.基于AnnotationAttributes更好的封裝
比如上面說的EnableMongoRepositories，在實際中轉(zhuǎn)換成對象則是AnnotationRepositoryConfigurationSource,如下代碼
public class AnnotationRepositoryConfigurationSource extends RepositoryConfigurationSourceSupport {
private static final String QUERY_LOOKUP_STRATEGY = "queryLookupStrategy";
private final AnnotationAttributes attributes;
public AnnotationRepositoryConfigurationSource(AnnotationMetadata metadata, Class<? extends Annotation> annotation,
ResourceLoader resourceLoader, Environment environment) {
this.attributes = new AnnotationAttributes(metadata.getAnnotationAttributes(annotation.getName()));
}
public Object getQueryLookupStrategyKey() {
return attributes.get(QUERY_LOOKUP_STRATEGY);
}
}
封裝后,在實際使用時會有更好的體驗
