类是否有可能inheritance超类的注释

我正在使用Spring Framework事务注释进行事务管理，我有一个注释@Transactional的抽象类，如下所示：

 package org.tts.maqraa.service; import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.Set; import javax.persistence.EntityManager; import javax.persistence.EntityNotFoundException; import javax.persistence.PersistenceContext; import javax.persistence.PersistenceContextType; import javax.persistence.Query; import org.springframework.transaction.annotation.Propagation; import org.springframework.transaction.annotation.Transactional; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Parts of this code have been copied from JARVANA site. * * @author Younis alomoush * */ @Transactional(propagation=Propagation.REQUIRED) public abstract class AbstractMaqraaService implements MaqraaService { private Logger logger = LoggerFactory.getLogger(this.getClass()); private int defaultMaxResults = DEFAULT_MAX_RESULTS; @PersistenceContext(type=PersistenceContextType.TRANSACTION) private EntityManager em; /** * The {@link EntityManager} which is used by all query manipulation and * execution in this DAO. * * @return the {@link EntityManager} */ public EntityManager getEntityManager(){ return em; } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#getTypes() */ public abstract Set<Class> getTypes(); /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#store(java.lang.Object) */ @Transactional(propagation = Propagation.REQUIRED) public  T store(T toStore) { return getEntityManager().merge(toStore); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#remove(java.lang.Object) */ @Transactional(propagation = Propagation.REQUIRED) public void remove(Object toRemove) { toRemove = getEntityManager().merge(toRemove); getEntityManager().remove(toRemove); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#flush() */ @Transactional(propagation = Propagation.REQUIRED) public void flush() { getEntityManager().flush(); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#refresh(java.lang.Object) */ @Transactional(propagation = Propagation.SUPPORTS) public void refresh(Object o) { try { if (o != null) { if (o instanceof java.util.Collection) { for (Iterator i = ((Collection) o).iterator(); i .hasNext();) { try { refresh(i.next()); } catch (EntityNotFoundException x) { // This entity has been deleted - remove it from the // collection i.remove(); } } } else { if (getTypes().contains(o.getClass())) { getEntityManager().refresh(o); } } } } catch (EntityNotFoundException x) { // This entity has been deleted } } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#setDefaultMaxResults(int) */ @Transactional(propagation = Propagation.SUPPORTS) public void setDefaultMaxResults(int defaultMaxResults) { this.defaultMaxResults = defaultMaxResults; } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#getDefaultMaxResults() */ public int getDefaultMaxResults() { return defaultMaxResults; } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByNameSingleResult(java * .lang.String) */ @SuppressWarnings("unchecked") public  T executeQueryByNameSingleResult(String queryName) { return (T) executeQueryByNameSingleResult(queryName, (Object[]) null); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByNameSingleResult(java * .lang.String, java.lang.Object[]) */ @SuppressWarnings("unchecked") public  T executeQueryByNameSingleResult( String queryName, Object... parameters) { Query query = createNamedQuery(queryName, DEFAULT_FIRST_RESULT_INDEX, 1, parameters); return (T) query.getSingleResult(); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByName(java.lang.String) */ public  List executeQueryByName(String queryName) { return executeQueryByName(queryName, DEFAULT_FIRST_RESULT_INDEX, getDefaultMaxResults()); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByName(java.lang.String, * java.lang.Integer, java.lang.Integer) */ public  List executeQueryByName(String queryName, Integer firstResult, Integer maxResults) { return executeQueryByName(queryName, firstResult, maxResults, (Object[]) null); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByName(java.lang.String, * java.lang.Object[]) */ public  List executeQueryByName(String queryName, Object... parameters) { return executeQueryByName(queryName, DEFAULT_FIRST_RESULT_INDEX, getDefaultMaxResults(), parameters); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQueryByName(java.lang.String, * java.lang.Integer, java.lang.Integer, java.lang.Object[]) */ @SuppressWarnings("unchecked") public  List executeQueryByName(String queryName, Integer firstResult, Integer maxResults, Object... parameters) { Query query = createNamedQuery(queryName, firstResult, maxResults, parameters); return query.getResultList(); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#createNamedQuery(java.lang.String, * java.lang.Integer, java.lang.Integer) */ public Query createNamedQuery(String queryName, Integer firstResult, Integer maxResults) { return createNamedQuery(queryName, firstResult, maxResults, (Object[]) null); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#createNamedQuery(java.lang.String, * java.lang.Integer, java.lang.Integer, java.lang.Object[]) */ public Query createNamedQuery(String queryName, Integer firstResult, Integer maxResults, Object... parameters) { Query query = getEntityManager().createNamedQuery(queryName); if (parameters != null) { for (int i = 0; i < parameters.length; i++) { query.setParameter(i + 1, parameters[i]); } } query.setFirstResult(firstResult == null || firstResult  0) query.setMaxResults(maxResults); return query; } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#executeQuery(java.lang.String, * java.lang.Integer, java.lang.Integer, java.lang.Object[]) */ @SuppressWarnings("unchecked") public  List executeQuery(String queryString, Integer firstResult, Integer maxResults, Object... parameters) { Query query = createQuery(queryString, firstResult, maxResults, parameters); return query.getResultList(); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#executeQuery(java.lang.String, * java.lang.Object[]) */ @SuppressWarnings("unchecked") public  List executeQuery(String queryString, Object... parameters) { Query query = createQuery(queryString, DEFAULT_FIRST_RESULT_INDEX, getDefaultMaxResults(), parameters); return query.getResultList(); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQuerySingleResult(java.lang. * String) */ @SuppressWarnings("unchecked") public  T executeQuerySingleResult(String queryString) { return (T) executeQuerySingleResult(queryString, (Object[]) null); } /* * (non-Javadoc) * * @see * org.skyway.spring.util.dao.JpaDao#executeQuerySingleResult(java.lang. * String, java.lang.Object[]) */ @SuppressWarnings("unchecked") public  T executeQuerySingleResult(String queryString, Object... parameters) { Query query = createQuery(queryString, DEFAULT_FIRST_RESULT_INDEX, 1, parameters); return (T) query.getSingleResult(); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#createQuery(java.lang.String, * java.lang.Integer, java.lang.Integer) */ public Query createQuery(String queryString, Integer firstResult, Integer maxResults) { return createQuery(queryString, firstResult, maxResults, (Object[]) null); } /* * (non-Javadoc) * * @see org.skyway.spring.util.dao.JpaDao#createQuery(java.lang.String, * java.lang.Integer, java.lang.Integer, java.lang.Object[]) */ public Query createQuery(String queryString, Integer firstResult, Integer maxResults, Object... parameters) { Query query = getEntityManager().createQuery(queryString); if (parameters != null) { for (int i = 0; i < parameters.length; i++) { query.setParameter(i + 1, parameters[i]); } } query.setFirstResult(firstResult == null || firstResult  0) query.setMaxResults(maxResults); return query; } public final void log(LogLevel logLevel, String message, Object... messageParam) { switch (logLevel) { case TRACE: if (logger.isTraceEnabled()) { logger.trace(message, messageParam); } break; case DEBUG: if (logger.isDebugEnabled()) { logger.debug(message, messageParam); } break; case INFO: if (logger.isInfoEnabled()) { logger.info(message, messageParam); } break; case WARN: if (logger.isWarnEnabled()) { logger.warn(message, messageParam); } break; case ERROR: if (logger.isErrorEnabled()) { logger.error(message, messageParam); } break; default: throw new IllegalArgumentException("Log Level is not defined: " + logLevel); } } public final void log(LogLevel logLevel, String message, Throwable throwable) { switch (logLevel) { case TRACE: if (logger.isTraceEnabled()) { logger.trace(message, throwable); } break; case DEBUG: if (logger.isDebugEnabled()) { logger.debug(message, throwable); } break; case INFO: if (logger.isInfoEnabled()) { logger.info(message, throwable); } break; case WARN: if (logger.isWarnEnabled()) { logger.warn(message, throwable); } break; case ERROR: if (logger.isErrorEnabled()) { logger.error(message, throwable); } break; default: throw new IllegalArgumentException("Log Level is not defined: " + logLevel); } } public enum LogLevel{ TRACE, DEBUG, INFO, WARN, ERROR; } } 

另外，我有另一个具体的课程

 package org.tts.maqraa.service; import java.lang.annotation.Annotation; import java.util.HashSet; import java.util.List; import java.util.Set; import org.tts.maqraa.data.Student; public class StudentsService extends AbstractMaqraaService { @Override public Set<Class> getTypes() { Set<Class> set = new HashSet<Class>(); set.add(Student.class); return set; } public Student registerStudent(Student student) { Annotation [] annotation = StudentsService.class.getAnnotations(); System.out.println(annotation); return this.store(student); } public Student editStudent(Student student){ return this.store(student); } public void deregisterStudent(Student student){ this.remove(student); } public List findAllStudents(){ return this.executeQueryByName("Student.findAll"); } } 

如果你注意到方法注册学生已经提供了代码来检查我真正找到@Transactional注释的注释。

这是一个矛盾，我有另一个链接谈论注释的inheritance，它说根本没有inheritance。

查看此链接： http ： //fusionsoft-online.com/articles-java-annotations.php

任何人都可以帮我解决这个矛盾吗？

Answer 1

注释inheritance的工作方式与方法或字段的inheritance基本相同。

由于您只能通过reflection访问注释，因此Class有两种基本方法：

• getAnnotations()返回当前类及其超类的所有注释
• getDeclaredAnnotations()返回当前类的所有注释

您链接的文章所讨论的问题是Method#getAnnotation(...)访问已定义方法的类的declaredAnnotations() ，如上所述，它只返回该类中定义的注释而不是超类的注释。类。

这意味着如果您覆盖使用@Transactional注释的方法之一，则必须在那里添加注释（或者如果框架也在类注释中查找，它应该找到在AbstractMaqraaService声明的@Transactional ）。

Answer 2

是的，如果注释中添加了@Inherited ，则可以。 例如，@ @Transactional注释具有@Inherited 。

来自文档：

表示自动inheritance注释类型。 如果注释类型声明中存在Inherited元注释，并且用户在类声明上查询注释类型，并且类声明没有此类型的注释，则将自动查询类的超类以获取注释类型。 将重复此过程，直到找到此类型的注释，或者到达类层次结构（对象）的顶部。 如果没有超类具有此类型的注释，则查询将指示相关类没有此类注释。

请注意，如果使用带注释的类型来注释除类之外的任何内容，则此元注释类型不起作用。 另请注意，此元注释仅导致注释从超类inheritance; 已实现接口上的注释无效。

@Transactional的文件：

 @Target(value={METHOD,TYPE}) @Retention(value=RUNTIME) @Inherited @Documented public @interface Transactional 

偏离主题：您不能在Java中对注释进行子类型化。