我尝试注释属性访问器，其返回值是一个映射，如下所示：

@MapKeyColumn(name="parameter_name")
@ElementCollection
public ConcurrentHashMap<String, Serializable> getParameterValues()

这符合hibernate用户指南（第2.2.5.3.4。节）。但是，我得到：

org.hibernate.AnnotationException: Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements: ConfigurationParameterBag.parameterValues
at org.hibernate.cfg.annotations.CollectionBinder.getCollectionBinder(CollectionBinder.java:324)
at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1723)
at org.hibernate.cfg.AnnotationBinder.processIdPropertiesIfNotAlready(AnnotationBinder.java:796)
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:707)
at org.hibernate.cfg.Configuration$MetadataSourceQueue.processAnnotatedClassesQueue(Configuration.java:4035)
at org.hibernate.cfg.Configuration$MetadataSourceQueue.processMetadata(Configuration.java:3989)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1398)
at org.hibernate.cfg.Configuration.generateDropSchemaScript(Configuration.java:1002)
at org.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:130)
at org.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:92)