编辑：解决方案：升级到ISIS 1.17.0并设置属性isis.persistor.datanucleus.standaloneCollection.bulkLoad=false解决了前两个问题。
我正在使用Apache ISIS 1.16.2，并且尝试将Blob / Clob内容存储在MariaDB数据库（v10.1.35）中。因此，我使用数据库连接器org.mariadb.jdbc.mariadb-java-client（v2.3.0），并在代码中使用@Persistent批注，如许多示例和ISIS文档所示。
使用下面的代码，我只得到一个名为content_name的单列（其中Blob对象以二进制形式序列化），而不是三列content_name，content_mimetype和content_bytes。
这是具有Blob字段content的Document类：
@PersistenceCapable(identityType = IdentityType.DATASTORE)
@DatastoreIdentity(strategy = IdGeneratorStrategy.IDENTITY, column = "id")
@DomainObject(editing = Editing.DISABLED, autoCompleteRepository = DocumentRepository.class, objectType = "Document")
@Getter
// ...
public class Document implements Comparable<Document> {
@Persistent(
defaultFetchGroup = "false",
columns = {
@Column(name = "content_name"),
@Column(name = "content_mimetype"),
@Column(name = "content_bytes",
jdbcType = "BLOB",
sqlType = "LONGVARBINARY")
})
@Nonnull
@Column(allowsNull = "false")
@Property(optionality = Optionality.MANDATORY)
private Blob content;
// ...
@Column(allowsNull = "false")
@Property
private Date created = new Date();
public Date defaultCreated() {
return new Date();
}
@Column(allowsNull = "true")
@Property
@Setter
private String owner;
// ...
}
这将为DomainObject类
Document创建以下模式，而Blob字段只有一列：CREATE TABLE `document` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`content_name` mediumblob,
`created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`owner` varchar(255) CHARACTER SET latin1 COLLATE latin1_bin DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
通常，ISIS框架的类
org.apache.isis.objectstore.jdo.datanucleus.valuetypes.IsisBlobMapping应该执行映射。但是似乎不包含此Mapper ...1.问题：如何将Blob字段分为三列（如上所述和许多演示项目中所述）。即使我切换到HSQLDB，我仍然只会得到一列，因此MariaDB可能不会有问题。
2.问题：如果我在从另一个DomainObject类继承的类中使用Blob / Clob字段，则通常会得到一个
org.datanucleus.exceptions.NucleusException（堆栈跟踪，请参见下文），并且无法显示其开头或结尾。处理继承有哪些潜在的陷阱？为什么会出现此异常？3.问题：我需要存储属于域对象的文档（您可能已经猜到过）。这样做的正确方法是将文档存储在文件系统树中，而不是数据库中（默认情况下对对象数据也有一些大小限制），然后在对象中引用文件。在Datanucleus documentation中，我发现扩展名
serializeToFileLocation应该可以做到这一点。我通过在Blob字段中添加行@Extension(vendorName="datanucleus", key="serializeToFileLocation" value="document-repository")进行了尝试，但没有任何反应。所以我的问题是：这个Datanucleus扩展与Apache Isis兼容吗？如果此扩展名与Isis冲突，是否可能有
javax.jdo.listener.StoreLifecycleListener或org.apache.isis.applib.AbstractSubscriber将Blob存储在文件系统上，然后再将域对象持久存储到数据库中并在加载之前还原它？有更好的解决方案吗？现在就这样。先感谢您！ ;-)
堆栈跟踪到问题2：
... (other Wicket related stack trace)
Caused by: org.datanucleus.exceptions.NucleusException: Creation of SQLExpression for mapping "org.datanucleus.store.rdbms.mapping.java.SerialisedMapping" caused error
at org.datanucleus.store.rdbms.sql.expression.SQLExpressionFactory.newExpression(SQLExpressionFactory.java:199)
at org.datanucleus.store.rdbms.sql.expression.SQLExpressionFactory.newExpression(SQLExpressionFactory.java:155)
at org.datanucleus.store.rdbms.request.LocateBulkRequest.getStatement(LocateBulkRequest.java:158)
at org.datanucleus.store.rdbms.request.LocateBulkRequest.execute(LocateBulkRequest.java:283)
at org.datanucleus.store.rdbms.RDBMSPersistenceHandler.locateObjects(RDBMSPersistenceHandler.java:564)
at org.datanucleus.ExecutionContextImpl.findObjects(ExecutionContextImpl.java:3313)
at org.datanucleus.api.jdo.JDOPersistenceManager.getObjectsById(JDOPersistenceManager.java:1850)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession.loadPersistentPojos(PersistenceSession.java:1010)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession.adaptersFor(PersistenceSession.java:1603)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession.adaptersFor(PersistenceSession.java:1573)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel$Type$1.loadInBulk(EntityCollectionModel.java:107)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel$Type$1.load(EntityCollectionModel.java:93)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel.load(EntityCollectionModel.java:454)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel.load(EntityCollectionModel.java:70)
at org.apache.wicket.model.LoadableDetachableModel.getObject(LoadableDetachableModel.java:135)
at org.apache.isis.viewer.wicket.ui.components.collectioncontents.ajaxtable.CollectionContentsSortableDataProvider.size(CollectionContentsSortableDataProvider.java:68)
at org.apache.wicket.markup.repeater.data.DataViewBase.internalGetItemCount(DataViewBase.java:142)
at org.apache.wicket.markup.repeater.AbstractPageableView.getItemCount(AbstractPageableView.java:235)
at org.apache.wicket.markup.repeater.AbstractPageableView.getRowCount(AbstractPageableView.java:216)
at org.apache.wicket.markup.repeater.AbstractPageableView.getViewSize(AbstractPageableView.java:314)
at org.apache.wicket.markup.repeater.AbstractPageableView.getItemModels(AbstractPageableView.java:99)
at org.apache.wicket.markup.repeater.RefreshingView.onPopulate(RefreshingView.java:93)
at org.apache.wicket.markup.repeater.AbstractRepeater.onBeforeRender(AbstractRepeater.java:124)
at org.apache.wicket.markup.repeater.AbstractPageableView.onBeforeRender(AbstractPageableView.java:115)
at org.apache.wicket.Component.internalBeforeRender(Component.java:950)
at org.apache.wicket.Component.beforeRender(Component.java:1018)
at org.apache.wicket.MarkupContainer.onBeforeRenderChildren(MarkupContainer.java:1825)
... 81 more
Caused by: org.datanucleus.exceptions.NucleusException: Unable to create SQLExpression for mapping of type "org.datanucleus.store.rdbms.mapping.java.SerialisedMapping" since not supported
at org.datanucleus.store.rdbms.sql.expression.SQLExpressionFactory#newExpression(SQLExpressionFactory.java:189)
at org.datanucleus.store.rdbms.sql.expression.SQLExpressionFactory#newExpression(SQLExpressionFactory.java:155)
at org.datanucleus.store.rdbms.request.LocateBulkRequest#getStatement(LocateBulkRequest.java:158)
at org.datanucleus.store.rdbms.request.LocateBulkRequest#execute(LocateBulkRequest.java:283)
at org.datanucleus.store.rdbms.RDBMSPersistenceHandler#locateObjects(RDBMSPersistenceHandler.java:564)
at org.datanucleus.ExecutionContextImpl#findObjects(ExecutionContextImpl.java:3313)
at org.datanucleus.api.jdo.JDOPersistenceManager#getObjectsById(JDOPersistenceManager.java:1850)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession#loadPersistentPojos(PersistenceSession.java:1010)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession#adaptersFor(PersistenceSession.java:1603)
at org.apache.isis.core.runtime.system.persistence.PersistenceSession#adaptersFor(PersistenceSession.java:1573)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel$Type$1#loadInBulk(EntityCollectionModel.java:107)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel$Type$1#load(EntityCollectionModel.java:93)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel#load(EntityCollectionModel.java:454)
at org.apache.isis.viewer.wicket.model.models.EntityCollectionModel#load(EntityCollectionModel.java:70)
at org.apache.wicket.model.LoadableDetachableModel#getObject(LoadableDetachableModel.java:135)
at org.apache.isis.viewer.wicket.ui.components.collectioncontents.ajaxtable.CollectionContentsSortableDataProvider#size(CollectionContentsSortableDataProvider.java:68)
at org.apache.wicket.markup.repeater.data.DataViewBase#internalGetItemCount(DataViewBase.java:142)
at org.apache.wicket.markup.repeater.AbstractPageableView#getItemCount(AbstractPageableView.java:235)
at org.apache.wicket.markup.repeater.AbstractPageableView#getRowCount(AbstractPageableView.java:216)
at org.apache.wicket.markup.repeater.AbstractPageableView#getViewSize(AbstractPageableView.java:314)
at org.apache.wicket.markup.repeater.AbstractPageableView#getItemModels(AbstractPageableView.java:99)
at org.apache.wicket.markup.repeater.RefreshingView#onPopulate(RefreshingView.java:93)
at org.apache.wicket.markup.repeater.AbstractRepeater#onBeforeRender(AbstractRepeater.java:124)
at org.apache.wicket.markup.repeater.AbstractPageableView#onBeforeRender(AbstractPageableView.java:115)
// <-- 8 times the following lines
at org.apache.wicket.Component#internalBeforeRender(Component.java:950)
at org.apache.wicket.Component#beforeRender(Component.java:1018)
at org.apache.wicket.MarkupContainer#onBeforeRenderChildren(MarkupContainer.java:1825)
at org.apache.wicket.Component#onBeforeRender(Component.java:3916)
// -->
at org.apache.wicket.Page#onBeforeRender(Page.java:801)
at org.apache.wicket.Component#internalBeforeRender(Component.java:950)
at org.apache.wicket.Component#beforeRender(Component.java:1018)
at org.apache.wicket.Component#internalPrepareForRender(Component.java:2236)
at org.apache.wicket.Page#internalPrepareForRender(Page.java:242)
at org.apache.wicket.Component#render(Component.java:2325)
at org.apache.wicket.Page#renderPage(Page.java:1018)
at org.apache.wicket.request.handler.render.WebPageRenderer#renderPage(WebPageRenderer.java:124)
at org.apache.wicket.request.handler.render.WebPageRenderer#respond(WebPageRenderer.java:195)
at org.apache.wicket.core.request.handler.RenderPageRequestHandler#respond(RenderPageRequestHandler.java:175)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor#respond(RequestCycle.java:895)
at org.apache.wicket.request.RequestHandlerStack#execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle#execute(RequestCycle.java:265)
at org.apache.wicket.request.cycle.RequestCycle#processRequest(RequestCycle.java:222)
at org.apache.wicket.request.cycle.RequestCycle#processRequestAndDetach(RequestCycle.java:293)
at org.apache.wicket.protocol.http.WicketFilter#processRequestCycle(WicketFilter.java:261)
at org.apache.wicket.protocol.http.WicketFilter#processRequest(WicketFilter.java:203)
at org.apache.wicket.protocol.http.WicketFilter#doFilter(WicketFilter.java:284)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain#doFilter(ServletHandler.java:1668)
at org.apache.isis.core.webapp.diagnostics.IsisLogOnExceptionFilter#doFilter(IsisLogOnExceptionFilter.java:52)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain#doFilter(ServletHandler.java:1668)
at org.apache.shiro.web.servlet.AbstractShiroFilter#executeChain(AbstractShiroFilter.java:449)
at org.apache.shiro.web.servlet.AbstractShiroFilter$1#call(AbstractShiroFilter.java:365)
at org.apache.shiro.subject.support.SubjectCallable#doCall(SubjectCallable.java:90)
at org.apache.shiro.subject.support.SubjectCallable#call(SubjectCallable.java:83)
at org.apache.shiro.subject.support.DelegatingSubject#execute(DelegatingSubject.java:383)
at org.apache.shiro.web.servlet.AbstractShiroFilter#doFilterInternal(AbstractShiroFilter.java:362)
at org.apache.shiro.web.servlet.OncePerRequestFilter#doFilter(OncePerRequestFilter.java:125)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain#doFilter(ServletHandler.java:1668)
// ... some Jetty stuff
at java.lang.Thread#run(Thread.java:748)
最佳答案
经过研究，我认为问题1和2的问题似乎与this ISIS bug report #1902有关。
简而言之：datanucleus扩展插件解析机制似乎找不到ISIS值类型适配器，因此无法知道如何序列化ISIS的Blob / Clob类型。
根据前面提到的ISIS错误报告，此问题已在1.17.0中修复，因此我正尝试从1.16.2升级到此版本（引入了许多其他问题，但这将是一个额外的主题）。
对于问题3，我发现Minio基本上解决了我的问题，但是对于我的需求来说有点过大了。我将继续寻找其他解决方案以将Blob / Clobs存储到本地文件系统，并牢记Minio ...
更新：
我将项目升级到ISIS版本1.17.0。它解决了我在问题1中的问题（现在我为Blob / Clob对象得到了三列）。
升级无法解决问题2（NucleusException）中的问题。我发现只有在返回具有Blob / Clob字段的DomainObjects列表时（即，如果呈现为独立表时），才会抛出该错误。如果直接进入对象的实体视图，则不会引发任何异常，并且可以查看/修改/下载Blob / Clob内容。
同时，我编写了自己的datanucleus插件，该插件将Blob / Clobs存储为文件系统上的文件。
更新2
我找到了规避org.datanucleus.exceptions.NucleusException: Unable to create SQLExpression for mapping of type "org.apache.isis.objectstore.jdo.datanucleus.valuetypes.IsisClobMapping" since not supported的解决方案。批量加载似乎是一个问题（但我不知道任何详细信息）。
通过属性isis.persistor.datanucleus.standaloneCollection.bulkLoad=false（最初由ISIS原型设置为true）取消批量加载解决了该问题。