如何用Hibernate插入新项目? [英] How to insert new items with Hibernate?
问题描述
我有一个名为 Task
的实体类,它映射到hibernate中。
我可以获取现在属于这个类的项目正确,所以我不认为这是类映射的问题。
然而,当我尝试插入一个新项目,我得到以下错误:
org.hibernate.exception.SQLGrammarException:执行孤立工作时出错
at org。 hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:80)
位于org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
位于org.hibernate.engine。 jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
位于org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
位于org.hibernate.engine。 transaction.internal.jdbc.JdbcIsolationDelegate.delegateWork(JdbcIsolationDelegate.java:96)
at org.hib ernate.id.enhanced.TableStructure $ 1.getNextValue(TableStructure.java:131)
at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:58)
at org.hibernate.id .enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:422)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:117)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener .saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener .java:114)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(S
at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:672)
在以下代码中:
任务t =新任务();
t.title =foo;
t.comment =bar;
// snip ...(除了id以外,每个任务域都有一些值)
session.saveOrUpdate(Task,t); //这是发生异常的行
如果我不做 saveOrUpdate()
,那么新任务不会被插入到数据库中。
我做错了什么?
编辑:
session.save(任务)
也不起作用 得到这个工作与这个链接的帮助: http://www.coderanch.com/t/487173/ORM/databases/hibernate-sequence-exist
显然,hibernate会寻找序列表来生成id。设置如下:
@GeneratedValue(strategy = GenerationType.IDENTITY)
关于id,会导致它使用基础数据库的自动增量,而不是尝试生成id本身,现在它可以工作。
I have an entity class called Task
which is mapped in hibernate.
I'm able to fetch existing items belonging to this class correctly, so I don't think this is an issue with the mapping of the class.
However, when I try to insert a new item, I get the following error:
org.hibernate.exception.SQLGrammarException: error performing isolated work
at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:80)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.transaction.internal.jdbc.JdbcIsolationDelegate.delegateWork(JdbcIsolationDelegate.java:96)
at org.hibernate.id.enhanced.TableStructure$1.getNextValue(TableStructure.java:131)
at org.hibernate.id.enhanced.NoopOptimizer.generate(NoopOptimizer.java:58)
at org.hibernate.id.enhanced.SequenceStyleGenerator.generate(SequenceStyleGenerator.java:422)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:117)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:114)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:680)
at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:672)
In the following code:
Task t = new Task();
t.title = "foo";
t.comment = "bar";
//snip... (every single field of task is given some value, except for id)
session.saveOrUpdate("Task", t); //This is the line on which the exception occurs
If I don't do saveOrUpdate()
, then the new task isn't inserted into the db.
What am I doing wrong?
Edit: session.save(task)
doesn't work either
Got this to work with the help of this link: http://www.coderanch.com/t/487173/ORM/databases/hibernate-sequence-exist
Apparently hibernate looks for sequence tables for generating the id. Setting the following:
@GeneratedValue(strategy = GenerationType.IDENTITY)
on the id, causes it to use the underlying db's auto increment and not try to generate the id itself, and now it works.
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