Java 如何使用 Hibernate 插入新项目？
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How to insert new items with Hibernate?
提问by Click Upvote
I have an entity class called Taskwhich is mapped in hibernate.
我有一个名为的实体类Task，它在休眠中映射。
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.
我能够正确获取属于此类的现有项目，因此我认为这不是类映射的问题。
However, when I try to insert a new item, I get the following error:
但是，当我尝试插入新项目时，出现以下错误：
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.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:
在以下代码中：
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.
如果我不这样做saveOrUpdate()，则新任务不会插入到数据库中。
What am I doing wrong?
我究竟做错了什么？
Edit: session.save(task)doesn't work either
编辑：session.save(task)也不起作用
采纳答案by Click Upvote
Got this to work with the help of this link: http://www.coderanch.com/t/487173/ORM/databases/hibernate-sequence-exist
在此链接的帮助下得到它：http: //www.coderanch.com/t/487173/ORM/databases/hibernate-sequence-exist
Apparently hibernate looks for sequence tables for generating the id. Setting the following:
显然 hibernate 寻找序列表来生成 id。设置以下内容：
@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.
在 id 上，导致它使用底层数据库的自动增量而不是尝试生成 id 本身，现在它可以工作了。
回答by numsu
If someone else is struggling with this error, I fixed it by removing
如果其他人正在为此错误而苦苦挣扎，我通过删除来修复它
<prop key="hibernate.id.new_generator_mappings">true</prop>
From hibernate properties.
从休眠属性。
回答by lord5et
I accidentally removed hibernate_sequence table in my db. Change:
我不小心删除了数据库中的 hibernate_sequence 表。改变：
spring.jpa.hibernate.ddl-auto=none
to
到
spring.jpa.hibernate.ddl-auto=create
In your application.properties file so Hibernate could recreate this table by himself
在您的 application.properties 文件中，以便 Hibernate 可以自己重新创建此表
