java - org.hibernate.exception.JDBCConnectionException : could not fetch initial value for increment generator

Question

在我的应用程序中，我使用两个 hibernate.cfg.xml 文件与同一个 mysql 数据库进行通信。 hibernate cfg 文件是 hibernate.cfg.xml 和 dynamic-hibernate.cfg.xml，我在 JBoss 服务器中部署了我的应用程序。

有时我在使用 Dynamic-hibernate session 插入数据时遇到异常，如 “org.hibernate.exception.JDBCConnectionException:无法获取增量生成器的初始值”。但是我在另一个 Hibernate-cfg.xml session 中没有遇到这个问题。我还延长了 MYsql waittimeout。我仍然面临同样的问题

请帮我解决这个问题。

我的 Dynamic-hibernate-cfg.xml :

<session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/mydatabase</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> 
        <property name="hibernate.default_entity_mode">dynamic-map</property> 
        <property name="hibernate.show_sql">false</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <mapping file="./WEB-INF/xml/DynamicMapping.hbm.xml"/>
    </session-factory>

我的另一个Hibernate-cfg.xml

<session-factory>
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.password">root</property>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/mydatabase</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.hbm2ddl.auto">update</property>
        <property name="hibernate.connection.isolation">2</property>
        <mapping resource="HibernateMapping.hbm.xml" />

    </session-factory>

我的异常(exception)是:

  org.hibernate.exception.JDBCConnectionException: could not fetch initial value for increment generator
        at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:72)
        at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
        at org.hibernate.id.IncrementGenerator.getNext(IncrementGenerator.java:107)
        at org.hibernate.id.IncrementGenerator.generate(IncrementGenerator.java:44)
        at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:91)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)
        at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)
        at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
        at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
        at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:557)
        at org.hibernate.impl.SessionImpl.save(SessionImpl.java:545)

Caused by: java.sql.SQLException: No operations allowed after connection closed.

Connection was closed due to the following exception:

** BEGIN NESTED EXCEPTION ** 

java.sql.SQLException
MESSAGE: Communication link failure: java.io.EOFException, underlying cause: null

** BEGIN NESTED EXCEPTION ** 

java.io.EOFException

STACKTRACE:

java.io.EOFException
    at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1394)
    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:1538)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:1929)

Answer 1

如果您仔细阅读异常，它表示连接已经关闭。检查连接关闭的代码。并检查文件是否正确读取。