Hibernate 映射同一MYSQL服务器的多个数据库的方法和问题，待解决

 MYSQL数据库

hibernate.cfg.xml文件的url：

 

<property name="connection.url">
   jdbc:mysql://192.168.1.100:3306/
</property>

 

table映射文件

 

YourTable.hbm.xml

<class name="com.YourTableClass" table="YourTable" catalog="YourDatabase">

 

这样两个影射到不同数据库的Dao都可以select,delete,update Mysql相对应的表

 

但是在insert时可能出现异常，情况如下

表主键 auto_increment

当使用getSession().save();插入时

hebernate会select max(id) from yourtable;然后异常产生

exception

javax.servlet.ServletException: org.hibernate.exception.GenericJDBCException: could not fetch initial value for increment generatororg.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:523)org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)javax.servlet.http.HttpServlet.service(HttpServlet.java:690)javax.servlet.http.HttpServlet.service(HttpServlet.java:803)com.gua.util.FilterEncoding.doFilter(FilterEncoding.java:71)

root cause

org.hibernate.exception.GenericJDBCException: could not fetch initial value for increment generatororg.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:103)org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:91)org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)org.hibernate.id.IncrementGenerator.getNext(IncrementGenerator.java:107)org.hibernate.id.IncrementGenerator.generate(IncrementGenerator.java:44)org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:91)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:530)org.hibernate.impl.SessionImpl.save(SessionImpl.java:518)org.hibernate.impl.SessionImpl.save(SessionImpl.java:514)com.gua.dao.PolicyDAO.save(PolicyDAO.java:44)com.gua.bo.PolicyBO.addPolicy(PolicyBO.java:15)com.gua.struts.action.PolicyAction.performAddPolicy(PolicyAction.java:173)com.gua.struts.action.PolicyAction.execute(PolicyAction.java:60)org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)javax.servlet.http.HttpServlet.service(HttpServlet.java:690)javax.servlet.http.HttpServlet.service(HttpServlet.java:803)com.gua.util.FilterEncoding.doFilter(FilterEncoding.java:71)

root cause

java.sql.SQLException: No database selectedcom.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2928)com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1571)com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1666)com.mysql.jdbc.Connection.execSQL(Connection.java:2994)com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:936)com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1030)com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76)org.hibernate.id.IncrementGenerator.getNext(IncrementGenerator.java:85)org.hibernate.id.IncrementGenerator.generate(IncrementGenerator.java:44)org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:91)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:186)org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:175)org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:530)org.hibernate.impl.SessionImpl.save(SessionImpl.java:518)org.hibernate.impl.SessionImpl.save(SessionImpl.java:514)com.gua.dao.PolicyDAO.save(PolicyDAO.java:44)com.gua.bo.PolicyBO.addPolicy(PolicyBO.java:15)com.gua.struts.action.PolicyAction.performAddPolicy(PolicyAction.java:173)com.gua.struts.action.PolicyAction.execute(PolicyAction.java:60)org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)javax.servlet.http.HttpServlet.service(HttpServlet.java:690)javax.servlet.http.HttpServlet.service(HttpServlet.java:803)com.gua.util.FilterEncoding.doFilter(FilterEncoding.java:71)

url改回  jdbc:mysql://192.168.1.100:3306/db 使用单数据库映射一切正常，异常原因不确定，待解决

如果只是查改删的需求例如审计，这种方法还是可以使用的