今天朋友叫俺去帮忙调一下程序，是Hibernate+MySql的问题，可以向数据库中插入数据，但是在查询的时候，抛出如下异常：
org.hibernate.exception.GenericJDBCException: could not execute query
at org.hibernate.exception.ErrorCodeConverter.handledNonSpecificException(ErrorCodeConverter.java:92)
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:80)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.loader.Loader.doList(Loader.java:1596)
at org.hibernate.loader.Loader.list(Loader.java:1577)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:395)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:271)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:844)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
at com.lk.yk.hibernate.operation.TypeOperation.SelectAll(TypeOperation.java:55)
at com.lk.yk.hibernate.operation.TypeOperation.main(TypeOperation.java:84)
Caused by: com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception:
** BEGIN NESTED EXCEPTION **
java.io.EOFException
STACKTRACE:
java.io.EOFException
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1913)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2304)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3176)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1153)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1266)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:120)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1272)
at org.hibernate.loader.Loader.doQuery(Loader.java:391)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
at org.hibernate.loader.Loader.doList(Loader.java:1593)
at org.hibernate.loader.Loader.list(Loader.java:1577)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:395)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:271)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:844)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
at com.lk.yk.hibernate.operation.TypeOperation.SelectAll(TypeOperation.java:55)
at com.lk.yk.hibernate.operation.TypeOperation.main(TypeOperation.java:84)
** END NESTED EXCEPTION **
Last packet sent to the server was 47 ms ago.
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2515)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2803)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3176)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1153)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1266)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:120)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1272)
at org.hibernate.loader.Loader.doQuery(Loader.java:391)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
at org.hibernate.loader.Loader.doList(Loader.java:1593)
... 7 more
Exception in thread "main" java.lang.NullPointerException
at com.lk.yk.hibernate.operation.TypeOperation.main(TypeOperation.java:84)
这个异常，俺还是第一次碰到过，看了看查询方法，也没有错呀，又重新试了一下，还不同样的情况，看来朋友没有误报，没辙，谁让咱水平浅来呢，走人，到ＧＯＯＧＬＥ上逛去，一查说是驱动ＪＡＲ不对，google确实是好东西，一查就有，呵呵，那个舒服呀，问朋友服务器是用的什么版本的ＭＹＳＱＬ，说是５.0的<其实不是５.0的>，俺就从网上下了一个相应版本的ＪＡＲ，呵呵，俺想这次可行了吧，呵呵，没有想到，不成，还是不行。这下俺是彻底的没辙了，水平浅，那咱找别人，又找了一个哥们过来，三两下，解决了，一问，只不过换了一个版本更底的ＪＡＲ，我那个恨呀。
唠叨这么多，不为别的，呵呵，俺只想在这里给自己敲一下警钟，同样是解决问题，为什么别人能找到问题所在，而咱找不到，应该想想这个问题，虽然工作经验少，但这不应该成为狡辩的理由，应该深刻的反思一下......该去增强一下内功了，
呵呵，不多说了，走人，俺先反思，去练功去了，终有一天俺也会成为一个内功深厚的武林高手的......