前几天把程序部署到虚拟主机上，发现方法无法访问数据库。根据关键字查询说事数据表的操作权限在linux上没有权限。但是后来发现其实不是权限问题。是myeclipse的数据表映射工具在生成hbm.xml文件的时候增加了catalog属性。
1，catalog的作用会重新指定数据库
2，所以去除catalog就可以访问数据表了

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数据的配置主要有：

在hibernate连接数据库中：
<prop key="hibernate.hbm2ddl.auto">update</prop> 自动修改数据库中的表
<prop key="hibernate.hbm2ddl.auto">create</prop>自动创建数据库中的表
hibernate.hbm2ddl.auto参数的作用主要用于：自动创建|更新|验证数据库表结构。
create：
每次加载hibernate时都会删除上一次的生成的表，然后根据你的model类再重新来生成新表，哪怕两次没有任何改变也要这样执行，这就是导致数据库表数据丢失的一个重要原因。
create-drop ：
每次加载hibernate时根据model类生成表，但是sessionFactory一关闭,表就自动删除。
update：
最常用的属性，第一次加载hibernate时根据model类会自动建立起表的结构（前提是先建立好数据库），以后加载hibernate时根据model类自动更新表结构，即使表结构改变了但表中的行仍然存在不会删除以前的行。要注意的是当部署到服务器后，表结构是不会被马上建立起来的，是要等应用第一次运行起来后才会。
validate ：
每次加载hibernate时，验证创建数据库表结构，只会和数据库中的表进行比较，不会创建新表，但是会插入新值。


在hibernate配置文件中还要进行配置环境的配置：
<property name="packagesToScan">
<list>
<value>com.*</value>
</list>
</property>

在persistence.xml里边加入如下的设置语句：

<properties>

 <property name="hibernate.hbm2ddl.auto" value="create"/>

 //1：value="create-drop" 表示当JPA应用的时候自动创建表，在解应用的时候删除相应的表，这个在做测试的时候比较有用，但在开发过程中不这么用

//2：value="create"这个在每次应用启动的时候都会创建数据库表（会删除以前数据库里的数据。

//3：value="update" 这个属性的作用是a:每次只会更新数据库表里的信息

b:在entityBean添加或删除字段的时候会同步到数据库中的表

<!--显示最终执行的sql-->

<property name="hibernate.show_sql" value="true"/>

<!--格式化显示最终执行的sql-->

<property name="hibernate.formate_sql" value="true"/>

</properties>