connectionURL="jdbc:mysql://localhost:3306/BookDB?user=dbuser;password=aaaaaa"
上面的有问题吗？
日志中的出错信息为：
JDBCStore[/helloapp]: The database connection is null or was found to be closed. Trying to re-open it.

[解决办法]
JDBCStore[/helloapp]: The database connection is null or was found to be closed. Trying to re-open it.

数据库连接为空或者已经被关闭,你的代码怎么写的?你这行代码是打开数据库.
异常信息和你的这行代码是没有关系的.请详细检查代码及根据日志信息来查.