问题：
连接数据库时报错：
log4j:WARN No appenders could be found for logger (com.mchange.v2.log.MLog).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
java.lang.RuntimeException: 无法从数据源获取连接
at com.eteda.DbConnectionPool.EtedaDbPool.getConnection(EtedaDbPool.java:106)
at com.zdc.MyServer.ZhangWork.UserLogin(ZhangWork.java:3567)
at com.zdc.MyServer.ZhangWork.process(ZhangWork.java:96)
at com.lyw.MyServer.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:50)
at com.lyw.MyServer.catalina.connector.http.Hander.run(Hander.java:14)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:118)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:692)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:140)
at com.eteda.DbConnectionPool.EtedaDbPool.getConnection(EtedaDbPool.java:104)
... 7 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1469)
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:644)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:554)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:758)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:685)
... 9 more
分析：
问题原因在配置文件或者创建jdbc时连接数据库的问题上：
先是执行这句：grant all on lx.* to "zhangdc"@'%';
然后配置上面的文件，就可以了。
下面是自己写的一个测试程序，也能通：
总结：从mysql数据库，换成mariadb后，先是将mysql的jar包换成mariadb-java-client-1.6.4.jar(最后问题解决了，回来测了一下，跟这个没关系)。然后进入数据库执行：
grant all on lx.* to "zhangdc"@'%';后，用zhangdc用户登陆，问题就解决了。
有用提示：
grant all on db_name.* to ‘vincent’@'%';
或者GRANT ALL PRIVILEGES ON db_base.* TO db_user @'%' IDENTIFIED BY 'db_passwd';