tomcat启动报：Connection refused

Tomcat启动时报如下错误：
WARN : com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@118d1a82 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: (com.mchange.v2.resourcepool.BasicResourcePool#run ) 2018年05月04日17点02分
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.GeneratedConstructorAccessor52.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1129)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:358)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2498)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2535)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2320)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:834)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46)
at sun.reflect.GeneratedConstructorAccessor45.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:345)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at java.net.Socket.(Socket.java:434)
at java.net.Socket.(Socket.java:244)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:256)
at com.mysql.jdbc.MysqlIO.(MysqlIO.java:308)
... 19 more
说明：
1.刚开始查看mysql的运行状态是关闭的，然后启动mysql，启动成功；
图片说明
2.再次启动tomcat还是失败，然后查看防火墙，发现tomcat的8080端口，和mysql的3306端口未添加进去，然后添加了后重启防火墙，显示添加成功；

3.再次启动还是失败，检查db.properties，测试通过，正确；
4.数据库权限：我的是用root账户连接数据库的，检查数据库发现也都有权限
注：tomcat和mysql在同一服务器中

a)虚拟机centos配置如下：vi /etc/hosts
图片说明
b)关闭防火墙
c）杀死所有进程，重启tomcat
查询tomcat所有进程： ps -ef |grep tomcat
杀死进程：kill -9 端口号
d)可以将web工程中pom的tomcat插件删除在添加然后安装，服务层manager工程中的pom的tomcat插件删除在添加安装
数据库连接问题解决如图：
图片说明

你的mysql端口映射出去的有没有限制啊,然后服务器的防火墙关闭一下确保可以通讯,看下有用不

vi /etc/hosts

    在里边最下方添加一条记录

    格式：外网ip地址   服务器名称（此处为site01）

    例如： 222.222.222.222 site01

     即可

使用ps -eaf | grep tomcat命令查看是否有tomcat进程在使用
如果发现有进程在运行，
则用kill -9 Pid来杀掉这个进程，

参考: https://blog.csdn.net/daxiang12092205/article/details/52071145

用mysql客户端看看能不能连接，能连接就不是mysql或防火墙的问题，不能就看mysql或者防火墙。

tomcat和mysql在同一服务器中，如果是这样的话，你需要在你本地看下是否可以连通，如果本地可以的话，你要不就把你的代码的ip使用127的方式来走；

防火墙、网络、数据库服务器状态，一个一个检查

报错的tomcat在远程linux服务器上，我ping这个服务器的ip地址，ping不同；
这个tomcat里还有另外一个项目，会不会是数据库的连接被沾满了？

兄弟们，错误解决了，是tomcat里的另一个项目的数据库的配置错误，真是日了狗了，搞了一天多的时间！！！
我这c币给lu92649264这位兄弟好了，这哥们走心了啊，虽然不是他给我解决的。