今天在做web项目的时候碰到了这样的一个异常：

Caused by: java.lang.RuntimeException: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)	at edu.gzucm.yjsglxt.base.util.TimeSetUtils.getTimeSets(TimeSetUtils.java:52)	at edu.gzucm.yjsglxt.base.util.TimeSetUtils.(TimeSetUtils.java:22)	... 3 moreCaused by: org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1549)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)	at edu.gzucm.yjsglxt.base.util.TimeSetUtils.getTimeSets(TimeSetUtils.java:32)	... 4 moreCaused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)	at java.lang.reflect.Constructor.newInstance(Unknown Source)	at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)	at com.mysql.jdbc.MysqlIO.(MysqlIO.java:346)	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2334)	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2371)	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2163)	at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:794)	at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)	at java.lang.reflect.Constructor.newInstance(Unknown Source)	at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:378)	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)	at org.apache.tomcat.dbcp.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)	at org.apache.tomcat.dbcp.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545)	... 7 moreCaused by: java.net.ConnectException: Connection refused: connect	at java.net.PlainSocketImpl.socketConnect(Native Method)	at java.net.PlainSocketImpl.doConnect(Unknown Source)	at java.net.PlainSocketImpl.connectToAddress(Unknown Source)	at java.net.PlainSocketImpl.connect(Unknown Source)	at java.net.SocksSocketImpl.connect(Unknown Source)	at java.net.Socket.connect(Unknown Source)	at java.net.Socket.connect(Unknown Source)	at java.net.Socket.(Unknown Source)	at java.net.Socket.(Unknown Source)	at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:254)	at com.mysql.jdbc.MysqlIO.(MysqlIO.java:295)	... 23 more2012-2-19 15:35:27 edu.gzucm.yjsglxt.base.util.InitInfoUtil 严重: nullorg.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1549)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1388)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)	at edu.gzucm.yjsglxt.base.util.DataSourceUtil.getConnection(DataSourceUtil.java:67)	at edu.gzucm.yjsglxt.base.util.InitInfoUtil.(InitInfoUtil.java:265)	at edu.gzucm.yjsglxt.base.filter.PrepareFilter.init(PrepareFilter.java:116)	at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:273)	at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:254)	at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:372)	at org.apache.catalina.core.ApplicationFilterConfig.(ApplicationFilterConfig.java:98)	at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4584)	at org.apache.catalina.core.StandardContext$2.call(StandardContext.java:5262)	at org.apache.catalina.core.StandardContext$2.call(StandardContext.java:5257)	at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)	at java.util.concurrent.FutureTask.run(Unknown Source)	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)	at java.lang.Thread.run(Unknown Source)Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)	at java.lang.reflect.Constructor.newInstance(Unknown Source)	at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)	at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)	at com.mysql.jdbc.MysqlIO.(MysqlIO.java:346)	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2334)	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2371)	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2163)	at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:794)	at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)	at java.lang.reflect.Constructor.newInstance(Unknown Source)	at com.mysql.jdbc.Util.handleNewInstance(Util.java:407)	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:378)	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)	at org.apache.tomcat.dbcp.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)	at org.apache.tomcat.dbcp.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:582)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1556)	at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createPoolableConnectionFactory(BasicDataSource.java:1545)	... 17 moreCaused by: java.net.ConnectException: Connection refused: connect	at java.net.PlainSocketImpl.socketConnect(Native Method)	at java.net.PlainSocketImpl.doConnect(Unknown Source)	at java.net.PlainSocketImpl.connectToAddress(Unknown Source)	at java.net.PlainSocketImpl.connect(Unknown Source)	at java.net.SocksSocketImpl.connect(Unknown Source)	at java.net.Socket.connect(Unknown Source)	at java.net.Socket.connect(Unknown Source)	at java.net.Socket.(Unknown Source)	at java.net.Socket.(Unknown Source)	at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:254)	at com.mysql.jdbc.MysqlIO.(MysqlIO.java:295)	... 33 more2012-2-19 15:35:27 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["http-bio-8080"]2012-2-19 15:35:27 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["ajp-bio-8009"]2012-2-19 15:35:27 org.apache.catalina.startup.Catalina start信息: Server startup in 2983 ms

我知道是连接数据库的时候出现了错误，我检查了我的tomcat的配置文件context.xml文件

配置如下：

 1 
 2 3 Licensed to the Apache Software Foundation (ASF) under one or more
 4 contributor license agreements. See the NOTICE file distributed with
 5 this work for additional information regarding copyright ownership.
 6 The ASF licenses this file to You under the Apache License, Version 2.0
 7 (the "License"); you may not use this file except in compliance with
 8 the License. You may obtain a copy of the License at
 9 
10 http://www.apache.org/licenses/LICENSE-2.0
11 
12 Unless required by applicable law or agreed to in writing, software
13 distributed under the License is distributed on an "AS IS" BASIS,
14 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 See the License for the specific language governing permissions and
16 limitations under the License.
17 -->
18 
19 
20 WEB-INF/web.xml
21 
22 
23 24 
25 -->
26 
27 28 on session expiration as well as webapp lifecycle) -->
29 30 
31 -->
32 33 driverClassName="com.mysql.jdbc.Driver" 
34 maxActive="100" 
35 maxIdle="30" 
36 maxWait="10000" 
37 name="jdbc/mysql" 
38 password="root" 
39 type="javax.sql.DataSource" 
40 url="jdbc:mysql:///yjsglxt?characterEncoding=UTF-8" 
41 username="root"/>
42 

查了一下，才发现原来是url这里有问题：

1 url="jdbc:mysql:///yjsglxt?characterEncoding=UTF-8" 

应该改成：

1 url="jdbc:mysql://localhost:3306/yjsglxt?characterEncoding=UTF-8" 

这样做了以后，再次运行一下项目，嘿嘿，可以了……………………bitsCN.com