我也碰到过这种,后来解决了:Tomcat5.5 配置MySQL数据源:
必须把以下的四个文件COPY到
C:\tomcat5.5\common\lib和项目的lib下。commons-collections.jar 
commons-pool.jar
commons-dbcp.jar
MySQL JDBC 驱动struts-config.xml<data-sources >
 <data-source key="mysql" type="org.apache.commons.dbcp.BasicDataSource" >
      <set-property property="password" value="mysql" />
      <set-property property="minCount" value="2" />
      <set-property property="maxCount" value="10" />
      <set-property property="username" value="root" />
      <set-property property="driverClassName" value="com.mysql.jdbc.Driver" />
      <set-property property="description" value="MySQL DataSource" />
      <set-property property="url" value="jdbc:mysql://localhost:3306/db_news" />
    
      <set-property property="autoCommit" value="true" />    </data-source>
  </data-sources>myeclipse自动生成的strust-config.xml有几点要注意:
1.driverClassName不是driverclass;
2.username不是user
3.不要设置loginTimeout.
action调用:DataSource ds=getDataSource(request,"mysql");