Tomcat 7.0 Connection pooling - jdbc driver exception

Question

I want to implement connection pooling on my Tomcat server. Here is my context.xml file (placed under WebContent/META-INF/context.xml:

<Context path="/evappserver" reloadable="true">
    <Resource
          name="jdbc/evapp"
          auth="Container"
          type="javax.sql.DataSource"
          factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
          initialSize="34"
          maxActive="377"
          maxIdle="233"
          minIdle="89"
          timeBetweenEvictionRunsMillis="34000"
          minEvictableIdleTimeMillis="55000"
          validationQuery="SELECT 1"
          validationInterval="34"
          testOnBorrow="true"
          removeAbandoned="true"
          removeAbandonedTimeout="55"
          username="root"
          password=""
          driverClassName="com.mysql.jdbc.Driver"
          url="jdbc:mysql://localhost:3306/evapp?allowMultiQueries=true"
     />
</Context> 

I have a maven project so the mysql jdbc driver is imported via the pom.xml file, like this:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.6</version>
</dependency>

Here is my java code which throws the exception:

    Context initContext  = new InitialContext();
    Context envContext  = (Context) initContext.lookup("java:/comp/env");
    dataSource = (DataSource) envContext.lookup("jdbc/evapp"); //here is the exception

Here is the exception:

May 13, 2014 10:39:58 AM org.apache.naming.NamingContext lookup
WARNING: Unexpected exception resolving reference
java.sql.SQLException: com.mysql.jdbc.Driver
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:254)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:182)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:702)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:634)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:488)
    at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:144)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:116)
    at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:103)
    at org.apache.tomcat.jdbc.pool.DataSourceFactory.createDataSource(DataSourceFactory.java:539)
    at org.apache.tomcat.jdbc.pool.DataSourceFactory.getObjectInstance(DataSourceFactory.java:237)
    at org.apache.naming.factory.ResourceFactory.getObjectInstance(ResourceFactory.java:143)
    at javax.naming.spi.NamingManager.getObjectInstance(NamingManager.java:321)
    at org.apache.naming.NamingContext.lookup(NamingContext.java:843)
    at org.apache.naming.NamingContext.lookup(NamingContext.java:154)
    at org.apache.naming.NamingContext.lookup(NamingContext.java:831)
    at org.apache.naming.NamingContext.lookup(NamingContext.java:168)
    at com.evappserver.dblayer.DBType.<init>(DBType.java:62)
    at com.evappserver.dblayer.MySqlDB.<init>(MySqlDB.java:16)
    at com.evappserver.logiclayer.BaseLogic.getMainDbConnection(BaseLogic.java:19)
    at com.evappserver.logiclayer.PasswordLoginLogic.doLogin(PasswordLoginLogic.java:27)
    at com.evappserver.servlets.PasswordLoginServlet.doGet(PasswordLoginServlet.java:37)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
    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:722)
Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:266)
    at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:246)
    ... 38 more

Is there something wrong with this configuration?

Answer 1

I think you should include the driver for MySQL in your tomcat /lib folder instead of deploying it along with your web application. This way the server will find the proper classes to instantiate your connection pool and everything should go fine.

Answer 2

check if the classpath of your project contains the file mysql-connector-java-5.1.6.jar. Did maven run without problems?

Answer 3

I had this same problem. For a reason unknown to me, putting the mysql-connector-java*.jar in WEB-INF/lib no longer works in Ubuntu LTS 14.04

I solved it by copying this file (and this file alone) to /usr/share/tomcat7/lib and restarted tomcat7 as a service service tomcat7 restart and everything sprang to life.

Best of luck