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POTomcat webapp cannot use MySQL driver after redeploy
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  1. POTomcat webapp cannot use MySQL driver after redeploy
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    copied!<p>I am using commons-dbcp to do connection pooling for a MySQL database in a small Spring webapp which is deployed as a WAR file to a local Tomcat 6.0.28 container (installed using the Ubuntu package manager) using the Sun 1.6 JDK. The deploy is done from Maven using tomcat-maven-plugin-1.1 with the goal <code>tomcat:redeploy</code>. The MySQL Connector/J jar is in the webapp's <code>WEB-INF/lib</code> directory.</p> <p>The first time the webapp is loaded after Tomcat starts, everything works fine. However, when I redeploy the webapp, as Tomcat undeploys the webapp it complains that the JDBC driver was not unregistered.</p> <pre>code>SEVERE: The web application [/taskrun] registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered. Mar 11, 2011 11:29:46 AM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc </pre> <p>Then, when Tomcat restarts the webapp, it fails to connect to the database, complaining about no suitable driver:</p> <pre><code>org.apache.commons.dbcp.SQLNestedException: Cannot create JDBC driver of class 'com.mysql.jdbc.jdbc2.optional.MysqlDataSource' for connect URL 'jdbc:mysql://127.0.0.1:3306/testdb?autoReconnect=true' at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1452) at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371) at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044) at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:113) at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:79) ... 14 more Caused by: java.sql.SQLException: No suitable driver at java.sql.DriverManager.getDriver(DriverManager.java:279) at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1437) ... 18 more </code></pre> <p>Everything works fine if I manually restart Tomcat after the redeploy.</p> <p>I know the MySQL driver registers itself with the DriverManager when the class is loaded, but the <code>com.mysql.jdbc.Driver</code> class doesn't seem to be reloaded when the webapp is redeployed. Is Tomcat's WebappClassLoader supposed to reload classes from the <code>WEB-INF/lib</code> directory when the webapp is reloaded or does it keep them in memory between deploys? Or do I have to re-register the MySQL driver myself after a deploy?</p> <p>Also, I've seen plenty of posts suggesting moving the driver jar to Tomcat's <code>commons/lib</code> directory, but I would like to avoid dependencies external to my WAR file as much as possible. </p> <p>Thank you in advance for any assistance.</p>
 

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