Cannot create JDBC driver of class ” for connect URL ‘null’
On, one of our tomcat boxes in production, we kept getting the following exception when trying to start the server:
17:06:30,823 ERROR SchemaUpdate:134 - could not get database metadata org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null' at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1150) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:880) at org.hibernate.connection.DatasourceConnectionProvider.getConnection(DatasourceConnectionProvider.java:69) at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:27) at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:127) at org.hibernate.impl.SessionFactoryImpl.(SessionFactoryImpl.java:314) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1218) at javax.servlet.GenericServlet.init(GenericServlet.java:212) at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1172) at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:808) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:129) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.ha.tcp.ReplicationValve.invoke(ReplicationValve.java:347) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:619) Caused by: java.lang.NullPointerException at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(JdbcOdbcDriver.java:507) at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(JdbcOdbcDriver.java:476) at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(JdbcOdbcDriver.java:307) at java.sql.DriverManager.getDriver(DriverManager.java:253) at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1143) ... 22 more
Googling for it, only kept suggesting to check our context.xml file, which appeared to be correct. In fact the same war works fine on other instances of tomcat.
All we were doing in our context.xml file is that we’re defining a Data Source Resource. Which gets referred in our Web.xml. Pretty straight forward.
Looking back at the exception, particularly the following part:
org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC driver of class '' for connect URL 'null'
suggests that tomcat was not able to find the Data Source definition which is of course defined in our context.xml file. So certainly there was something to do with Context.xml causing the failure.
On comparing this web app with the other, working tomcat instances, I found Context.xml file was present on both instance in the webapp/<web_app_name>/META-INF dir. Which is fine. But on the working tomcat instance I found another file called <web_app_name>.xml (with the same contents as Context.xml) file under the tomcat/conf/Catalina/localhost folder. This <web_app_name>.xml file was missing on the tomcat instance.
Solution: Copy the Context.xml file to tomcat/conf/Catalina/localhost folder and renaming it to <web_app_name>.xml got rid of the exception. This made it clear why tomcat was throwing this exception and failing to start.
Something was stopping tomcat from creating this file. And of course it turned out to be a tomcat user permission issue. The user under which tomcat was running did not have permission to write to these folders. So we changed the group ownership of tomcat and /etc/tomcat folder to the same group to which the tomcat user belonged and magically everything started working as before.
