Java Null Pointer Exception for JDBC Connection

Question

I am trying to run a web application that gets a specific length of numbers from a user and checks that against a database (so if the user made a typo, it will makes suggestions as to what key the user actually meant). The problem I am running into is the application won't connect to the database, I get this error:

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java.lang.NullPointerException
at Validator.Validate.checkIDs(Validate.java:410)
at Validator.Validate.getAllValidIds(Validate.java:203)
at Python.WebServlet.processRequest(WebServlet.java:70)
at Python.WebServlet.doPost(WebServlet.java:247)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
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:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1805)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

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Line 410 in Validator.Validate is:

Statement stmt = Conn.createStatement();

Where Conn is a java.sql.Connection variable

Line 203 is a call to the method that does the ^ statement

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java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1701)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1546)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:169)
at Validator.Validate.dbConnect(Validate.java:394)
at Validator.Validate.getAllValidIds(Validate.java:193)
at Python.WebServlet.processRequest(WebServlet.java:70)
at Python.WebServlet.doPost(WebServlet.java:247)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
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:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1805)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

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This is the error I get on my server, if I run it on my local machine it works just fine (it validates the ID). What could be the problem here? Cannot it not locate the com.mysql.jdbc.Driver class? Is that class the issue?

Thanks for the advice/help in advance!

NOTE:

The Validator class is an external jar that is in my class path. It calls on another jar in its class path the contains the com.mysql.jdbc classes, as you can see in the following pictures

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The BugValidator jar contains the mysql-connector jar which has the Drivers class

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Answer 1

From this:

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver

It's pretty clear that you don't have the MySQL driver on your ClassPath. Somewhere in your project, you should have the jar that contains the MySQL driver. If you don't, then you either need to download it to your lib directory, or set up a Maven dependency to it, depending on how your projects dependencies are being handled.

EDIT: In response to your update. All your screenshot shows is that everything is set up fine for compilation within your IDE. But we still don't know where you are running your application from that's giving you this stack trace.

Are you running your app from inside your IDE and getting the stack trace from the console? Are you running it after it's been packaged and seeing the stack trace in some logs?