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POJava Null Pointer Exception for JDBC Connection
 

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    <p>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: </p> <hr> <blockquote> <p>java.lang.NullPointerException<br> at Validator.Validate.checkIDs(Validate.java:410)<br> at Validator.Validate.getAllValidIds(Validate.java:203)<br> at Python.WebServlet.processRequest(WebServlet.java:70)<br> at Python.WebServlet.doPost(WebServlet.java:247)<br> at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)<br> at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)<br> at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)<br> at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)<br> at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)<br> at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)<br> at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)<br> at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)<br> at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)<br> at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)<br> at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)<br> at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)<br> at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)<br> at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1805)<br> at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)<br> at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)<br> at java.lang.Thread.run(Thread.java:662)</p> </blockquote> <hr> <p>Line 410 in Validator.Validate is:</p> <pre><code>Statement stmt = Conn.createStatement(); </code></pre> <p>Where Conn is a java.sql.Connection variable</p> <p>Line 203 is a call to the method that does the ^ statement</p> <hr> <blockquote> <p>java.lang.ClassNotFoundException: com.mysql.jdbc.Driver<br> at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1701)<br> at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1546)<br> at java.lang.Class.forName0(Native Method)<br> at java.lang.Class.forName(Class.java:169)<br> at Validator.Validate.dbConnect(Validate.java:394)<br> at Validator.Validate.getAllValidIds(Validate.java:193)<br> at Python.WebServlet.processRequest(WebServlet.java:70)<br> at Python.WebServlet.doPost(WebServlet.java:247)<br> at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)<br> at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)<br> at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)<br> at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)<br> at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)<br> at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)<br> at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)<br> at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)<br> at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)<br> at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)<br> at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)<br> at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)<br> at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)<br> at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)<br> at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1805)<br> at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)<br> at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)<br> at java.lang.Thread.run(Thread.java:662) </p> </blockquote> <hr> <p>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?</p> <p>Thanks for the advice/help in advance!</p> <h2>NOTE:</h2> <p>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</p> <p><img src="https://i.stack.imgur.com/wB9qT.png" alt="Libraries currently in my netbeans project"></p> <hr> <p>The BugValidator jar contains the mysql-connector jar which has the Drivers class</p> <p><img src="https://i.stack.imgur.com/LM56M.png" alt="Contents of the BugValidator jar"></p> <hr> <p><img src="https://i.stack.imgur.com/vn5T3.png" alt="Contents of mysql-connector-java-5.1.7-bin.jar"></p>
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    1. COHave you included the mySQL JDBC driver in your classpath?
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    2. COThe validator class is an external jar and it contains another jar that has the mySQL JDBC driver class in the com.mysql.jdbc folder
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    3. CONested jar files are not included in your classpath. So if you are including `BugValidator.jar`, the jars inside of it will *not* be in the classpath. Make sure that on the server the JDBC driver jar is explicitly in the classpath
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