I have the following code that's trying to establish a connection to a remote database. It's throwing an exception, and I can't figure out why.
import java.util.List;
import java.util.ArrayList;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.ResultSet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import com.model.Bulletin;
Connection connection = getConnection();
Statement statement = connection.createStatement();
private Connection getConnection() {
Connection conn = null;
String url = "jdbc:mysql://address/cpc";
String userName = "user";
String password = "password"; // Don't worry, that's not the real password.
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(url, userName, password);
} catch (Exception e) {
return null;
}
return conn;
}
Can anyone explain to me why I'm getting this exception?
Uncaught exception from servlet
java.lang.reflect.InvocationTargetException
at com.google.appengine.runtime.Request.process-6673c09727e16cea(Request.java)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:43)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:192)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:510)
at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:449)
at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:455)
at com.google.tracing.TraceContext.runInContext(TraceContext.java:695)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:333)
at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:325)
at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:453)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.ExceptionInInitializerError
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:283)
at java.sql.DriverManager.getConnection(DriverManager.java:620)
at java.sql.DriverManager.getConnection(DriverManager.java:200)
at com.dao.BulletinDAO.getConnection(BulletinDAO.java:231)
at com.dao.BulletinDAO.getApprovedBulletins(BulletinDAO.java:134)
at com.action.GetApprovedBulletins.execute(GetApprovedBulletins.java:45)
... 74 more
Caused by: java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:355)
at java.security.AccessController.checkPermission(AccessController.java:567)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
at java.lang.ThreadGroup.checkAccess(ThreadGroup.java:315)
at java.lang.Thread.init(Thread.java:353)
at java.lang.Thread.<init>(Thread.java:437)
at java.util.TimerThread.<init>(Timer.java:478)
at java.util.Timer.<init>(Timer.java:100)
at java.util.Timer.<init>(Timer.java:146)...(length 8258)
jjathman
This is almost certainly because you are missing the jdbc driver jar for MySql. You can find it Here. Unzip it and add the jar to your classpath.
Update: You can not use MySQL with GAE because sockets are not allowed. This will never work for you. They have alternative persistence mechanisms besides MySQL. See: Can I use a MySQL database with an App Engine application
Try this:
try
{ // Load driver class
Class.forName("com.mysql.jdbc.Driver");
}
catch (java.lang.ClassNotFoundException e) {
System.err.println("ClassNotFoundException: " +e);
}
Instead of:
try {
// Exception thrown in next line.
Class.forName(driver).newInstance();
conn = DriverManager.getConnection(url, userName, password);
} catch (Exception e) {
return null;
}
来源：https://stackoverflow.com/questions/11380681/jdbc-java-lang-noclassdeffounderror-could-not-initialize-class-com-mysql-jdb