Java MySQL - Unknown Null Pointer Exception in simple MySQL Login Frame -

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i have simple login screen connects mysql database. connects fine, throws null pointer exception when tries execute. here 2 snippets of code stack trace. bolded line exception being thrown.

package gui;  import java.sql.*; import javax.swing.joptionpane; import java.awt.event.*;  public class loginframe extends javax.swing.jframe {      connection con;     statement st;     resultset rs;      // login constructor     public loginframe()     {         connect();         initcomponents();         setlocationrelativeto(null);     }      public void connect(){          try         {             con = drivermanager.getconnection(                     "jdbc:mysql://instance44668.db.xeround.com:5719/obliquedb?"                     + "user=name2&password=pass");         }         catch (sqlexception ex)         {             system.err.println("cannot connect database server");             system.err.println(ex.getmessage());         }                  {             try             {                 con.close();             }              catch (sqlexception ex)             {                 system.out.println("better luck next time");             }         }      }

and here method executes statement

private void acceptbuttonactionperformed(java.awt.event.actionevent evt)                                              {                                                      try          {              string user = usertextfield.gettext().trim();             char[] password = passwordtextfield.getpassword();             string pass = new string(password);              string query = "select username,password users username = '"+user+"'and password = '"+pass+"'";    exception thrown-**rs = st.executequery(query);**              int count = 0;             while(rs.next())             {                 count++;             }              if(count == 1) {                 joptionpane.showmessagedialog(this,                          "login successful",                          "error message", joptionpane.error_message);             }             else if(count > 1) {                 joptionpane.showmessagedialog(this,                          "duplicate records found!",                          "error message", joptionpane.error_message);             }             else {                 joptionpane.showmessagedialog(this,                          "user not found",                          "error message", joptionpane.error_message);             }          }         catch (exception e) {             system.out.println("error retrieving records" + e);     }                                             }

and stack trace

error retrieving recordsjava.lang.nullpointerexception java.lang.nullpointerexception     @ gui.loginframe.acceptbuttonactionperformed(loginframe.java:178)     @ gui.loginframe.access$000(loginframe.java:7)     @ gui.loginframe$1.actionperformed(loginframe.java:94)     @ javax.swing.abstractbutton.fireactionperformed(abstractbutton.java:2018)     @ javax.swing.abstractbutton$handler.actionperformed(abstractbutton.java:2341)     @ javax.swing.defaultbuttonmodel.fireactionperformed(defaultbuttonmodel.java:402)     @ javax.swing.defaultbuttonmodel.setpressed(defaultbuttonmodel.java:259)     @ javax.swing.plaf.basic.basicbuttonlistener.mousereleased(basicbuttonlistener.java:252)     @ java.awt.component.processmouseevent(component.java:6505)     @ javax.swing.jcomponent.processmouseevent(jcomponent.java:3321)     @ java.awt.component.processevent(component.java:6270)     @ java.awt.container.processevent(container.java:2229)     @ java.awt.component.dispatcheventimpl(component.java:4861)     @ java.awt.container.dispatcheventimpl(container.java:2287)     @ java.awt.component.dispatchevent(component.java:4687)     @ java.awt.lightweightdispatcher.retargetmouseevent(container.java:4832)     @ java.awt.lightweightdispatcher.processmouseevent(container.java:4492)     @ java.awt.lightweightdispatcher.dispatchevent(container.java:4422)     @ java.awt.container.dispatcheventimpl(container.java:2273)     @ java.awt.window.dispatcheventimpl(window.java:2713)     @ java.awt.component.dispatchevent(component.java:4687)     @ java.awt.eventqueue.dispatcheventimpl(eventqueue.java:707)     @ java.awt.eventqueue.access$000(eventqueue.java:101)     @ java.awt.eventqueue$3.run(eventqueue.java:666)     @ java.awt.eventqueue$3.run(eventqueue.java:664)     @ java.security.accesscontroller.doprivileged(native method)     @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:76)     @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:87)     @ java.awt.eventqueue$4.run(eventqueue.java:680)     @ java.awt.eventqueue$4.run(eventqueue.java:678)     @ java.security.accesscontroller.doprivileged(native method)     @ java.security.protectiondomain$1.dointersectionprivilege(protectiondomain.java:76)     @ java.awt.eventqueue.dispatchevent(eventqueue.java:677)     @ java.awt.eventdispatchthread.pumponeeventforfilters(eventdispatchthread.java:211)     @ java.awt.eventdispatchthread.pumpeventsforfilter(eventdispatchthread.java:128)     @ java.awt.eventdispatchthread.pumpeventsforhierarchy(eventdispatchthread.java:117)     @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:113)     @ java.awt.eventdispatchthread.pumpevents(eventdispatchthread.java:105)     @ java.awt.eventdispatchthread.run(eventdispatchthread.java:90)

in connect connection closed.

the statement better should preparedstatement (having miscellaneous advantages).

so create statement in connect , remove finally.

make disconnect called on application exit closing statement , connection.

the result set rs should close too.

       string query = "select username,password "            + "from users "            + "where binary username = ? "            + "and binary password = ?";

for case sensitive comparison, either specify binary collation columns, or use binary.

passwords can handled more appropiately, talking desk top application it's fine.


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