我通过使用我的代码获得此错误。我已经测试了单个步骤，它们都在工作。通过单击一个Button，我从textflields和组合框中获取值，并且应该执行一个Sql语句。 Doese有谁知道错误意味着什么？ 谢谢你的帮助
错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at lastplan.VendorRegistration$2.mouseClicked(VendorRegistration.java:404)
at java.awt.AWTEventMulticaster.mouseClicked(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
代码：
private void ReqBtn(){
ReqBnt= new JButton("Request");
ReqBnt.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent arg0) {
if (arg0.getSource() == ReqBnt) {
String VendN = txtVendN.getText();
String VendSN = txtVendSN.getText();
String Ad = txtAd.getText();
String Ads = txtAds.getText();
String City = txtCity.getText();
String Zip = txtZip.getText();
String UID = txtUID.getText();
String Reg = txtReg.getText();
String Rep = txtRep.getText();
String Tel = txtTel.getText();
String Fax = txtFax.getText();
String Mail = txtMail.getText();
String Iban = txtIban.getText();
String Bic = txtBic.getText();
String BInst = txtBInst.getText();
String VendInfo = txtVendInfo.getText();
String Flag = "Y";
String PT = comboPT.getSelectedItem().toString();
String Ctry = comboCtry.getSelectedItem().toString();
try{
try {
String sqlx = "SELECT `Abbreviation 2`, `Country English` From `database`.`country_master` " +
"WHERE `Country English` = '" + Ctry + "'";
PreparedStatement pstx = conn.prepareStatement(sqlx);
ResultSet rs = pstx.executeQuery();
while (rs.next()){
partCode = rs.getString("Abbreviation 2");
}}catch (Exception ex) {
System.out.println("Abbreviation Not Found");
}
String sqlFind = "Select max(substring(`Vendor Code`, 3)) From `database`.`vendor_master`";
try {
PreparedStatement pstFind = conn.prepareStatement(sqlFind);
ResultSet rs = pstFind.executeQuery();
while (rs.next()){
partNo = rs.getInt("Vendor Code");
}}catch (Exception ex) {
partNo = 10001;
}
String VendC = partCode+partNo;
try {
String sqlx = "SELECT `Abbreviation Use`, `Country English` From `database`.`country_master` " +
"WHERE `Country English` = '" + Ctry + "'";
PreparedStatement pstx = conn.prepareStatement(sqlx);
ResultSet rs = pstx.executeQuery();
while (rs.next()){
CtryC = rs.getString("Abbreviation Use");
}}catch (Exception ex) {
System.out.println("Abbreviation Not Found");
}
Calendar currentDate = Calendar.getInstance(); //Get the current date
SimpleDateFormat formatter= new SimpleDateFormat("dd.MM.yyyy HH:mm:ss");
String dateNow = formatter.format(currentDate.getTime());
try {
String sql = "INSERT INTO `database`.`vendor_master`(`Vendor Code`,`Vendor Full Name`,`Vendor Short Name`,"+
"`Address`,`Address Suffix`,`ZIP Code`,`City`,`Country`,`Country Code`,`UID No`,`Registration No`,"+
"`Payment Term`,`Creation Date`,`IBAN`,`BIC`,`Banking Institution`,`Representive`,`Email Address`,"+
"`Telefon No`,`Fax`,`Vendor Information`,`Active Flag`) "+
"Values('"+VendC+"','"+VendN+"','"+VendSN+"','"+Ad+"','"+Ads+"','"+Zip+"','"+City+"','"+Ctry+"','"+CtryC+"','"+
UID+"','"+Reg+"','"+PT+"','"+dateNow+"','"+Iban+"','"+Bic+"','"+BInst+"','"+Rep+"','"+Mail+"','"+Tel+"','"+
Fax+"','"+VendInfo+"','"+Flag+"')";
PreparedStatement pstExecute = conn.prepareStatement(sql);
pstExecute.execute();
System.out.println("Vendor Registred");
}catch (Exception ex) {
System.out.println("Duplicate Data found");
}}catch (Exception ex) {
System.out.println("Duplicate Data found");
}
}
}
});
ReqBnt.setFont(new Font("Arial", Font.BOLD, 13));
ReqBnt.setBounds(889, 602, 123, 29);
frameVendReg.getContentPane().add(ReqBnt);
}