无法使用MySql数据在JTable中显示任何输出 [英] Unable to show any output in a JTable using MySql data
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问题描述
在我的代码中，我没有在Jtable中看到任何输出.
In my code, I am not seeing any output in the Jtable.
在NetBeans中，我在JFrame中有一个JTable，然后创建了一个mysql数据库连接.
In NetBeans, I have a JTable inside a JFrame, then i created a mysql database connection.
在MYSQL中，我以StudentMaster的形式创建了一个表，并将该表中的数据插入JTable中.当我在JTable中选择数据时，它不显示任何输出，也没有错误.
In MYSQL i created a table as StudentMaster and I'm inserting the data from it inside the JTable. when i select the data in JTable, it's not showing any output and there is no error neither.
请帮助我.
public class dbtable extends javax.swing.JFrame {
ResultSet result=null;
Connection conn=null;
Statement st=null;
public dbtable() {
initconn();
initComponents();
}
public Connection initconn(){
try{
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/project", "root", "root");
st = conn.createStatement();
}
catch(Exception e){
System.out.println(e);
}
return conn;
}
public void tab(){
try {
DefaultTableModel model=(DefaultTableModel)jTable1.getModel();
st=conn.createStatement();
String query="Select * from StudentMaster";
result=st.executeQuery(query);
int i=0;
while(result.next())
{
String id=result.getString("StudId");
System.out.println(id);
String no=result.getString("StudNo");
String name=result.getString("StudName");
System.out.println(name);
String stcls=result.getString("StudClass");
String m1=result.getString("StudMrk1");
String m2=result.getString("StudMrk2");
String tot=result.getString("StudTot");
String res=result.getString("StudRes");
model.addRow(new Object[]{id,no,name,stcls,m1,m2,tot,res});
}
jTable1.setModel(model);
result.close();
st.close();
conn.close();
}
catch (Exception e) {
System.out.println(e);
}
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jPanel2 = new javax.swing.JPanel();
CmdA = new javax.swing.JButton();
CmdE = new javax.swing.JButton();
CmdD = new javax.swing.JButton();
CmdX = new javax.swing.JButton();
jPanel3 = new javax.swing.JPanel();
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setFont(new java.awt.Font("Arial", 0, 10));
jPanel1.setBorder(javax.swing.BorderFactory.createMatteBorder(1, 1, 1, 1, java.awt.Color.darkGray));
jPanel2.setBorder(javax.swing.BorderFactory.createMatteBorder(1, 1, 1, 1, java.awt.Color.darkGray));
CmdA.setText("+");
CmdA.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
CmdAActionPerformed(evt);
}
});
CmdE.setText("E");
CmdD.setText("-");
CmdD.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
CmdDActionPerformed(evt);
}
});
CmdX.setMnemonic('Q');
CmdX.setText("Q");
CmdX.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
CmdXActionPerformed(evt);
}
});
javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
jPanel2.setLayout(jPanel2Layout);
jPanel2Layout.setHorizontalGroup(
jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel2Layout.createSequentialGroup()
.addGap(24, 24, 24)
.addComponent(CmdA, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(CmdE, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(CmdD, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addComponent(CmdX, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(25, Short.MAX_VALUE))
);
jPanel2Layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {CmdA, CmdD, CmdE, CmdX});
jPanel2Layout.setVerticalGroup(
jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel2Layout.createSequentialGroup()
.addContainerGap()
.addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE, false)
.addComponent(CmdE, javax.swing.GroupLayout.PREFERRED_SIZE, 70, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(CmdA, javax.swing.GroupLayout.PREFERRED_SIZE, 70, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(CmdD, javax.swing.GroupLayout.PREFERRED_SIZE, 70, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(CmdX, javax.swing.GroupLayout.PREFERRED_SIZE, 70, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(47, 47, 47))
);
jPanel2Layout.linkSize(javax.swing.SwingConstants.VERTICAL, new java.awt.Component[] {CmdA, CmdD, CmdE, CmdX});
jPanel3.setBorder(javax.swing.BorderFactory.createMatteBorder(1, 1, 1, 1, java.awt.Color.darkGray));
jTable1.setModel(new javax.swing.table.DefaultTableModel(
new Object [][] {
{null, null, null, null, null, null, null, null},
{null, null, null, null, null, null, null, null},
{null, null, null, null, null, null, null, null},
{null, null, null, null, null, null, null, null}
},
new String [] {
"ID", "Reg_No", "Name", "Class", "Subj 1", "Subj 2", "Total", "Result"
}
) {
Class[] types = new Class [] {
java.lang.Integer.class, java.lang.Integer.class, java.lang.String.class, java.lang.String.class, java.lang.Integer.class, java.lang.Integer.class, java.lang.Integer.class, java.lang.Integer.class
};
boolean[] canEdit = new boolean [] {
false, false, false, false, false, false, false, false
};
public Class getColumnClass(int columnIndex) {
return types [columnIndex];
}
public boolean isCellEditable(int rowIndex, int columnIndex) {
return canEdit [columnIndex];
}
});
jScrollPane1.setViewportView(jTable1);
jTable1.getColumnModel().getColumn(0).setResizable(false);
jTable1.getColumnModel().getColumn(0).setPreferredWidth(25);
jTable1.getColumnModel().getColumn(1).setResizable(false);
jTable1.getColumnModel().getColumn(1).setPreferredWidth(25);
jTable1.getColumnModel().getColumn(2).setResizable(false);
jTable1.getColumnModel().getColumn(2).setPreferredWidth(250);
jTable1.getColumnModel().getColumn(3).setResizable(false);
jTable1.getColumnModel().getColumn(3).setPreferredWidth(150);
jTable1.getColumnModel().getColumn(4).setResizable(false);
jTable1.getColumnModel().getColumn(4).setPreferredWidth(25);
jTable1.getColumnModel().getColumn(5).setResizable(false);
jTable1.getColumnModel().getColumn(5).setPreferredWidth(25);
jTable1.getColumnModel().getColumn(6).setResizable(false);
jTable1.getColumnModel().getColumn(6).setPreferredWidth(25);
jTable1.getColumnModel().getColumn(7).setResizable(false);
jTable1.getColumnModel().getColumn(7).setPreferredWidth(25);
javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
jPanel3.setLayout(jPanel3Layout);
jPanel3Layout.setHorizontalGroup(
jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 865, Short.MAX_VALUE)
.addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 865, Short.MAX_VALUE))
);
jPanel3Layout.setVerticalGroup(
jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 119, Short.MAX_VALUE)
.addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel3Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 108, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
);
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
.addContainerGap(546, Short.MAX_VALUE)
.addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, 100, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(543, Short.MAX_VALUE))
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(209, 209, 209)
.addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, 95, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(350, Short.MAX_VALUE)))
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap()
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addContainerGap()
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void CmdXActionPerformed(java.awt.event.ActionEvent evt) {
}
private void CmdDActionPerformed(java.awt.event.ActionEvent evt) {
}
private void CmdAActionPerformed(java.awt.event.ActionEvent evt) {
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new dbtable().tab();
new dbtable().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton CmdA;
private javax.swing.JButton CmdD;
private javax.swing.JButton CmdE;
private javax.swing.JButton CmdX;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTable jTable1;
// End of variables declaration
}
推荐答案
生成的代码很难阅读，因此我会尽量避免使用它，特别是如果您是Swing的新手，或者您将有很多代码可以使用不读书也不懂.
Generated code is difficult to read so I would try to avoid it, especially if you're new to Swing or you will have a lot of code that you can't read and don't understand.
话虽这么说，但您的主体中有些臭味:
That being said, your main contains something smelly:
new dbtable().tab();
new dbtable().setVisible(true);
因此，您要创建2个Frame实例；第一个填充了mysql数据，但是从不可见.第二个未填充，但变为可见=>您将看到1个未填充的帧.
So, you're creating 2 instances of your Frame; the first one is populated with mysql data but never made visible. The second one is not populated but made visible => you'll see 1 frame which is not populated.
尝试:
dbtable dbt = new dbtable();
dbt.tab()
dbt.setVisible(true);
BTW:尝试遵守Java命名约定: http://java.about .com/od/javasyntax/a/nameconventions.htm
BTW: try to respect java naming conventions: http://java.about.com/od/javasyntax/a/nameconventions.htm
这篇关于无法使用MySql数据在JTable中显示任何输出的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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