我使用以下代码从MySQL数据库中检索数据。代码正确连接到数据库。我的问题是从MySQL DB中检索数据并在JTable中显示它。
package student;
import java.awt.*;
import javax.swing.*;
import java.awt.*;
import java.sql.*;
import java.util.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.table.*;
public class student1 extends javax.swing.JFrame {
// public Connection Conn;
Vector data = new Vector() ;
Vector columnNames= new Vector();
public student1() {
initComponents();
Connection conn;
}
public void Connection(){
try
{
Class.forName("com.mysql.jdbc.Driver");
String username = "root";
String password = "root";
String Database = "jdbc:mysql://localhost:3306/project";
Connection conn = DriverManager.getConnection(Database, username, password);
System.out.println("*** Connect to the database ***");
String Query = "Select * from StudentMaster";
Statement smnt = conn.createStatement();
ResultSet results = smnt.executeQuery( Query );
ResultSetMetaData metaDt = results.getMetaData();
System.out.println(metaDt);
int cols = metaDt.getColumnCount();
System.out.println("database" +cols);
for(int i=1;i<cols;i++){
columnNames.addElement (metaDt.getColumnName(i));
}
while(results.next()){
Vector row= new Vector(cols);
for(int i=1;i<=cols;i++){
row.addElement(results.getObject(i));
}
data.addElement(row);
}
results.close();
smnt.close();
conn.close();
}
catch(Exception e)
{
System.out.println(e);
}
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jScrollPane1 = new javax.swing.JScrollPane();
jTable1 = new javax.swing.JTable();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
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 [] {
"StudId", "StudNo", "StudName", "StudClass", "StudMrk1", "StudMrk2", "StudTot", "StudRes"
}
){
Class[] types = new Class [] {
java.lang.Integer.class, java.lang.Integer.class, java.lang.String.class, java.lang.Integer.class, java.lang.Integer.class, java.lang.String.class, java.lang.Integer.class, java.lang.String.class
};
public Class getColumnClass(int columnIndex) {
return types [columnIndex];
}
});
jScrollPane1.setViewportView(jTable1);
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()
.addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 560, Short.MAX_VALUE)
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 88, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(212, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new student1().setVisible(true);
student1 s1=new student1();
s1.Connection();
}
});
}
// Variables declaration - do not modify
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JTable jTable1;
// End of variables declaration
}
当我执行此代码时，我得到以下输出。我怎样才能解决我的问题？
*** Connect to the database ***
com.mysql.jdbc.ResultSetMetaData@1194a4e - Field level information:
com.mysql.jdbc.Field@15d56d5[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudId,originalColumnName=StudId,mysqlType=3(FIELD_TYPE_LONG),flags= PRIMARY_KEY, charsetIndex=63, charsetName=US-ASCII]
com.mysql.jdbc.Field@efd552[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudNo,originalColumnName=StudNo,mysqlType=3(FIELD_TYPE_LONG),flags=, charsetIndex=63, charsetName=US-ASCII]
com.mysql.jdbc.Field@19dfbff[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudName,originalColumnName=StudName,mysqlType=253(FIELD_TYPE_VAR_STRING),flags=, charsetIndex=8, charsetName=Cp1252]
com.mysql.jdbc.Field@10b4b2f[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudClass,originalColumnName=StudClass,mysqlType=253(FIELD_TYPE_VAR_STRING),flags=, charsetIndex=8, charsetName=Cp1252]
com.mysql.jdbc.Field@750159[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudMrk1,originalColumnName=StudMrk1,mysqlType=3(FIELD_TYPE_LONG),flags=, charsetIndex=63, charsetName=US-ASCII]
com.mysql.jdbc.Field@1abab88[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudMrk2,originalColumnName=StudMrk2,mysqlType=3(FIELD_TYPE_LONG),flags=, charsetIndex=63, charsetName=US-ASCII]
com.mysql.jdbc.Field@18a7efd[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudTot,originalColumnName=StudTot,mysqlType=3(FIELD_TYPE_LONG),flags=, charsetIndex=63, charsetName=US-ASCII]
com.mysql.jdbc.Field@1971afc[catalog=project,tableName=StudentMaster,originalTableName=studentmaster,columnName=StudRes,originalColumnName=StudRes,mysqlType=253(FIELD_TYPE_VAR_STRING),flags=, charsetIndex=8, charsetName=Cp1252]
database8
BUILD SUCCESSFUL (total time: 14 seconds)
答案 0 :(得分：3)
我没有看到任何错误。您所看到的是从您的代码中打印的消息，主要来自这些语句：
ResultSetMetaData metaDt = results.getMetaData();
System.out.println(metaDt);
int cols = metaDt.getColumnCount();
System.out.println("database" +cols);
答案 1 :(得分：0)
您的基本代码看起来很合理。您创建了两个包含列名称和数据的向量，但是没有在哪里使用这些向量来创建DefaultTableModel，然后可以将其添加到表中。
所以你的代码应该是这样的：
conn.close();
DefaultTableModel model = new DefaultTableModel(data, columnNames);
table.setModel( model );
有关完整示例（使用Access），请查看Table From Database中的Table From Database Example。