从MySQL DB检索数据并显示在JTable中 [英] Retrieve Data from MySQL DB and show in JTable

问题描述

我正在使用以下代码从MySQL数据库检索数据.该代码正确连接到数据库.我的问题是从MySQL DB检索数据并将其显示在JTable中.

I am using the following code for retrieving the data from MySQL Database. The code connects to the database properly. My problem is in retrieving the data from MySQL DB and showing it in the JTable.

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
}

执行此代码后，将得到以下输出.我该如何解决我的问题?

When this code is I executed, I get the following output. How can I solve my problem?

*** 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)

推荐答案

我没有看到任何错误.您所看到的是从代码内打印的消息，主要是从以下语句中打印出来的:

I don't see any errors. What you see are the messages that are being printed from within your code, primarily from these statements:

ResultSetMetaData metaDt = results.getMetaData();
System.out.println(metaDt);
int cols = metaDt.getColumnCount();
System.out.println("database" +cols);

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