我使用Eclipse编写了一个学生成绩查询子页面,该页面可以通过编译,但是一点击查询按钮"search"调用getTable()方法时就抛出4个错误(用红色字体表示),问题主要出在代码后半部分的方法调用上.
下面是学生成绩查询子页面的全部代码:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*;
import java.util.*;
import java.io.*;
public class Admin
{
public JFrame f;
public JMenuBar aMenuBar;
public JToolBar aToolBar;
public JTable aTable;
public JButton add,delete,search,turnback;
public JMenu manage,set;
public JMenuItem updata, cancel,setDB;
public JScrollPane scrollPane;
public Connection con;
public Statement stmt;
public ResultSet resultset;
public ResultSetMetaData rsMetaData;
public Admin()
{
f=new JFrame("学生成绩查询界面");
aMenuBar=new JMenuBar();
aToolBar=new JToolBar();
manage=new JMenu("管理");
set=new JMenu("设置");
manage.setMnemonic('M');
set.setMnemonic('S');
updata=new JMenuItem("更新数据");
cancel=new JMenuItem("返回");
setDB=new JMenuItem("数据库参数设置");
aMenuBar.add(manage);
aMenuBar.add(set);
manage.add(updata);
manage.add(cancel);
set.add(setDB);
add=new JButton("添加");
delete=new JButton("删除");
search=new JButton("查询");
turnback=new JButton("取消");
aToolBar.setLayout(new FlowLayout(FlowLayout.CENTER));
aToolBar.add(add);
aToolBar.add(delete);
aToolBar.add(search);
aToolBar.add(turnback);
aToolBar.setVisible(false);
//注册事件监听器
turnback.addActionListener(new gotoAdminLogin());
updata.addActionListener(new gotoAdminLogin());
setDB.addActionListener(new gotoAdminLogin());
cancel.addActionListener(new gotoAdminLogin());
search.addActionListener(new gotoAdminLogin());
add.addActionListener(new gotoAdminLogin());
delete.addActionListener(new gotoAdminLogin());
f.setJMenuBar(aMenuBar);
f.getContentPane().add(aToolBar,BorderLayout.NORTH);
f.setSize(400,300);
f.setLocation(300,230);
f.setVisible(true);
//测试数据库连接情况
try
{
//读入配置文件
Properties prop=new Properties();
prop.load(new FileInputStream("db.cfg"));
//获取各项配置参数
String ip=prop.getProperty("DB_IP");
String port=prop.getProperty("DB_PORT");
String username=prop.getProperty("DB_USER_NAME");
String password=prop.getProperty("DB_USER_PWD");
String dbname=prop.getProperty("DB_NAME");
//根据读入的配置参数构建数据库url
String url="jdbc:microsoft:sqlserver://"+ip+":"+port;
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
System.out.println("数据库加载驱动成功");
con=DriverManager.getConnection(url,username,password);
con.setCatalog(dbname);
JOptionPane.showMessageDialog(null, "数据库连接成功!","信息",JOptionPane.INFORMATION_MESSAGE);
}
catch(Exception e)
{
e.printStackTrace();
JOptionPane.showMessageDialog(null, "数据库连接失败!","信息",JOptionPane.INFORMATION_MESSAGE);
}
}
class gotoAdminLogin implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
Object sre=e.getSource();
if(sre==turnback)
{
aToolBar.setVisible(false);
}
else if(sre==cancel)
{
new Admin_Login();
f.setVisible(false);
}
else if(sre==setDB)
{
new setSQLOption();
}
else if(sre==updata)
{
aToolBar.setVisible(true);
}
else if(sre==search)
{
getTable();//报错点1
}
else if(sre==add){}
else if(sre==delete)
{
new DeleteDialog();
}
}
}
public void getTable()
{
try
{
//执行SQL语句
String readSql="SELECT * FROM StudentInfo";
stmt=con.createStatement();
resultset=stmt.executeQuery(readSql);
//在表格中显示查询结果
displayResultSet(resultset);//报错点2
}
catch(SQLException e)
{
e.printStackTrace();
}
}
public void displayResultSet(ResultSet rs)
throws SQLException
{
Vector columnHeads=new Vector();
Vector rows=new Vector();
try {
//获取字段的名称
ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); ++i)
columnHeads.addElement(rsmd.getColumnName(i) );
//获取记录集
do
{
rows.addElement(getNextRow(rs,rsmd));//报错点3
}
while(rs.next());
//在表格中显示查询结果
//创建表格
aTable=new JTable(rows,columnHeads);
scrollPane=new JScrollPane(aTable);
f.getContentPane().add(scrollPane,BorderLayout.CENTER);
scrollPane.setVisible(true);
aTable.setSize(400,150);
}
catch (SQLException sqlex)
{
sqlex.printStackTrace();
}
}
public Vector getNextRow(ResultSet rs, ResultSetMetaData rsmd)
throws SQLException
{
Vector currentRow = new Vector();
for (int i = 1;i <=rsmd.getColumnCount(); ++i )
currentRow.addElement(rs.getString(i));//报错点4
//返回一条记录
return currentRow;
}
public static void main(String args[])
{
new Admin();
}
}
