query.java

java学习课件

/*查询学生信息程序Query.java*/
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
public class Query implements ActionListener
{ JTextField [] value=new JTextField[6];
  JTextField condition=new JTextField(10);
  JButton queryButton,exitButton;
  JPanel panel1,panel2;
  StudentManager server;
  public Query(StudentManager server,JPanel content) //构造器
  { this.server=server;
    content.setLayout(new GridLayout(2,1));
    for(int i=0;i<value.length; i++) value[i] = new JTextField(30);
    queryButton = new JButton("查询");
    exitButton = new JButton("退出");
    panel1=new JPanel(new GridLayout(4,1));
    panel2=new JPanel(new GridLayout(7,1));
    panel1.add(new JLabel("输入条件如:学号='20060132102'或入学成绩>600等"));
    panel1.add(condition);
    panel1.add(queryButton);
    panel1.add(exitButton);
    panel2.add(new JLabel("---------- 学号---------姓名--出生年月--性别--入学成绩-备注"));
    for(int i=0;i<value.length; i++) panel2.add(value[i]);
    content.add(panel1);
    content.add(panel2);
    queryButton.addActionListener(this);
    exitButton.addActionListener(this);
   }  //构造器结束
  public void actionPerformed(ActionEvent evt) //事件方法
   { 
    Object obj = evt.getSource();
    if(obj == queryButton) 
    {panel1.setVisible(false); //禁止查询条件输入和查询按钮功能,保证本查询完成
     try 
     {String cond=condition.getText().trim();
      if(cond.length()>1) cond=" where "+cond;
      String sqlstr="select * from student_login "+cond;
      Vector vec=server.query(sqlstr); //调用远程方法
      int count=0;
      int elementCount=0;
      while(elementCount<vec.size())
      { String str="";
        for(int i=1; i<=6; i++) 
        { String temp=(String)vec.get(elementCount++); 
          if(temp==null) temp=" ";
          str=str+temp.trim()+"     ";
        }
        value[count].setText(str);
        count++;
        if(count>=value.length)
        { count=0;
          JOptionPane.showMessageDialog(null,"下一屏！","提示信息",JOptionPane.PLAIN_MESSAGE);
        }
       }
       for(;count<value.length;count++) value[count].setText("");
     }	  
	   catch(Exception e) { System.out.println("Error:"+e); } 
	   panel1.setVisible(true);  
  } 
 }
}