JAVA学生管理系统 第7页

JAVA学生管理系统 第7页
import java.util.*;
import java.sql.*;
import javax.swing.*;

/**
 * 用来保存成绩查询方面的类
 */
public class csBean {
 String sql;
 ResultSet rs;
 Vector tempvector=new Vector(1,1);

 String cNum;
 String sNum;
 float grade;

 int colNum;

 /**
  * 添加学生的选课信息
  */
 public void csAdd(String cnum, String snum){
  
  Database DB = new Database();

  this.cNum = cnum;
  this.sNum = snum;
  
  sql = "insert into sc(cnum,snum) values ("+Integer.parseInt(cNum)+","+Integer.parseInt(sNum)+")";
  try{
   DB.OpenConn();
   DB.executeUpdate(sql);
   JOptionPane.showMessageDialog(null,"成功添加一条新的纪录！");

  }
  catch(Exception e){
   JOptionPane.showMessageDialog(null, "保存失败", "错误", JOptionPane.ERROR_MESSAGE);
  }
  finally {
   DB.closeStmt();
   DB.closeConn();
  }
 }

 /**
  * 修改学生的选课成绩
  */
 public void csModify(String cnum, String snum, String grade){
  Database DB = new Database();
  this.cNum = cnum;
  this.sNum = snum;

  try{
   this.grade = Float.parseFloat(grade);
  }
  catch(Exception e){
   JOptionPane.showMessageDialog(null, "成绩输入错误", "错误", JOptionPane.ERROR_MESSAGE);
   return;
  }

  sql = "update sc set grade = "+grade+" where snum = "+Integer.parseInt(sNum)+" and cnum = "+Integer.parseInt(cNum)+" ";
  try{
   DB.OpenConn();
   DB.executeUpdate(sql);
   JOptionPane.showMessageDialog(null,"成功登记成绩！");
  }
  catch(Exception e){
   System.out.println(e);
   JOptionPane.showMessageDialog(null, "登记失败", "错误", JOptionPane.ERROR_MESSAGE);
  }
  finally {
   DB.closeStmt();
   DB.closeConn();
  }
 }

 /**
  * 根据学号搜索其所选的课程名称
  */
 public String[] cNameSearch(String snum){
  Database DB = new Database();
  this.sNum = snum;

  sql = "select * from sc,course where sc.snum = "+Integer.parseInt(sNum)+" and sc.cnum = course.cnum";
  String[] cn = null;
  int row = 0;
  int i = 0;
  
  try{
   DB.OpenConn();
   rs = DB.executeQuery(sql);
   if(rs.last()){
    row = rs.getRow();
   }
   if(row == 0){
    cn = null;
   }
   else{
    cn = new String[row];
    rs.first();
    rs.previous();
    while(rs.next()){
     cn[i] = rs.getString(5);
     i++;
    }
   }
  }
  catch(Exception e){
  }
  finally {
   DB.closeStmt();
   DB.closeConn();
  }
  return cn;
 }

 /**
  * 成绩信息综合查询
  */
 public String[][] csAllSearch(String snum, int colnum){
  this.sNum = snum;
  this.colNum = colnum;
  
  Database DB = new Database();
  String[][] cn = null;
  int row = 0;
  int i = 0;
  sql = "select * from sc,course,student where sc.snum = "+Integer.parseInt(sNum)+" and sc.cnum = course.cnum and sc.snum = student.snum";
  try{
   DB.OpenConn();
   rs = DB.executeQuery(sql);

   if(rs.last()){
    row = rs.getRow();
   }
   if(row == 0){
    cn = null;
   }
   else{
    cn = new String[row][colNum];
    rs.first();
    rs.previous();
    while(rs.next()){
     cn[i][0] = rs.getString(1);
     cn[i][1] = rs.getString(11);
     cn[i][2] = rs.getString(2);
     cn[i][3] = rs.getString(5);
     cn[i][4] = rs.getString(3);
     i++;    }   }  }
  catch(Exception e){  }
  finally {   DB.closeStmt();   DB.closeConn();  }
  return cn; }}

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