kechengbean.java

JSP开发的学生信息管理系统

package kecheng;
import conn.DataBaseConnection;
import java.sql.*;
import java.util.*;
import java.io.*;
public class KechengBean
{
	private Connection con=null;
	public KechengBean()
	{
		this.con=DataBaseConnection.getConnection();
	}
	
	//课程是否存在
	public boolean existKecheng(Kecheng kecheng) {
        try {
            String courseId= kecheng.getCourseId();
            String courseName= kecheng.getCourseName();
            PreparedStatement pstmt = con.prepareStatement(
                    "select courseId,courseName from kecheng where courseId='" +
                    courseId + "' or courseName='"+courseName+"'");
            ResultSet rst = pstmt.executeQuery();
            if (rst.next()) {
                return true;
            }
        } catch (Exception ex) {
            return false;
        }
        return false;
    }
    
	//插入
	public String addKecheng(Kecheng kecheng)
	{
		PreparedStatement pstmt=null;
		String str="";
		try
		{
			if (existKecheng(kecheng)) {
                return "exist"; //存在此课程
            }
			pstmt=con.prepareStatement("insert into kecheng values(?,?,?,?,?)");
			pstmt.setString(1,kecheng.getCourseId());
			pstmt.setString(2,kecheng.getCourseName());
			pstmt.setInt(3,kecheng.getXuefen());
			pstmt.setString(4,kecheng.getCourseType());
			pstmt.setString(5,"1");
			pstmt.execute();
			str="sucess";
		}catch(SQLException ex)
  	    	{
  	    		System.err.println(ex.getMessage());
  	    		str="failer";
  	    	}
  	    	finally
  	    	{
  	    		try{	
  	    		 if(pstmt!=null){
  	    		 	pstmt.close();
  	    		 }
  	    		 if(con!=null){
  	    		 	con.close();
  	    		 }
  	    		 
  	    		}catch(Exception e)
  	    		{
  	    			e.printStackTrace();
  	    		}
  	    	
  	    	}
  	    return str;
	}
	//更新
	public String updateKecheng(Kecheng kecheng)
	{
		PreparedStatement pstmt=null;
		String str="";
		try
		{
			pstmt=con.prepareStatement("update kecheng set courseName=?,xuefen=?,courseType=? where courseId=?");
			pstmt.setString(1,kecheng.getCourseName());
			pstmt.setInt(2,kecheng.getXuefen());
			pstmt.setString(3,kecheng.getCourseType());
			pstmt.setString(4,kecheng.getCourseId());
			pstmt.execute();
			str="sucess";
		}
		catch(SQLException ex)
  	    	{
  	    		System.err.println(ex.getMessage());
  	    		str="failer";
  	    	}
  	    	finally
  	    	{
  	    		try{	
  	    		 if(pstmt!=null){
  	    		 	pstmt.close();
  	    		 }
  	    		 if(con!=null){
  	    		 	con.close();
  	    		 }
  	    		}catch(Exception e)
  	    		{
  	    			e.printStackTrace();
  	    		}
  	    	
  	    	}
  	    return str;	
	}
	
	//删除
	public String deleteKecheng(String courseId)
	{
		PreparedStatement pstmt=null;
		String str="";
		try
		{
			pstmt=con.prepareStatement("update kecheng set flag=? where courseId=?"); 
			pstmt.setString(1,"2");
			pstmt.setString(2,courseId);
			pstmt.execute();
			str="sucess";
		}
		catch(SQLException ex)
  	    	{
  	    		System.err.println(ex.getMessage());
  	    		str="failer";
  	    	}
  	    	finally
  	    	{
  	    		try{	
  	    		 if(pstmt!=null){
  	    		 	pstmt.close();
  	    		 }
  	    		 if(con!=null){
  	    		 	con.close();
  	    		 }
  	    		}catch(Exception e)
  	    		{
  	    			e.printStackTrace();
  	    		}
  	    	
  	    	}
  	    return str;	
	}
	//查询
	public ResultSet executeQuery(String sql)
  	{
  	     Statement stmt=null;
  	     ResultSet rst=null;
  	     try{
	  	      stmt=con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
	  	      rst=stmt.executeQuery(sql);
  	    	}catch(SQLException ex)
  	    	{
  	    		System.err.println(ex.getMessage());
  	    	}
  	    	return rst;
  	 }
  	 //关闭
  	 public void close() 
        {
        	try{
        		if(con!=null){
        			con.close();
        		}
        		
        	}
        	catch(SQLException e)
        	{
        	   e.printStackTrace();	
        	}
        	
        } 
        
     //所有课程
     public String getAllCourse()
  {
  	PreparedStatement pstmt = null;
    ResultSet rst = null;
    StringBuffer sBuf=new StringBuffer();
    try {
      pstmt = con.prepareStatement("select courseId,courseName from kecheng");
          
      rst = pstmt.executeQuery();
      while(rst.next()) { 
      	String courseId= rst.getString("courseId");
        String courseName= rst.getString("courseName");
        sBuf.append("<option value='"+courseId+"'>"+courseName+"</option>\n");
        }
    }
    catch (SQLException ex) {
      return "";
    }
    finally
    {
    	try{
    		if(rst!=null){
    			rst.close();
    			}		
  	    	if(pstmt!=null){
  	    		pstmt.close();
  	    		}
  	    	if(con!=null){
  	    		con.close();
  	    	}	
  	    	
  	    	}catch(Exception e)
    		{
    			e.printStackTrace();
    		}
    }
    return sBuf.toString();
  }   
}