processlogin.java

这是一个可以在手机客户端运行的选课系统 这个是客户端

package course.select;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import jdbc.*;
import jdbc.DatabaseConnection;
import java.sql.*;
import exception.*;

public class ProcessLogin extends HttpServlet 
{
		public void doGet(HttpServletRequest req,HttpServletResponse resp) throws IOException 
		{
			processRequest(req,resp);
		}
		
		public void doPost(HttpServletRequest req,HttpServletResponse resp) throws IOException 
		{
			processRequest(req,resp);
		}
		
		protected void processRequest(HttpServletRequest req,HttpServletResponse resp) throws IOException
		{
			String user=req.getParameter("user");
			//保存提交的用户名
			String password=req.getParameter("password");
			//保存提交的密码
			
			
			
			/*
			DatabaseConnection connection=new DatabaseConnection();
			//产生与数据库连接的类的实例，可能抛出SQLException
				
			try
			{
				out.println("before");
				connection.connect();
				out.println("middle");
				password=connection.getPassword(user);
				out.println(password);
				out.println("after");
			}
			catch(ClassNotFoundException e)
			{
				e.printStackTrace(out);
			}
			catch(SQLException e)
			{
				e.printStackTrace(out);
			}
			*/
			
			OutputStream os=resp.getOutputStream();
			DataOutputStream dos=new DataOutputStream(os);
			//获得向MIDlet返回信息的流
			
			try
			{
				if(isValid(user,password))
				//检验密码是否正确
				{					
					dos.writeInt(1);
					//返回提示信息	
				}
			}
			catch(SQLException e)//与数据库连接错误			
			{
				dos.writeInt(-3);
				//-3代表与数据库连接错误
				//返回提示信息
			}
			catch(UserNotExistException e)//用户名不存在
			{
				dos.writeInt(-1);
				//-1代表用户名不存在
				//返回提示信息
			}
			catch(PasswordWrongException e)//密码错误
			{
				dos.writeInt(-2);
				//－2代表密码错误
				//返回提示信息
			}
			catch(DriverException e)
			{
				dos.writeInt(-3);
				//驱动错误属于数据库联接错误
			}
			finally
			{
				dos.close();
			}
			
			
			//调试用代码
			/*
			PrintWriter out=resp.getWriter();
			out.println(user);
			out.println(password);
			 
			
			try
			{
				if(isValid(user,password))
					//检验密码是否正确
					{					
						out.println("correct");
					}
			}
			catch(SQLException e)//与数据库连接错误			
			{
				out.println("SQLException");
			}
			catch(UserNotExistException e)//用户名不存在
			{
				out.println("UserNotExistException");
			}
			catch(PasswordWrongException e)//密码错误
			{
				out.println("PasswordWrongException");
			}
			catch(DriverException e)
			{
				out.println("DriverException");
			}
			finally
			{
				out.close();
			}
			*/
		}
		
		protected boolean isValid(String pUser,String pPassword) throws UserNotExistException,PasswordWrongException,DriverException,SQLException
		{
			//验证用户名与密码
			String user=pUser;
			//保存提交的用户名
			String password=null;
			//保存从数据库中获得的密码
			DatabaseConnection connection=new DatabaseConnection();
			//产生与数据库连接的类的实例，可能抛出SQLException	
			connection.connect();
			if(connection!=null)
				password=connection.getPassword(user);
			//System.out.println(user);	
			//System.out.println(password);
			if(password==null)
				//用户名不存在
				throw new UserNotExistException();
			else
				if(!password.equals(pPassword))
					//密码错误
					throw new PasswordWrongException();
			//connection.close();
			return true;
		}
}