userdao.java

JSP+servlet 登陆注册模块还可以进行信息的修改

package com.weishuang.dao;

import com.weishuang.exception.UnknownDBException;
import com.weishuang.exception.UserExistException;
import com.weishuang.iface.Constant;
import com.weishuang.pojo.User;
import com.weishuang.util.DBConn;

import java.sql.*;
public class UserDAO {
	private Connection conn=null;
	private PreparedStatement pstmt;
	private ResultSet rs;
	public UserDAO(){
		try {
			conn=new DBConn().getConnection(Constant.ACCESS_DB);
		} catch (UnknownDBException e) {
			e.printStackTrace();
		}
	}
	public boolean regist(User u) throws UserExistException{
		boolean exist=isExist(u);
		System.out.println(exist);
		if(exist) 
			throw new UserExistException("该用户名已存在");
		else
		{
			String sql="insert into user(username,password) values(?,?)";
			try {
				pstmt=conn.prepareStatement(sql);
				pstmt.setString(1, u.getUsername());
				pstmt.setString(2, u.getPassword());
				int number=pstmt.executeUpdate();
				System.out.println(number);
				boolean registSuccess=false;
				if(number==1)
					registSuccess=true;
				if(registSuccess)
					return true;
			} catch (SQLException e) {
				e.printStackTrace();
				return false;
			}
			
		}
		return false;
		
	}
	private boolean isExist(User u){
		String sql="select * from user where username=?";
		try {
			pstmt=conn.prepareStatement(sql);
			pstmt.setString(1, u.getUsername());
			rs=pstmt.executeQuery();
			if(rs.next())
				return true;
			else 
				return false;
		} catch (SQLException e) {
			return true;
		}
	}
	public int queryIdByUsername(String username){
		String sql="select userid from user where username=?";
		try{
			pstmt=conn.prepareStatement(sql);
			pstmt.setString(1, username);
			rs=pstmt.executeQuery();
			if(rs.next())
				return rs.getInt("userid");
		}catch(SQLException sqle){
			System.out.println("数据库操作异常");
		}
		return -1;
	}
	public User queryUser(String username,String password){
		User user=null;
		String sql="select * from user where username=? and password=?";
		try {
			pstmt=conn.prepareStatement(sql);
			pstmt.setString(1, username);
			pstmt.setString(2, password);
			rs=pstmt.executeQuery();
			if(rs.next()){
				user=new User();
				user.setUsername(username);
				user.setPassword(password);
			}
		} catch (SQLException e) {
			System.out.println("数据库操作异常");
		}
		
		return user;
	}
}