如何用DAO设计模式实现长尾词的登录、注册与查询功能？

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javapackage com.dao;

import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.util.ArrayList;import java.util.List;

import com.db.DB;import com.user.Users;

public class UserDao implements UserI { DB db;}

DAO

package com.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.db.DB; import com.user.Users; public class UserDao implements UserI { DB db = new DB(); Connection conn; // 登录 public boolean loginConn(Users user) throws Exception { // TODO Auto-generated method stub conn = db.getConn(); String sql = "select * from users_table where db_user = ? and db_password = ?"; PreparedStatement ps = conn.prepareStatement(sql); ps.setString(1, user.getDb_user()); ps.setString(2, user.getDb_password()); ResultSet rs = ps.executeQuery(); boolean flag = rs.next(); rs.close(); ps.close(); db.closeConn(); return flag; } // 注册 public int insertData(Users user) throws Exception { // TODO Auto-generated method stub conn = db.getConn(); String sql = "insert into users_table(db_user,db_password) VALUES (?,?);"; PreparedStatement ps = conn.prepareStatement(sql); ps.setString(1, user.getDb_user()); ps.setString(2, user.getDb_password()); int a = ps.executeUpdate(); ps.close(); db.closeConn(); return a; } // 查询 public List getAllData() throws Exception { // TODO Auto-generated method stub conn = db.getConn(); String sql = "select * from users_table"; PreparedStatement ps = conn.prepareStatement(sql); ResultSet rs = ps.executeQuery(); List list = new ArrayList(); while (rs.next()) { Users u = new Users(); u.setDb_id(rs.getInt(1)); u.setDb_user(rs.getString(2)); u.setDb_password(rs.getString(3)); list.add(u); } rs.close(); ps.close(); db.closeConn(); return list; } public static void main(String[] args) { UserI i = new UserDao(); Users u = new Users(); // 测试登录 u.setDb_user("D_nice"); u.setDb_password("487561"); try { boolean flag = i.loginConn(u); //返回true登录成功 返回false登录失败 System.out.println("登录" + flag); } catch (Exception e) { e.printStackTrace(); } //测试注册 try { Users user = new Users(); user.setDb_user("first"); user.setDb_password("147258"); int a = i.insertData(user); if(a>0){ System.out.println("注册成功"); }else{ System.out.println("注册失败"); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } //测试查询 try { List list = i.getAllData(); for (int a = 0; a < list.size(); a++) { Users user = new Users(); user = list.get(a); System.out.println("查询结果如下："); System.out.println("ID:" + user.getDb_id() + "USER:" + user.getDb_user() + "PASSWORD:" + user.getDb_password()); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } 运行结果.png 数据库.png