1.简介 
用户登录模块，指的是根据用户输入的用户名和密码，对用户的身份进行验证等。如果用户没有登录，用户就无法访问其他的一些jsp页面，甚至是action都不能访问。 
二、简单设计及实现 
本程序是基于Java的SSH框架进行的。 
1.数据库设计 

我们应该设计一个用户表，其Userinfo表，对应的SQL语句为（Oracle数据库）：

create table userinfo
(
  id                        varchar2(36) primary key,
  username                 varchar2(50) not null,
  password                 varchar2(50) not null,
  auth_limit               varchar2(10) not null,
  register_time           varchar2(40),
  create_time             varchar2(40),
  remarks                  varchar2(1024)               
);

分别是id，也就是UUID，用户名、密码、权限、注册时间、记录插入数据库的时间、备注等几个字段。

2.使用MyEclipse的Hibernate逆向工具，生成对应的Java Bean和相应的hibernate的xml配置文件Userinfo.hbm.xml 

package edu.njupt.zhb.bean;

/**
 * Userinfo entity. @author MyEclipse Persistence Tools
 */

public class Userinfo implements java.io.Serializable {

  // Fields

  private String id;
  private String username;
  private String password;
  private String authLimit;
  private String registerTime;
  private String createTime;
  private String remarks;

  // Constructors

  /** default constructor */
  public Userinfo() {
  }

  /** minimal constructor */
  public Userinfo(String id, String username, String password,
      String authLimit) {
    this.id = id;
    this.username = username;
    this.password = password;
    this.authLimit = authLimit;
  }

  /** full constructor */
  public Userinfo(String id, String username, String password,
      String authLimit, String registerTime, String createTime,
      String remarks) {
    this.id = id;
    this.username = username;
    this.password = password;
    this.authLimit = authLimit;
    this.registerTime = registerTime;
    this.createTime = createTime;
    this.remarks = remarks;
  }

  // Property accessors

  public String getId() {
    return this.id;
  }

  public void setId(String id) {
    this.id = id;
  }

  public String getUsername() {
    return this.username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return this.password;
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public String getAuthLimit() {
    return this.authLimit;
  }

  public void setAuthLimit(String authLimit) {
    this.authLimit = authLimit;
  }

  public String getRegisterTime() {
    return this.registerTime;
  }

  public void setRegisterTime(String registerTime) {
    this.registerTime = registerTime;
  }

  public String getCreateTime() {
    return this.createTime;
  }

  public void setCreateTime(String createTime) {
    this.createTime = createTime;
  }

  public String getRemarks() {
    return this.remarks;
  }

  public void setRemarks(String remarks) {
    this.remarks = remarks;
  }

}

3.新建一个UserInfoService接口

/*
 * $filename: VideoInfoService.java,v $
 * $Date: 2014-1-2  $
 * Copyright (C) ZhengHaibo, Inc. All rights reserved.
 * This software is Made by Zhenghaibo.
 */
package edu.njupt.zhb.service;

import edu.njupt.zhb.bean.Userinfo;

/*
 *@author: ZhengHaibo  
 *web:     http://blog.csdn.net/nuptboyzhb
 *GitHub   https://github.com/nuptboyzhb
 *mail:    zhb931706659@126.com
 *2014-1-2  Nanjing,njupt,China
 */
public interface UserInfoService {

  String getUserInfoList(int page, int rows);

  String addUser(Userinfo userinfo);

  String deleteUser(String userId);

  String editUser(Userinfo userinfo);

  Userinfo getUserInfoByName(String username);


}

4.新建一个UserInfoServiceImpl类

/*
 * $filename: VideoInfoServiceImpl.java,v $
 * $Date: 2014-1-2  $
 * Copyright (C) ZhengHaibo, Inc. All rights reserved.
 * This software is Made by Zhenghaibo.
 */
package edu.njupt.zhb.service.impl;

import java.util.ArrayList;
import java.util.List;

import net.sf.json.JSONObject;

import edu.njupt.zhb.bean.Userinfo;
import edu.njupt.zhb.dao.BaseDao;
import edu.njupt.zhb.service.UserInfoService;
import edu.njupt.zhb.utils.DataGrid;
import edu.njupt.zhb.utils.Tips;
import edu.njupt.zhb.view.ViewUser;

/*
 *@author: ZhengHaibo  
 *web:     http://blog.csdn.net/nuptboyzhb
 *GitHub   https://github.com/nuptboyzhb
 *mail:    zhb931706659@126.com
 *2014-1-2  Nanjing,njupt,China
 */
public class UserInfoServiceImpl implements UserInfoService{
  private BaseDao<Userinfo> userinfoBaseDao;
  public BaseDao<Userinfo> getUserBaseDao() {
    return userinfoBaseDao;
  }
  public void setUserBaseDao(BaseDao<Userinfo> userinfoBaseDao) {
    this.userinfoBaseDao = userinfoBaseDao;
  }
  @Override
  public String getUserInfoList(int page, int rows) {
    // TODO Auto-generated method stub
    System.out.println("page="+page+",rows="+rows);
    String hql = "from Userinfo";
    try {
      List<Userinfo> list = userinfoBaseDao.find(hql,page,rows);
      List<ViewUser> resultList = new ArrayList<ViewUser>();
      for(Userinfo userinfo:list){
        ViewUser viewUser = new ViewUser();
        viewUser.setBz(userinfo.getRemarks());
        viewUser.setId(userinfo.getId());
        viewUser.setPwd(userinfo.getPassword());
        viewUser.setYhm(userinfo.getUsername());
        viewUser.setYhqx(userinfo.getAuthLimit());
        viewUser.setZcsj(userinfo.getRegisterTime());
        resultList.add(viewUser);
      }
      DataGrid<ViewUser> dataGrid = new DataGrid<ViewUser>();
      dataGrid.setRows(resultList);
      dataGrid.setTotal(userinfoBaseDao.total(hql));
      String result = JSONObject.fromObject(dataGrid).toString();
      return result;
    } catch (Exception e) {
      e.printStackTrace();
      return null;
    }
  }
  
  public String addUser(Userinfo userinfo) {
    // TODO Auto-generated method stub
    Tips tips = new Tips();
    String hql = "from Userinfo where username = '"+userinfo.getUsername()+"'";
    try {
      List<Userinfo> list =  userinfoBaseDao.find(hql);
      if(list!=null&&list.size()>0){
        tips.setMsg("添加失败!用户名已经存在！");
        return JSONObject.fromObject(tips).toString();
      }
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    try {
      userinfoBaseDao.save(userinfo);
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
      tips.setMsg("添加失败");
      return JSONObject.fromObject(tips).toString();
    }
    tips.setMsg("添加成功");
    return JSONObject.fromObject(tips).toString();
  }
  public String deleteUser(String userid) {
    // TODO Auto-generated method stub
    Tips tips = new Tips();
    try {
      userinfoBaseDao.executeHql("delete from Userinfo where id = '"+userid+"'");
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
      tips.setMsg("删除失败");