Servlet实现登录带有验证码验证案例

1.用户实体类User.java

public class User implements Serializable {
    private int uid;//用户id
    private String username;//用户名，账号
    private String password;//密码
    private String name;//真实姓名
    private String birthday;//出生日期
    private String sex;//男或女
    private String telephone;//手机号
    private String email;//邮箱
    private String status;//激活状态，Y代表激活，N代表未激活
    private String code;//激活码（要求唯一）
    ...
    //省略getter setter 有参无参构造 ToString方法
}

2.抽取出来的BaseServlet.java以便自己的Servlet更加简洁

public class BaseServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //System.out.println("baseServlet的service方法被执行了...");
        //完成方法分发
        //1.获取请求路径
        String uri = req.getRequestURI(); //   /travel/user/add
        System.out.println("请求uri:"+uri);//  /travel/user/add
        //2.获取方法名称
        String methodName = uri.substring(uri.lastIndexOf('/') + 1);
        System.out.println("方法名称："+methodName);
        //3.获取方法对象Method
        //谁调用我？我代表谁
        System.out.println(this);//UserServlet的对象cn.itcast.travel.web.servlet.UserServlet@4903d97e
        try {
            //获取方法
            Method method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
            //4.执行方法
            //暴力反射
            //method.setAccessible(true);
            method.invoke(this,req,resp);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    /**
     * 直接将传入的对象序列化为json，并且写回客户端
     * @param obj
     */
    public void writeValue(Object obj,HttpServletResponse response) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        response.setContentType("application/json;charset=utf-8");
        mapper.writeValue(response.getOutputStream(),obj);
    }

    /**
     * 将传入的对象序列化为json，返回
     * @param obj
     * @return
     */
    public String writeValueAsString(Object obj) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        return mapper.writeValueAsString(obj);
    }
}

3.UserServlet.java

@WebServlet("/user/*") 
public class UserServlet extends BaseServlet {

    //声明UserService业务对象
    private UserService service = new UserServiceImpl(); 
    /**
     * 登录功能
     * @param request
     * @param response
     * @throws ServletException
     * @throws IOException
     */
    public void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //所有的开始首先校验前端的验证码
        //验证校验
        String check = request.getParameter("check");
        //从sesion中获取验证码
        HttpSession session = request.getSession();
        String checkcode_server = (String) session.getAttribute("CHECKCODE_SERVER");
        session.removeAttribute("CHECKCODE_SERVER");//为了保证验证码只能使用一次
        //比较
        if(checkcode_server == null || !checkcode_server.equalsIgnoreCase(check)){
            //验证码错误
            ResultInfo info = new ResultInfo();
            //注册失败
            info.setFlag(false);
            info.setErrorMsg("验证码错误");
            //将info对象序列化为json
            ObjectMapper mapper = new ObjectMapper();
            String json = mapper.writeValueAsString(info);
            response.setContentType("application/json;charset=utf-8");
            response.getWriter().write(json);
            return;
        }
        
        //1.获取用户名和密码数据
        Map<String, String[]> map = request.getParameterMap();
        //2.封装User对象
        User user = new User();
        try {
            BeanUtils.populate(user,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //3.调用Service查询
       // UserService service = new UserServiceImpl();
        User u  = service.login(user);

        ResultInfo info = new ResultInfo();

        //4.判断用户对象是否为null
        if(u == null){
            //用户名密码或错误
            info.setFlag(false);
            info.setErrorMsg("用户名密码或错误");
        }
        //5.判断用户是否激活
        if(u != null && !"Y".equals(u.getStatus())){
            //用户尚未激活
            info.setFlag(false);
            info.setErrorMsg("您尚未激活，请激活");
        }
        //6.判断登录成功
        if(u != null && "Y".equals(u.getStatus())){
            request.getSession().setAttribute("user",u);//登录成功标记
            //登录成功
            info.setFlag(true);
        }

        //响应数据
        ObjectMapper mapper = new ObjectMapper();

        response.setContentType("application/json;charset=utf-8");
        mapper.writeValue(response.getOutputStream(),info);
    }
}

4.UserService接口

public interface UserService {
    /**
     * 注册用户
     * @param user
     * @return
     */
    boolean regist(User user);

    boolean active(String code);

    User login(User user);
}

5.UserServiceImpl实现类

public class UserServiceImpl implements UserService {
    private UserDao userDao = new UserDaoImpl();
    /**
     * 登录方法
     * @param user
     * @return
     */
    @Override
    public User login(User user) {
        return userDao.findByUsernameAndPassword(user.getUsername(),user.getPassword());
    }
}

6.Dao层接口```java

public interface UserDao { User findByUsernameAndPassword(String username, String password); }

### 7.UserDaoImpl实现类
```java
public class UserDaoImpl implements UserDao {

    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 根据用户名和密码查询的方法
     * @param username
     * @param password
     * @return
     */
    @Override
    public User findByUsernameAndPassword(String username, String password) {
        User user = null;
        try {
            //1.定义sql
            String sql = "select * from tab_user where username = ? and password = ?";
            //2.执行sql
            user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class), username,password);
        } catch (Exception e) {

        }

        return user;
    }
}

7.JDBCUtils.java工具类

/*
  1. 声明静态数据源成员变量
  2. 创建连接池对象
  3. 定义公有的得到数据源的方法
  4. 定义得到连接对象的方法
  5. 定义关闭资源的方法
 */
public class JDBCUtils {
  // 1. 声明静态数据源成员变量
  private static DataSource ds;

  // 2. 创建连接池对象
  static {
    // 加载配置文件中的数据
    InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
    Properties pp = new Properties();
    try {
      pp.load(is);
      // 创建连接池，使用配置文件中的参数
      ds = DruidDataSourceFactory.createDataSource(pp);
    } catch (IOException e) {
      e.printStackTrace();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  // 3. 定义公有的得到数据源的方法
  public static DataSource getDataSource() {
    return ds;
  }

  // 4. 定义得到连接对象的方法
  public static Connection getConnection() throws SQLException {
    return ds.getConnection();
  }

  // 5.定义关闭资源的方法
  public static void close(Connection conn, Statement stmt, ResultSet rs) {
    if (rs != null) {
      try {
        rs.close();
      } catch (SQLException e) {}
    }

    if (stmt != null) {
      try {
        stmt.close();
      } catch (SQLException e) {}
    }

    if (conn != null) {
      try {
        conn.close();
      } catch (SQLException e) {}
    }
  }

  // 6.重载关闭方法
  public static void close(Connection conn, Statement stmt) {
    close(conn, stmt, null);
  }
}

7.验证码CheckCodeServlet.java

/**
 * 验证码
 */
@WebServlet("/checkCode")
public class CheckCodeServlet extends HttpServlet {
  public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
    
    //服务器通知浏览器不要缓存
    response.setHeader("pragma","no-cache");
    response.setHeader("cache-control","no-cache");
    response.setHeader("expires","0");
    
    //在内存中创建一个长80，宽30的图片，默认黑色背景
    //参数一：长
    //参数二：宽
    //参数三：颜色
    int width = 80;
    int height = 30;
    BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
    
    //获取画笔
    Graphics g = image.getGraphics();
    //设置画笔颜色为灰色
    g.setColor(Color.GRAY);
    //填充图片
    g.fillRect(0,0, width,height);
    
    //产生4个随机验证码，12Ey
    String checkCode = getCheckCode();
    //将验证码放入HttpSession中
    request.getSession().setAttribute("CHECKCODE_SERVER",checkCode);
    
    //设置画笔颜色为黄色
    g.setColor(Color.YELLOW);
    //设置字体的小大
    g.setFont(new Font("黑体",Font.BOLD,24));
    //向图片上写入验证码
    g.drawString(checkCode,15,25);
    
    //将内存中的图片输出到浏览器
    //参数一：图片对象
    //参数二：图片的格式，如PNG,JPG,GIF
    //参数三：图片输出到哪里去
    ImageIO.write(image,"PNG",response.getOutputStream());
  }
  /**
   * 产生4位随机字符串 
   */
  private String getCheckCode() {
    String base = "0123456789ABCDEFGabcdefg";
    int size = base.length();
    Random r = new Random();
    StringBuffer sb = new StringBuffer();
    for(int i=1;i<=4;i++){
      //产生0到size-1的随机值
      int index = r.nextInt(size);
      //在base字符串中获取下标为index的字符
      char c = base.charAt(index);
      //将c放入到StringBuffer中去
      sb.append(c);
    }
    return sb.toString();
  }
  public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doGet(request,response);
  }
}

8.HTML中的验证码，登录各个参数不做展示

//引入验证码
<img src="checkCode" height="32px" alt="" onclick="changeCheckCode(this)">
  <script type="text/javascript">
    //图片点击事件
    function changeCheckCode(img) {
    img.src="checkCode?"+new Date().getTime();
         }
  </script>