案例需求
1. 在登录页面用户登录的时候要查看到验证码，如图所示：
2. 在生成页面验证码图片的同时，使用session存储验证码
3. 在处理用户登录请求的时候，首先校验验证码
4. 校验通过才能执行登录操作
案例分析
代码实现：
1.页面代码
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2. 配置验证码servlet
@WebServlet(name = "CheckcodeServlet",urlPatterns = "/checkcode")
public class CheckcodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 创建画布
int width = 120;
int height = 40;
BufferedImage bufferedImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 获得画笔
Graphics g = bufferedImage.getGraphics();
// 填充背景颜色
g.setColor(Color.white);
g.fillRect(0, 0, width, height);
// 绘制边框
g.setColor(Color.red);
g.drawRect(0, 0, width - 1, height - 1);
// 生成随机字符3. 登录servlet
// 准备数据
String data =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
// 准备随机对象
Random r = new Random();
// 声明一个变量 保存验证码
String code = "";
// 书写4个随机字符
for (int i = 0; i < 4; i++) {
// 设置字体
g.setFont(new Font("宋体", Font.BOLD, 28));
// 设置随机颜色
g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));
String str = data.charAt(r.nextInt(data.length())) + "";
g.drawString(str, 10 + i * 28, 30);
// 将新的字符 保存到验证码中
code = code + str;
}
// 绘制干扰线
for (int i = 0; i < 6; i++) {
// 设置随机颜色
g.setColor(new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)));
g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width),
r.nextInt(height));
}
// 将验证码 打印到控制台
System.out.println(code);
// 将验证码放到session中
request.getSession().setAttribute("code_session", code);
// 将画布显示在浏览器中
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3. 登录servlet
@WebServlet(name = "LoginServlet",urlPatterns = "/login")
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {4. dao：
//用户请求中的验证码获取
String code = request.getParameter("code");
//获取session中保存的验证码
String code_session =
(String)request.getSession().getAttribute("code_session");
//与session中保存的验证码进行校验
if(!code_session.equalsIgnoreCase(code)){
//验证码错误，告诉用户，页面提示
request.setAttribute("msg","验证码错误");
request.getRequestDispatcher("/login.jsp").forward(request,response);
return;
}
//验证码正确，登录逻辑执行
//获取用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
//调用Service方法，登录用户
UserDao userDao = new UserDao();
User loginUser = userDao.login(username,password);
if(loginUser == null){
request.setAttribute("msg","用户名或则密码错误");
request.getRequestDispatcher("/login.jsp").forward(request,response);
return;
}else{
//登陆成功，跳转主页
response.sendRedirect(request.getContextPath());
return;
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
4. dao：
public class UserDao {
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
/**
* 查询用户名和密码是否匹配的方法
*/
@Override
public User login(String username, String password) {
String sql = "select * from user where username = ? and password = ?";
try {
User query = template.queryForObject(sql, new
BeanPropertyRowMapper<User>(User.class), username,password);
return query;
}catch (Exception e){
e.printStackTrace();
return null;
}
}
}
session的与cookie的区别
