验证码
1.本质:是图片
2. 目的:防止恶意表单注册,验证码还是很有必要的
使用验证码的方式:
3. 提前存储在内存中,使用时随机选取
4. 使用时,由系统随机生成
自动生成一个随机验证码图片:
package cn.itcast.web.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width =