java web-简单的验证码登录验证
小结思路：编写login.jsp，登录页面展示，并且提交用户填的信息，调用资源Loginservlet进行判断，由于验证码每次刷新都是调用checkServlet进行随机创建，所以必须在一创建就传入session内部进行保存，共享资源，之后来到loginServlet里的逻辑判断，获取session下的验证码，先判断验证码，之后再判断数据库内的用户信息是否一致，这里需要额外完善一个user类和userDao类，涉及jdbc，jdbctemplate等技术，编写utils等下次再完善。之后验证码错误或者用户密码错误，进行内部资源跳转。而成功的话，把用户信息保存到session里面，然后只能重定向到web下面的一个success.jsp，显示用户登录成功。（这里有个问题，能不能直接内部资源跳转，本实验最后验证一下）
说明：验证码部分checkCode，采用直接画个框显示，然后随机划线0.0，而且注意在获取验证判断后里面把这个session里面对应的值删掉，反之成功登陆后返回页面（不刷新），可以不断登陆，浪费服务器资源！
样例：
附上源码：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>login</title>
<script>
window.onload = function () {
document.getElementById("img").onclick = function () {
this.src = "/jsp_learn/checkCodeServlet?time="+new Date().getTime();
}
}
</script>
</head>
<BODY>
<form action="/jsp_learn/loginServlet" method="post">
<table>
<tr>
<td>用户名</td>
<td><input type="text" name="username"></td>
</tr>
<tr>
<td>密码</td>
<td><input type="text" name="password"></td>
</tr>
<tr>
<td colspan="2"><img id="img" src="/jsp_learn/checkCodeServlet"></td>
</tr>
<tr>
<td>验证码</td>
<td><input type="text" name="checkCode"></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="登录"></td>
</tr>
</table>
<div><%=request.getAttribute("cc_error")%></div>
<div><%=request.getAttribute("login_error")%></div>
</form>
</BODY>
</html>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<BODY>
<h1><%=request.getSession().getAttribute("user")%>欢迎你，</h1>
</BODY>
</html>
package 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 = 100;
int height = 50;
//1.创建一对象，在内存中图片(验证码图片对象)
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//2.美化图片
//2.1 填充背景色
Graphics g = image.getGraphics();//画笔对象
g.setColor(Color.PINK);//设置画笔颜色
g.fillRect(0,0,width,height);
//2.2画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width - 1,height - 1);
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
//生成随机角标
Random ran = new Random();
StringBuilder sb = new StringBuilder();
for (int i = 1; i <= 4; i++) {
int index = ran.nextInt(str.length());
//获取字符
char ch = str.charAt(index);//随机字符
sb.append(ch);
//2.3写验证码
g.drawString(ch+"",width/5*i,height/2);
}
String checkCode_session = sb.toString();
//将验证码存入session
request.getSession().setAttribute("checkCode_session",checkCode_session);
//2.4画干扰线
g.setColor(Color.GREEN);
//随机生成坐标点
for (int i = 0; i < 10; i++) {
int x1 = ran.nextInt(width);
int x2 = ran.nextInt(width);
int y1 = ran.nextInt(height);
int y2 = ran.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
//3.将图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
package servlet;
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 javax.servlet.http.HttpSession;
import java.io.IOException;
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
//获取参数
String username = request.getParameter("username");
String password = request.getParameter("password");
String checkCode = request.getParameter("checkCode");
System.out.println(username);
//2.获取生成的验证码
HttpSession session = request.getSession();
String checkCode_session = (String)session.getAttribute("checkCode_session");
session.removeAttribute("checkCode_session");
//3.判断验证码是否正确
if(checkCode_session!=null &&checkCode_session.equalsIgnoreCase(checkCode)){
//验证码正确
if("zxl".equals(username) && "123".equals(password)){//升级：需要Beanutil封装user，并且调用(含jdbc的util等)userDao进行判断
//登录成功
//存储信息，用户信息
//由于是重定向，两次请求，必须将信息存到session里面
session.setAttribute("user", username);
//重定向，输出信息，success.jsp ,
response.sendRedirect(request.getContextPath()+"/success.jsp");
}
else {
//登录失败
request.setAttribute("login_error", "用户名密码错误");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
}
else{
//验证码错误
request.setAttribute("cc_error", "验证码错误");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
事实证明这里用内部资源跳转也可以，最重要的是验证码的内部获取需要用session，因为都是两个servlet里面的
request.setAttribute("user", username);
request.getRequestDispatcher("/success.jsp").forward(request, response);
