在登录界面中使用图片验证码, 对于现在的web应用到处可见.
话不多说, 开始写代码了!
首先, 新建一个JSP, 表示登录界面:
login3.jsp文件:
<%--
User: menglanyingfei
Date: 2018/1/12
Time: 16:16
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>登录界面</title>
</head>
<body>
<%
// 获取浏览器发送过来的cookie, 获取用户信息
Cookie[] cookies = request.getCookies();
String username = "";
if (cookies != null) {
for (Cookie cookie : cookies) {
if ("username".equals(cookie.getName())) {
username = cookie.getValue();
}
}
}
%>
<font color="red">${requestScope.message}</font>
<form action="/day_1_12/LoginServlet3" method="post">
用户名:<input type="text" name="username" value="<%= username%>"><font color="red">${requestScope.error}</font>
<br>
密码:<input type="password" name="password">
<br>
验证码:<input type="text" name="image">
<img src="/day_1_12/VerifyCodeServlet">
<input type="button" value="看不清? 换一张." id="btn"><font color="red">${requestScope.imageMess}</font>
<br>
<input type="submit" value="登录">
</form>
<script type="text/javascript">
document.getElementById("btn").onclick = function () {
// 获取img元素
// 为了让浏览器发送请求到servlet, 所以一定要改变src
document.getElementsByTagName("img")[0].src =
"/day_1_12/VerifyCodeServlet?time=" + new Date().getTime();
};
</script>
</body>
</html>
界面就是这样, 当然, 你肯定现在出来不了这个效果! 没事, 接着往下看吧!
登录界面.png
然后, 新建一个Servlet:
VerifyCodeServlet.java文件, 因为这里配置了@WebServlet注解, 所以无需在web.xml中配置!
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.image.BufferedImage;
import java.io.IOException;
/**
* 用来生成图片验证码
* Created by menglanyingfei on 2018/1/12.
*/
@WebServlet(name = "VerifyCodeServlet", value = "/VerifyCodeServlet")
public class VerifyCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//创建对象
VerifyCode vc = new VerifyCode();
//获取图片对象
BufferedImage bi = vc.getImage();
//获得图片的文本内容
String text = vc.getText();
// 将系统生成的文本内容保存到session中
request.getSession().setAttribute("text", text);
//向浏览器输出图片
vc.output(bi, response.getOutputStream());
}
}
在同一包下, 新建一个Java文件VerifyCode.java(具体的代码意思, 可以看注释, 已经写得非常清楚了!):
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
public class VerifyCode {
private int w = 70;
private int h = 35;
private Random r = new Random();
// {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}
private String[] fontNames = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"};
// 可选字符
private String codes = "0123456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
// 背景色
private Color bgColor = new Color(255, 255, 255);
// 验证码上的文本
private String text ;
// 生成随机的颜色
private Color randomColor () {
int red = r.nextInt(150);
int green = r.nextInt(150);
int blue = r.nextInt(150);
return new Color(red, green, blue);
}
// 生成随机的字体
private Font randomFont () {
int index = r.nextInt(fontNames.length);
String fontName = fontNames[index];//生成随机的字体名称
int style = r.nextInt(4);//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+斜体)
int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28
return new Font(fontName, style, size);
}
// 画干扰线
private void drawLine (BufferedImage image) {
int num = 3;//一共画3条
Graphics2D g2 = (Graphics2D)image.getGraphics();
for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值
int x1 = r.nextInt(w);
int y1 = r.nextInt(h);
int x2 = r.nextInt(w);
int y2 = r.nextInt(h);
g2.setStroke(new BasicStroke(1.5F));
g2.setColor(Color.BLUE); //干扰线是蓝色
g2.drawLine(x1, y1, x2, y2);//画线
}
}
// 随机生成一个字符
private char randomChar () {
int index = r.nextInt(codes.length());
return codes.charAt(index);
}
// 创建BufferedImage
private BufferedImage createImage () {
BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = (Graphics2D)image.getGraphics();
g2.setColor(this.bgColor);
g2.fillRect(0, 0, w, h);
return image;
}
// 调用这个方法得到验证码
public BufferedImage getImage () {
BufferedImage image = createImage();//创建图片缓冲区
Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境
StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本
// 向图片中画4个字符
for(int i = 0; i < 4; i++) {//循环四次，每次生成一个字符
String s = randomChar() + "";//随机生成一个字母
sb.append(s); //把字母添加到sb中
float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标
g2.setFont(randomFont()); //设置随机字体
g2.setColor(randomColor()); //设置随机颜色
g2.drawString(s, x, h-5); //画图
}
this.text = sb.toString(); //把生成的字符串赋给了this.text
drawLine(image); //添加干扰线
return image;
}
// 返回验证码图片上的文本
public String getText () {
return text;
}
// 保存图片到指定的输出流
public static void output (BufferedImage image, OutputStream out)
throws IOException {
ImageIO.write(image, "JPEG", out);
}
}
处理登录逻辑的Servlet(LoginServlet3.java):
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* Created by menglanyingfei on 2018/1/12.
*/
@WebServlet(name = "LoginServlet3", value = "/LoginServlet3")
public class LoginServlet3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 编码
request.setCharacterEncoding("utf-8");
// 获取请求参数
/*
拿到页面传过来的手动输入的验证码, 该验证码要和生成图片上的
文本验证码比较, 如果相同, 验证码输入成功!
*/
String imageText = request.getParameter("image");
// 图片的验证码
String text = (String) request.getSession().getAttribute("text");
if (!text.equalsIgnoreCase(imageText)) {
request.setAttribute("imageMess", "验证码输入错误!");
request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
}
// 获取用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
if ("haha".equals(username) && "123".equals(password)) {
// 将用户信息保存到session中
request.getSession().setAttribute("username", username);
// 使用cookie实现回写用户名
Cookie cookie = new Cookie("username", username);
cookie.setMaxAge(60 * 60);
// 通过响应头发送cookie
response.addCookie(cookie);
// 重定向登录成功界面
response.sendRedirect(request.getContextPath() + "/jsp/success2.jsp");
} else {
request.setAttribute("error", "用户名或密码错误!");
request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
登录成功后的界面:(success2.jsp)
<%--
User: menglanyingfei
Date: 2018/1/12
Time: 16:44
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>成功登录</title>
</head>
<body>
<%
// 获取用户信息
String username = (String) session.getAttribute("username");
if (username == null) {
// 保存错误信息到request中, 然后转发到login3.jsp中, 提醒登录
request.setAttribute("message", "请登录!");
// 转发到登录页面
request.getRequestDispatcher("/jsp/login3.jsp").forward(request, response);
}
%>
<h2>欢迎登录:${sessionScope.username}!!!</h2>
</body>
</html>
最后, 演示登录:
因为, 用户名haha和密码123已经写死在代码里了!
登录.png
成功.png
完整代码地址
https://github.com/menglanyingfei/Java/tree/master/JavaWebTrain/day_1_12
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