从零玩转JavaWeb系列7web服务器-----用户登录界面二维码的制作

1.用eclipse工具新建一个Dynamic Web Project工程如下：

2.在Java Resources的src目录下新建一个包，包名称为com.it666.code

3.在com.it666.code包下创建2个Servlet，名字分别为CheckCodeServelt、RegistServlet

CheckCodeServelt代码：

package com.it666.code;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

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;

@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    // 集合中保存所有成语
    private List<String> words = new ArrayList<String>();

    @Override
    public void init() throws ServletException {
        // 初始化阶段，读取new_words.txt
        // web工程中读取 文件,必须使用绝对磁盘路径
        String path = getServletContext().getRealPath("/WEB-INF/words.txt");
        try {
            BufferedReader reader = new BufferedReader(new FileReader(path));
            String line;
            //把读的成语全部添加到一个集合当中
            while ((line = reader.readLine()) != null) {
                words.add(line);
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        int width = 120;
        int height = 30;
        // 步骤一 绘制一张内存中图片
        BufferedImage bufferedImage = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        // 步骤二 图片绘制背景颜色 ---通过绘图对象
        Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔
        // 绘制任何图形之前 都必须指定一个颜色
        graphics.setColor(getRandColor(200, 250));
        graphics.fillRect(0, 0, width, height);
        // 步骤三 绘制边框
        graphics.setColor(Color.WHITE);
        graphics.drawRect(0, 0, width - 1, height - 1);
        // 步骤四 四个随机数字
        Graphics2D graphics2d = (Graphics2D) graphics;
        // 设置输出字体
        graphics2d.setFont(new Font("宋体", Font.BOLD, 18));
        Random random = new Random();// 生成随机数
        int index = random.nextInt(words.size());
        String word = words.get(index);// 获得成语
        System.out.println(word);
        // 定义x坐标
        int x = 10;
        for (int i = 0; i < word.length(); i++) {
            // 随机颜色
            graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random
                    .nextInt(110), 20 + random.nextInt(110)));
            // 旋转 -30 --- 30度
            int jiaodu = random.nextInt(60) - 30;
            // 换算弧度
            double theta = jiaodu * Math.PI / 180;

            // 获得字母数字
            char c = word.charAt(i);

            // 将c 输出到图片
            graphics2d.rotate(theta, x, 20);
            graphics2d.drawString(String.valueOf(c), x, 20);
            graphics2d.rotate(-theta, x, 20);
            x += 30;
        }

        // 将验证码内容保存session(企业开发当中用)
        //request.getSession().setAttribute("checkcode_session", word);
        //把生成的验证码存放到全局域对象当中（一般不会用这种方法）
        this.getServletContext().setAttribute("checkCode", word);
        // 步骤五 绘制干扰线
        graphics.setColor(getRandColor(160, 200));
        int x1;
        int x2;
        int y1;
        int y2;
        for (int i = 0; i < 30; i++) {
            x1 = random.nextInt(width);
            x2 = random.nextInt(12);
            y1 = random.nextInt(height);
            y2 = random.nextInt(12);
            graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
        }
        // 将上面图片输出到浏览器 ImageIO
        graphics.dispose();// 释放资源
        //将图片写到response.getOutputStream()中
        ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

    /**
     * 取其某一范围的color
     *
     * @param fc
     *            int 范围参数1
     * @param bc
     *            int 范围参数2
     * @return Color
     */
    private Color getRandColor(int fc, int bc) {
        // 取其随机颜色
        Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

}

RegistServlet代码如下：

package com.it666.code;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/RegistServelt")
public class RegistServelt extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //接收请求参数的内容
        String code = request.getParameter("code");
        System.out.println(code);

        //将请求的参数内容由ISO8859-1转码成UTF-8
        byte[] bytes = code.getBytes("ISO8859-1");
        code = new String(bytes,"UTF-8");
        System.out.println("code="+code);

        //获取验证码内容
        String name = (String)this.getServletContext().getAttribute("checkCode");
        System.out.println("name="+name);

        //设置缓冲区当中使用的编码
        //response.setCharacterEncoding("UTF-8");

        //设置缓冲区当中使用的编码、告诉浏览器要用什么字符集来接收响应
        response.setContentType("text/html;charset=UTF-8");

        //进行匹配并且输出匹配结果
        if(name.equals(code)) {
            response.getWriter().write("验证码 正确");
        }else {
            response.getWriter().write("验证码 错误");
            response.setHeader("refresh", "3;url=/26-Servlet/code.html");
        }

    }

}

4.在WebContent文件夹的WEB-INF文件夹下面创建web.xml、words.txt。

web.xml代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" metadata-complete="false" version="3.0">
  <absolute-ordering/>
  <display-name>web</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

words.txt文件主要用于放验证码的文字。如下：

5.在WebContent文件夹下只创建code.html文件（其他文件不用创建）

code.html代码：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>code</title>

<script type="text/javascript">
    function chang(obj) {
        obj.src = "/26-Servlet/CheckCodeServlet?time=" + new Date().getTime();
    }
</script>

</head>
<body>
    <form action="/26-Servlet/RegistServelt">
        <img src="/26-Servlet/CheckCodeServlet" onclick="chang(this)"> <br />
        <input type="text" placeholder="请输入验证码..." name ="code"> <br />
        <input type="submit"  value="注册">
    </form>

</body>
</html>

6.在code.html文件下单机运行即可

以下为eclipse工具测试结果：

1.匹配正确实例：

2.匹配错误实例：

原文地址：https://www.cnblogs.com/zhou-shi-yuan-ISO8859-1/p/9526255.html