添加验证码

第一步：web.xml添加servlet配置

<servlet>
    <servlet-name>ValidCode</servlet-name>
    <servlet-class>com.xxx.core.web.servlet.ValidCode</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>ValidCode</servlet-name>
    <url-pattern>/servlet/ValidCode</url-pattern>
</servlet-mapping>

 

第二步：编写java类 ValidCode.java(继承HttpServlet)

 

package com.xxx.core.web.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.jimi.core.Jimi;
import com.sun.jimi.core.JimiException;

/**
 * 功能： 产生验证码。<br>
 * 从session中获取验证码。<br>
 * 获取验证码方法如下：<br>
 * String code=session.getAttribute(ValidCode.SessionName_Randcode);<br>
 * 需要在web.xml中进行配置。<br>
 **/

public class ValidCode extends HttpServlet {

    private static final long serialVersionUID = 1L;
    public static String SessionName_Randcode = "randcode";

    public ValidCode() {
        super();
    }

    public void destroy() {
        super.destroy();
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");
        // 在内存中创建图象
        int width = 60, height = 20;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        Graphics g = image.getGraphics();
        // 生成随机类
        Random random = new Random();
        // 设定背景色
        g.setColor(getRandColor(155, 254));
        // g.setColor(new Color(255,255,255));
        g.fillRect(0, 0, width, height);
        // 设定字体
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
        // 画边框
        // g.setColor(new Color());
        // g.drawRect(0,0,width-1,height-1);
        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
        g.setColor(getRandColor(160, 220));
        for (int i = 0; i < 155; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int xl = random.nextInt(12);
            int yl = random.nextInt(12);
            g.drawLine(x, y, x + xl, y + yl);
        }
        // 取随机产生的认证码(4位数字)
        String sRand = "";
        for (int i = 0; i < 4; i++) {
            String rand = String.valueOf(random.nextInt(10));
            sRand += rand;
            // 将认证码显示到图象中
            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
            g.drawString(rand, 13 * i + 6, 16);
        }
        // 将认证码存入SESSION
        request.getSession().setAttribute(SessionName_Randcode, sRand);
        // 图象生效
        g.dispose();
        // 输出图象到页面

        ServletOutputStream os = response.getOutputStream();
        // ImageIO.write(image, "JPEG", os);
        try {
            Jimi.putImage("image/jpeg", image, os);
        } catch (JimiException e) {
            e.printStackTrace();
        }
        os.flush();
        os.close();
        os = null;
        response.flushBuffer();
    }

    private Color getRandColor(int fc, int bc) {
        // 给定范围获得随机颜色
        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);
    }

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

    public void init() throws ServletException {
        // Put your code here
    }
}

 

第三步，前端页面添加相关控件

<div class="yzmBody">
    <input id="yzm" name="validCode" class="floatLeft" placeholder="请输入验证码" /> <img src="${ctx}/servlet/ValidCode" class="floatLeftTwo" id="validImg" />
</div>

<label class="inline"> <a class="" type="button" onclick="reload()">刷新验证码</a>
</label>

<c:set var="ctx" value="${pageContext.request.contextPath}" />

 

js代码

//刷新验证码

function reload() {
    var url = "${ctx}/servlet/ValidCode?rand=" + new Date().getTime();
    document.getElementById("validImg").src = url;
}

 

后台代码判断

        String validCode = (String) request.getSession().getAttribute(ValidCode.SessionName_Randcode);
        String code = request.getParameter("validCode");
        if (validCode == null || StringUtils.isEmpty(code) || !validCode.equals(code)) {
        request.getSession().setAttribute(WebAttributes.AUTHENTICATION_EXCEPTION, "验证码不正确！");
        error = true;
        throw new AccessDeniedException("验证码不正确");