Servlet生成验证码

package com.yonyou.webapp.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.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 javax.servlet.http.HttpSession;

/**
 * Servlet implementation class CodeUtil
 */
@WebServlet("/codeutil")
public class CodeUtil extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public CodeUtil() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // System.out.println("哈哈哈");
        response.setContentType("image/jpeg");
        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 在内存中创建图像
        int width = 90;
        int height = 35;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        Graphics g = image.getGraphics();
        // 随机类
        Random random = new Random();
        // 设定背景
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);
        // 设定字体
        g.setFont(new Font("Times New Roman", Font.PLAIN, 30));
        // 随机产生干扰线
        g.setColor(getRandColor(160, 200));
        for (int i = 0; i < 100; 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);
        }
        // 随机产生4位验证码
        String[] codes = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H",
                "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "a", "b", "c",
                "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x",
                "y", "z" };
        String code = "";
        for (int i = 0; i < 4; i++) {
            String str = codes[random.nextInt(codes.length)];
            code += str;
            // 将认证码显示到图象中
            g.setColor(new Color(50 + random.nextInt(110), 20 + random.nextInt(110), 30 + 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(str, 18 * i + 13, 27); // 文字间距*i+距离左边距，上边距
        }
        HttpSession session = request.getSession();
        // 将认证码存入SESSION
        session.setAttribute("code", code);
        // 图象生效
        g.dispose();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", response.getOutputStream());
        // 加上下面代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has
        // already been called ..........等异常
        response.getOutputStream().flush();
        response.getOutputStream().close();
        response.flushBuffer();
    }

    // 获取随机颜色
    private Color getRandColor(int fc, int bc) {
        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);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

后台验证

package com.yonyou.webapp.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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;

/**
 * Servlet implementation class CheckCodeServlet
 */
@WebServlet("/checkcode")
public class CheckCodeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public CheckCodeServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        String inCode = request.getParameter("input_code");
        HttpSession session = request.getSession();
        int result = 0;
        if(session.getAttribute("code").toString().equalsIgnoreCase(inCode)){
            result = 1;
        } 
        response.setCharacterEncoding("utf-8");
        response.setContentType("text");
        PrintWriter out = response.getWriter();
        out.println(result);
        out.flush();
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

前端Ajax验证

<script type="text/javascript">
    $(function(){
        
        $("#btn_login").click(function(){
            //异步请求(Ajax)
            $.post("checkcode",{"input_code":$("#code").val()},function(rlt){
                //alert("|"+rlt.trim()+"|");
                if(rlt==1){
                    $("#login_form").submit();
                }else{
                    alert("验证码输入错误!");
                }
            })
        });
        
    });
</script>