java 生成 验证码

生成验证码的思路：在后台生成一个四位数的随机数，将其放到session里面（验证时用），用这个随机数生成一张带干扰的内存图片（如何干扰，看下面的代码），将图片输出到response的输出流中，在页面显示出来即可

 

创建一个web工程，new一个servlet,web.xml配置如下：

<servlet>
    <description></description>
    <display-name>Image</display-name>
    <servlet-name>Image</servlet-name>
    <servlet-class>org.test.servlet.Image</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Image</servlet-name>
    <url-pattern>/Image</url-pattern>
  </servlet-mapping>

 servlet如下：

 

package org.test.servlet;
 import java.io.*;
    import java.net.*;
    import javax.servlet.*;
    import javax.servlet.http.*;
    import java.awt.*;
    import java.awt.image.*;
    import java.util.*;
    import javax.imageio.*;
    /**
     *
     * @author http://www.tot.name
     * @version
     */
    public class Image extends HttpServlet {

    /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("image/jpeg");
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);
        HttpSession session=request.getSession();
        // 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(200,250));
        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(160,200));
        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
        session.setAttribute("rand",sRand);
        // 图象生效
        g.dispose();
        ServletOutputStream responseOutputStream =response.getOutputStream();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", responseOutputStream);

        //以下关闭输入流！
        responseOutputStream.flush();
        responseOutputStream.close();
    }
    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);
    }
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /** Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /** Returns a short description of the servlet.
     */
    public String getServletInfo() {
        return "Short description";
    }
    // </editor-fold>
    }

 

生成验证码的index.jsp:

<%@ page contentType="text/html;charset=gb2312"
	import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://"
			+ request.getServerName() + ":" + request.getServerPort()
			+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W 3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>认证码输入页面</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>
<body>
<form method=post action="check.jsp">
<table>
	<tr>
		<td align=left>系统产生的认证码：</td>
		<td> <img border=0 src="<%=path%>/Image"></td>
	</tr>
	<tr>
		<td align=left>输入上面的认证码：</td>
		<td><input type=text name=rand maxlength=4 value=""></td>
	</tr>
	<tr>
		<td colspan=2 align=center><input type=submit value="提交检测"></td>
	</tr>
	</form>
</body>
</html>

 

验证验证码的check.jsp:

<%@ page contentType="text/html; charset=gb2312" language="java"
	import="java.sql.*" errorPage=""%>
<html>
<head>
<title>认证码验证页面</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="0">
</head>

<body onload="/Image">
<%
	String rand = (String) session.getAttribute("rand");
	String input = request.getParameter("rand");
%>
系统产生的认证码为：
<%=rand%><br />
您输入的认证码为：
<%=input%><br />
<br />
<%
	if (rand.equals(input)) {
%>
<font color=green>输入相同，认证成功！</font>
<%
	} else {
%>
<font color=red>输入不同，认证失败！</font>
<%
	}
%>
</body>
</html>

 

 

启动服务，看看效果吧。