此servlet生成一个验证码图片可以通过请求参数设置此图片/* * 创建日期 2006-7-23 * * TODO 要更改此生成的文件的模板，请转至 * 窗口 － 首选项 － Java － 代码样式 － 代码模板 * 参数： * count:验证码的字符个数 * width:验证码图片宽度 * height:验证码图片高度 * type:类型 0-纯数字 1-纯大写字母 2-数字和大学字母混合 * 功能：生成验证码图片，将验证码保存进session里 */package hrl.util;import java.io.IOException;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.awt.*;import java.awt.image.*;import java.util.*;import javax.imageio.*;/** * @author Administrator * * TODO 要更改此生成的类型注释的模板，请转至 * 窗口 － 首选项 － Java － 代码样式 － 代码模板 */public class ValidateCodeServlet extends HttpServlet {        private final int TYPE_NUMBER = 0;    private final int TYPE_LETTER = 1;    private final int TYPE_MULTIPLE = 2;    private int width;    private int height;    private int count;    private int type;    private String  validate_code;    private Random random;    private Font font;    private int line;    public void init(ServletConfig config) throws ServletException {        super.init(config);        //TODO Method stub generated by Lomboz        width = 150;        height = 50;        count = 4;        type = TYPE_NUMBER;        random = new Random();        line = 200;    }    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        //TODO Method stub generated by Lomboz        response.setHeader("Pragma","No-cache");        response.setHeader("Cache-Control","no-cache");        response.setDateHeader("Expires", 0);        response.setContentType("image.jpeg");        String reqCount = request.getParameter("count");        String reqWidth = request.getParameter("width");        String reqHeight = request.getParameter("height");        String reqType = request.getParameter("type");        if(reqCount!=null && reqCount!="")this.count = Integer.parseInt(reqCount);        if(reqWidth!=null && reqWidth!="")this.width = Integer.parseInt(reqWidth);        if(reqHeight!=null && reqHeight!="")this.height = Integer.parseInt(reqHeight);        if(reqType!=null && reqType!="")this.type = Integer.parseInt(reqType);        font = new Font("Courier New",Font.BOLD,width/count);        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);        Graphics g = image.getGraphics();        g.setColor(getRandColor(200,250));        g.fillRect(0, 0, width, height);        g.setColor(getRandColor(160,200));        for (int i=0;i<line;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);        }        g.setFont(font);        validate_code = getValidateCode(count,type);        request.getSession().setAttribute("validate_code",validate_code);        for (int i=0;i<count;i++){            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            int x = (int)(width/count)*i;            int y = (int)((height+font.getSize())/2)-5;            g.drawString(String.valueOf(validate_code.charAt(i)),x,y);        }        g.dispose();        ImageIO.write(image, "JPEG", response.getOutputStream());    }    protected void doPost(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        //TODO Method stub generated by Lomboz        doGet(request, response);    }        private Color getRandColor(int from,int to){        Random random = new Random();        if(to>255) from=255;        if(to>255) to=255;        int rang = Math.abs(to - from);        int r=from+random.nextInt(rang);        int g=from+random.nextInt(rang);        int b=from+random.nextInt(rang);        return new Color(r,g,b);    }        private String getValidateCode(int size,int type){        StringBuffer validate_code = new StringBuffer();        for(int i = 0; i < size; i++){            validate_code.append(getOneChar(type));        }        return validate_code.toString();    }    private String getOneChar(int type){        String result = null;        switch(type){            case TYPE_NUMBER:                result = String.valueOf(random.nextInt(10));                break;                            case TYPE_LETTER:                result = String.valueOf((char)(random.nextInt(26)+65));                break;                        case TYPE_MULTIPLE:                if(random.nextBoolean()){                    result = String.valueOf(random.nextInt(10));                }else{                    result = String.valueOf((char)(random.nextInt(26)+65));                }                break;            default:                result=null;                break;        }        if(result==null)throw new NullPointerException("获取验证码出错");        return result;    }}web.xml配置：<servlet><servlet-name>yan</servlet-name><display-name>yan</display-name><description>yan</description><servlet-class>hrl.util.ValidateCodeServlet</servlet-class></servlet><servlet><servlet-mapping><servlet-name>yan</servlet-name><url-pattern>/ValidateCodeServlet</url-pattern></servlet-mapping><servlet-mapping>实例：show.jsp:<%@ page language="java" pageEncoding="GB2312" %><!DOCTYPE HTML PUBLIC "-//w3c//dtd html 4.0 transitional//en"><html><head><title>Lomboz JSP</title></head><body bgcolor="#FFFFFF"><form action="heck.jsp" method=post><table align=center><tr><td>请输入验证码：<input type='text' name='validate_code' size=20></td><td><img src="ValidateCodeServlet" width=150 height=50></td></tr><tr><td><input type="submit" value="提交"></td><td><input type="reset" value="重填"></td></tr></table></body></html>check.jsp:<%@ page language="java" pageEncoding="GB2312" %><!DOCTYPE HTML PUBLIC "-//w3c//dtd html 4.0 transitional//en"><html><head><title>Lomboz JSP</title></head><body bgcolor="#FFFFFF"><%String session_validate_code = (session.getAttribute("validate_code")).toString();if(session_validate_code==null)System.out.println("validate code has not set");else{ String request_code = request.getParameter("validate_code"); if(request_code==null)out.println("未输入"); else{  if(request_code.equalsIgnoreCase(session_validate_code))out.println("匹配");  else out.println("不匹配"); }}%></body></html>

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