<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%
// 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();
// 设定背景色
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, width, height);
//画边框
g.setColor(Color.black);
g.drawRect(0,0,width-1,height-1);
// 取随机产生的认证码(4位数字)
String rand = request.getParameter("rand");
rand = rand.substring(0,rand.indexOf("."));
switch(rand.length())
{
case 1: rand = "000"+rand; break;
case 2: rand = "00"+rand; break;
case 3: rand = "0"+rand; break;
default: rand = rand.substring(0,4); break;
}
// 将认证码存入SESSION
session.setAttribute("rand",rand);
// 将认证码显示到图象中
g.setColor(Color.black);
Integer tempNumber = new Integer(rand);
String numberStr = tempNumber.toString();
g.setFont(new Font("Atlantic Inline",Font.PLAIN,18));
String Str = numberStr.substring(0,1);
g.drawString(Str,8,17);
Str = numberStr.substring(1,2);
g.drawString(Str,20,15);
Str = numberStr.substring(2,3);
g.drawString(Str,35,18);
Str = numberStr.substring(3,4);
g.drawString(Str,45,15);
// 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到
Random random = new Random();
for (int i=0;i<20;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
g.drawOval(x,y,0,0);
}
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
生成有4个随机数字和杂乱背景的图片，数字和背景颜色会改变，服务器端刷新（用history.go(-1)也会变）
产生验证码图片的文件image.jsp
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
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);
}
%>
<%
//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.Of(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();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
使用验证码图片的文件a.jsp
<%@ page contentType="text/html;charset=gb2312" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>认证码输入页面</title>
< http-equiv="Content-Type" content="text/html; charset=gb2312">
< HTTP-EQUIV="Pragma" CONTENT="no-cache">
< HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
< 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="/image.jsp"></td>
</tr>
<tr>
<td align=left>输入上面的认证码：</td>
<td><input type=text name=rand maxlength=4 =""></td>
</tr>
<tr>
<td colspan=2 align=center><input type=submit ="提交检测"></td>
</tr>
</form>
</body>
</html>
验证的页面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>
< http-equiv="Content-Type" content="text/html; charset=gb2312">
< HTTP-EQUIV="Pragma" CONTENT="no-cache">
< HTTP-EQUIV="Cache-Control" CONTENT="no-cache">
< HTTP-EQUIV="Expires" CONTENT="0">
</head>
<body>
<%
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>
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%
// 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();
// 设定背景色
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, width, height);
//画边框
g.setColor(Color.black);
g.drawRect(0,0,width-1,height-1);
// 取随机产生的认证码(4位数字)
String rand = request.getParameter("rand");
rand = rand.substring(0,rand.indexOf("."));
switch(rand.length())
{
case 1: rand = "000"+rand; break;
case 2: rand = "00"+rand; break;
case 3: rand = "0"+rand; break;
default: rand = rand.substring(0,4); break;
}
// 将认证码存入SESSION
session.setAttribute("rand",rand);
// 将认证码显示到图象中
g.setColor(Color.black);
Integer tempNumber = new Integer(rand);
String numberStr = tempNumber.toString();
g.setFont(new Font("Atlantic Inline",Font.PLAIN,18));
String Str = numberStr.substring(0,1);
g.drawString(Str,8,17);
Str = numberStr.substring(1,2);
g.drawString(Str,20,15);
Str = numberStr.substring(2,3);
g.drawString(Str,35,18);
Str = numberStr.substring(3,4);
g.drawString(Str,45,15);
// 随机产生88个干扰点，使图象中的认证码不易被其它程序探测到
Random random = new Random();
for (int i=0;i<20;i++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
g.drawOval(x,y,0,0);
}
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
另外一种:
生成验证码文件：
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
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);
}
%>
<%
out.clear();//这句针对resin服务器，如果是tomacat可以不要这句
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
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);
}
String sRand="";
for (int i=0;i<4;i++){
String rand=String.Of(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
// 将认证码存入SESSION
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
验证：
<%
//读取提交的表单内容
String rand=(String)session.getAttribute("rand");
String input=request.getParameter("rand");
if (rand.equals(input))
{
response.sendRedirect("success.jsp");
}
else
{
.....
}
%>
html代码自己写
servlet验证码程序
/*
*生产随机显示的验证码图片
*
*/
package webutil;
import java.io.*;
import javax.servlet.http.*;
import javax.servlet.*;
import java.util.*;
import java.util.Random;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;
//import com.sun.image.codec.jpeg.*;
public class VImage extends HttpServlet
{
public void init(ServletConfig conf) throws ServletException
{
super.init(conf);
}
public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException
{
res.setContentType("image/jpeg");
res.setHeader("Pragma","No-cache");
res.setHeader("Cache-Control","no-cache");
res.setDateHeader("Expires", 0);
HttpSession session = req.getSession();
// 在内存中创建图象
int width=86, 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);
}
String rstr = "";
RandomStrg rst = new RandomStrg();
rst.setCharset("a-zA-Z0-9");
rst.setLength("6");
try {
rst.generateRandomObject();
rstr = rst.getRandom();
} catch (Exception ex) {
ex.printStackTrace();
}
// 取随机产生的认证码(4位数字)
String sRand="";
sRand = rstr;
for (int i=0;i<sRand.length();i++)
{
// String rand=String.Of(random.nextInt(10));
String rand = String.Of(rstr.charAt(i));
// 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("post_validate_code",sRand);
// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", res.getOutputStream());
//JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(res.getOutputStream());
//encoder.encode(image);
}
public void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException
{
doGet(req,res);
}
//给定范围获得随机颜色
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);
}
}
//随机字符串bean
package mycollect;
import java.util.*;
import java.security.SecureRandom;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
public class RandomStrg {
private String randomstr;
private boolean allchars = false;
//欠缺是8位字符串
private Integer length = new Integer(8);
private HashMap hmap;
private ArrayList lower = null;
private ArrayList upper = null;
private char[] single = null;
private int singlecount = 0;
private boolean singles = false;
private String algorithm = null;
private String provider = null;
private boolean secure = false;
private Random random = null;
private SecureRandom secrandom = null;
private final float getFloat() {
if (random == null)
return secrandom.nextFloat();
else
return random.nextFloat();
}
/**
* generate the Random object that will be used for this random number
* generator
*
*/
public final void generateRandomObject() throws Exception {
// check to see if the object is a SecureRandom object
if (secure) {
try {
// get an instance of a SecureRandom object
if (provider != null)
// search for algorithm in package provider
random = SecureRandom.getInstance(algorithm, provider);
else
random = SecureRandom.getInstance(algorithm);
} catch (NoSuchAlgorithmException ne) {
throw new Exception(ne.getMessage());
} catch (NoSuchProviderException pe) {
throw new Exception(pe.getMessage());
}
} else
random = new Random();
}
/**
* generate the random string
*
*/
private final void generaterandom() {
if (allchars)
for (int i = 0; i < length.int(); i++)
randomstr = randomstr + new Character((char)((int) 34 +
((int)(getFloat() * 93)))).toString();
else if (singles) {
// check if there are single chars to be included
if (upper.size() == 3) {
// check for the number of ranges max 3 uppercase lowercase digits
// build the random string
for (int i = 0; i < length.int(); i++) {
// you have four groups to choose a random number from, to make
// the choice a little more random select a number out of 100
// get a random number even or odd
if (((int) (getFloat() * 100)) % 2 == 0) {
// the number was even get another number even or odd
if (((int) (getFloat() * 100)) % 2 == 0)
// choose a random char from the single char group
randomstr = randomstr + randomSingle().toString();
else
// get a random char from the first range
randomstr = randomstr + randomChar((Character)lower.get(2),
(Character)upper.get(2)).toString();
} else {
// the number was odd
if (((int) (getFloat() * 100)) % 2 == 0)
// choose a random char from the second range
randomstr = randomstr + randomChar((Character)lower.get(1),
(Character)upper.get(1)).toString();
else
// choose a random char from the third range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
}
} else if (upper.size() == 2) {
// single chars are to be included choose a random char from
// two different ranges
// build the random char from single chars and two ranges
for (int i = 0; i < length.int(); i++) {
// select the single chars or a range to get each random char
// from
if (((int)(getFloat() * 100)) % 2 == 0) {
// get random char from the single chars
randomstr = randomstr + randomSingle().toString();
} else if (((int) (getFloat() * 100)) % 2 == 0) {
// get the random char from the first range
randomstr = randomstr + randomChar((Character)lower.get(1),
(Character)upper.get(1)).toString();
} else {
// get the random char from the second range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
}
} else if (upper.size() == 1) {
// build the random string from single chars and one range
for (int i = 0; i < length.int(); i++) {
if (((int) getFloat() * 100) % 2 == 0)
// get a random single char
randomstr = randomstr + randomSingle().toString();
else
// get a random char from the range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
} else {
// build the rand string from single chars
for (int i = 0; i < length.int(); i++)
randomstr = randomstr + randomSingle().toString();
}
} else {
// no single chars are to be included in the random string
if (upper.size() == 3) {
// build random strng from three ranges
for (int i = 0; i < length.int(); i++) {
if (((int) (getFloat() * 100)) % 2 == 0) {
// get random char from first range
randomstr = randomstr + randomChar((Character)lower.get(2),
(Character)upper.get(2)).toString();
} else if (((int) (getFloat() * 100)) % 2 == 0) {
// get random char form second range
randomstr = randomstr + randomChar((Character)lower.get(1),
(Character)upper.get(1)).toString();
} else {
// get random char from third range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
}
} else if (upper.size() == 2) {
// build random string from two ranges
for (int i = 0; i < length.int(); i++) {
if (((int) (getFloat() * 100)) % 2 == 0)
// get random char from first range
randomstr = randomstr + randomChar((Character)lower.get(1),
(Character)upper.get(1)).toString();
else
// get random char from second range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
} else
// build random string
for (int i = 0; i < length.int(); i++)
// get random char from only range
randomstr = randomstr + randomChar((Character)lower.get(0),
(Character)upper.get(0)).toString();
}
}
/**
* generate a random char from the single char list
*
* @returns - a randomly selscted character from the single char list
*
*/
private final Character randomSingle() {
return (new Character(single[(int)((getFloat() * singlecount) - 1)]));
}
/**
* generate a random character
*
* @param lower lower bound from which to get a random char
* @param upper upper bound from which to get a random char
*
* @returns - a randomly generated character
*
*/
private final Character randomChar(Character lower, Character upper) {
int tempval;
char low = lower.char();
char up = upper.char();
// get a random number in the range lowlow - lowup
tempval = (int)((int)low + (getFloat() * ((int)(up - low))));
// return the random char
return (new Character((char) tempval));
}
/**
* get the randomly created string for use with the
* <jsp:getProperty name=<i>"id"</i> property="randomstr"/>
*
* @return - randomly created string
*
*/
public final String getRandom() {
randomstr = new String();
generaterandom(); // generate the first random string
if (hmap != null) {
while (hmap.containsKey(randomstr)) {
// random string has already been created generate a different one
generaterandom();
}
hmap.put(randomstr, null); // add the new random string
}
return randomstr;
}
/**
* set the ranges from which to choose the characters for the random string
*
* @param low set of lower ranges
* @param up set of upper ranges
*
*/
public final void setRanges(ArrayList low, ArrayList up) {
lower = low;
upper = up;
}
/**
* set the hashmap that is used to check the uniqueness of random strings
*
* @param map hashmap whose keys are used to insure uniqueness of random strgs
*
*/
public final void setHmap(HashMap map) {
hmap = map;
}
/**
* set the length of the random string
*
* @param length of the random string
*
*/
public final void setLength(String ) {
length = new Integer();
}
/**
* set the algorithm name
*
* @param name of the algorithm to use for a SecureRandom object
*
*/
public final void setAlgorithm(String ) {
algorithm = ;
secure = true; // a SecureRandom object is to be used
}
/**
* set the provider name
*
* @param name of the package to check for the algorithm
*
*/
public final void setProvider(String ) {
provider = ;
}
/**
* set the allchars flag
*
* @param boolean of the allchars flag
*
*/
public final void setAllchars(boolean ) {
allchars = ;
}
/**
* set the array of single chars to choose from for this random string and the
* number of chars in the array
*
* @param chars the array of single chars
* @param the number of single chars
*
*/
public final void setSingle(char[] chars, int ) {
single = chars; // set the array of chars
singlecount = ; // set the number of chars in array single
singles = true; // set flag that single chars are in use
}
public final void setCharset(String )
{
// s tells the method whether or not to check for single chars
boolean more = true;
// create the arraylists to hold the upper and lower bounds for the char
// ranges
lower = new ArrayList(3);
upper = new ArrayList(3);
// user has chosen to use all possible characters in the random string
if (.compareTo("all") == 0) {
allchars = true; // set allchars flag
// all chars are to be used so there are no single chars to sort
// through
more = false;
}else if ((.charAt(1) == '-') && (.charAt(0) != '\\')) {
// run through the ranges at most 3
while (more && (.charAt(1) == '-')){
// check to make sure that the dash is not the single char
if (.charAt(0) == '\\')
break;
else {
// add upper and lower ranges to there list
lower.add(new Character(.charAt(0)));
upper.add(new Character(.charAt(2)));
}
// check to see if there is more to the charset
if (.length() <= 3)
more = false;
else
// create a new string so that the next range if there is one
// starts it
= .substring(3);
}
}
// if more = false there are no single chars in the charset
if (more) {
single = new char[30]; // create single
// create a set of tokens from the string of single chars
StringTokenizer tokens = new StringTokenizer();
while (tokens.hasMoreTokens()) {
// get the next token from the string
String token = tokens.nextToken();
if (token.length() > 1)
// char is a - add it to the list
single[singlecount++] = '-';
// add the current char to the list
single[singlecount++] = token.charAt(0);
}
}
if ((lower == null) && (single == null))
setCharset("a-zA-Z0-9");
}
}
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### jsp验证码刷新功能 在Web开发中，验证码（CAPTCHA）被广泛应用于表单提交、用户登录等场景，以防止自动化的恶意攻击或垃圾信息的提交。而在JSP技术中实现验证码的刷新功能，不仅可以提升用户体验，还能进一步...
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