Question

jsp中如何添加验证码？

或者是字母数字组合。

Answer 1

<%@ 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.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();

// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
%>

Answer 2

呵呵，声明下是转的别人的代码
package util;

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.awt.*;
import java.awt.image.*;
import java.util.*;
import javax.imageio.*;

public class AuthImg extends HttpServlet
{

private static final long serialVersionUID = 1L;
//@SuppressWarnings("unused")
public void init() throws ServletException
{
super.init();
}
Color getRandColor(Random random,int fc,int bc)
{
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 service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");

int width=105, height=30;

//这里是一些汉字，你可以进行编码转换，添加其他汉字
String base = "u53d4u80ccu7ec6";

int length = base.length();

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

Random random = new Random();

g.setColor(getRandColor(random,200,250));
g.fillRect(0, 0, width, height);

String[] fontTypes = {"u5b8bu4f53","u65b0u5b8bu4f53","u9ed1u4f53","u6977u4f53","u96b6u4e66"};
int fontTypesLength = fontTypes.length;

g.setColor(getRandColor(random,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++)
{
int start = random.nextInt(length);
String rand=base.substring(start,start+1);
sRand+=rand;

g.setColor(getRandColor(random,10,150));

g.setFont(new Font(fontTypes[random.nextInt(fontTypesLength)],Font.BOLD,18 + random.nextInt(6)));

g.drawString(rand,23*i+ 0 + random.nextInt(8),21);
}

HttpSession session = request.getSession(true);
session.setAttribute("checkcode",sRand);

g.dispose();

ImageIO.write(image, "JPEG", response.getOutputStream());
}
public void destroy()
{
}
}

Answer 3

可以生成一个背景，然后随机产生文字或数字组合之类的就可以了。