生成验证码的java代码

Ⅰ 用java生成6位验证码，由大小写数字组成，不能重复字符

生成随机可以用Random类，不能重复可以考虑放在HashSet中，因为HashSet的值是不能重复的，看代码如下：

{
	publicstaticvoidmain(String[]args){
		
	Set<String>store=getletterandnum(6);
	
	printSet(store);
			
	}

	publicstaticSet<String>getletterandnum(intlength){
		
		Set<String>set=newHashSet<String>();

		for(inti=0;i<length;i++){

			Stringvalue=getrandom();
			
			set.add(value);
		}
		
		if(set.size()<length){//如果没有生成6位
			
			Stringvalue=getrandom();//继续调用生成随机数的方法
			
			set.add(value);
			
		}
		
		returnset;
	}

	privatestaticStringgetrandom(){//生成随机字母和数字方法
		
		Stringvalue="";

		Randomrandom=newRandom();
		
		intgen=random.nextInt(2);//0、1、2

		Stringcharornum=gen%2==0?"char":"num";

		if("char".equals(charornum)){

			inttemp=random.nextInt(2)%2==0?65:97;

			intascii=random.nextInt(26);
			
			value+=(char)(ascii+temp);

		}elseif("num".equalsIgnoreCase(charornum)){

			value+=String.valueOf(random.nextInt(10));
		}
		returnvalue;
	}

	publicstaticvoidprintSet(Setset){//打印set的方法
		
	Iteratoriterator=set.iterator();
	while(iterator.hasNext()){
		Stringele=(String)iterator.next();
		System.out.print(ele+"");
		
	}
		
	}
	

Ⅱ 用java怎么制作验证码

原理:

1.随机生成4个数字 用到了Random类
2.对这4个数字设置字体格式 用 setFont方法
3.改变字体颜色用setColor 然后随机生成颜色

代码如下
package s1;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.jms.Session;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class GetImage extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

this.doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 发送图片不能够添加这2行代码
// response.setContentType("text/html;charset=UTF-8");
// request.setCharacterEncoding("UTF-8");

int width=100;
int height=50;
//获得一张图片
BufferedImage image=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics g=image.getGraphics();
g.setColor(Color.WHITE);
g.fillRect(1, 1, width-2, height-2);
g.setFont(new Font("宋体",Font.BOLD,30));
Random random=new Random();

/虚枯兄/ 填充的字符串
String str="";

//缓存生成的验证码败橘
StringBuffer stringbuffer=new StringBuffer();

//随机生成验证码的颜差袭色和字符
for(int i=0;i<4;i++)
{ //设置随机颜色
g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));

int index=random.nextInt(62);//这里的62就是从填充字符段中随意选取一个位置
String str1=str.substring(index,index+1);
g.drawString(str1, 20*i, 30);//x,y数值设置太小会显示不出来
stringbuffer.append(str1);
}

//将生成的验证码存到服务器
request.getSession().setAttribute("checkcode", stringbuffer.toString());//key和value

//将图片发送给浏览器
ImageIO.write(image, "jpg", response.getOutputStream());

}

}

用户登录界面代码
package s1;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class Login extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("text/html;charset=UTF-8");// 设置服务器发送给浏览器的编码方式
request.setCharacterEncoding("UTF-8"); // 客户端向服务器提交的数据的解码方式
// 获得用户提交的数据
String checkcode = request.getParameter("checkcode");
System.out.println(checkcode);

// 判断输入的验证码是不是符合
HttpSession session = request.getSession();// session是存放数据的地方
String str = (String) session.getAttribute("checkcode");

if (str != null) {
if (checkcode.compareToIgnoreCase(str) == 0) // 验证码忽略大小写
response.getWriter().println("验证码输入正确");

else
response.getWriter().println("验证码输入错误");
}

else response.getWriter().println("验证码失效");

// 使用完的验证码信息要删除,返回原页面再输一次,验证码就失效了
session.removeAttribute("checkcode");

}

}

Ⅲ 用java随机生成四位验证码，只求编程代码

我自己做的系磨厅统里面用作验证码的JSP的
<%@page contentType="image/jpeg;charset=utf-8"%>
<%@page import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*" %>
<%@ page import="java.io.OutputStream" %>
<html>
<body>
<%!
Color getRandColor(int fc,int bc)
{
Random rd=new Random();
if(fc>255) fc=255;
if(bc>255) bc=255;
int red=fc+rd.nextInt(bc-fc);
int green=fc+rd.nextInt(bc-fc);
int blue=fc+rd.nextInt(bc-fc);
return new Color(red,green,blue);
}
%>
<%
Random r=new Random();
response.addHeader("Pragma","No-cache");
response.addHeader("Cache-Control","no-cache");
response.addDateHeader("expires",0);
int width=90;
int height=23;
BufferedImage pic=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics gc=pic.getGraphics();
gc.setColor(getRandColor(200,250));
gc.fillRect(0,0,width,height);
String[] rNum ={"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",
"耐游神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"};
int[] style = {Font.PLAIN,Font.BOLD,Font.ITALIC,Font.PLAIN+Font.BOLD,
Font.BOLD+Font.ITALIC,Font.PLAIN+Font.ITALIC,Font.PLAIN+Font.BOLD+Font.ITALIC};
gc.setColor(Color.WHITE);
gc.drawLine(0,30,90,10);
gc.setColor(getRandColor(160,200));
for (int i=0;i<昌亏50;i++)
{
int x = r.nextInt(width);
int y = r.nextInt(height);
int xl = r.nextInt(10);
int yl = r.nextInt(10);
gc.drawLine(x,y,x+xl,y+yl);
}
gc.setColor(getRandColor(60,150));
String rt = "";
for(int i=0;i<4;i++){
String temp = rNum[r.nextInt(62)];
rt = rt+temp;
gc.setFont(new Font("Times New Roman",style[r.nextInt(7)],15));
gc.drawString(temp,5+i*15+r.nextInt(10),10+r.nextInt(10));
}
gc.dispose();
session.setAttribute("randNum",rt);
OutputStream os=response.getOutputStream();
ImageIO.write(pic,"JPEG",os);
System.out.println("当前验证码为:"+session.getAttribute("randNum"));
os.flush();
os.close();
os=null;
response.flushBuffer();
out.clear();
out = pageContext.pushBody();
%>
</body>
</html>

Ⅳ 怎样用java实现验证码

现在许多系统的注册 登录或者发布信息模块都添加的随机验证码功能 就是为了避免自动注册程序或者自动发布程序的使用

验证码实际上就是随机选择一些字符以图片的形式展现在页面上 如果进行提交操作的同时需要将图片上的字符同时提交 如果提交的字符与服务器session保存的不同 则认为提交基数信息无效 为了避免自动程序分析解析图片 通常会在图片上随机生成一些干扰线或者将字符进行扭曲 增加自动识别验证码的难度

在这里 我们使用java实现验证码

<%@ 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> ) fc= ;

租锋做if(bc> ) bc= ;

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 );

弊衡response setHeader( Cache Control no cache );

response setDateHeader( Expires );

// 在内存中创建图象

int width= height= ;

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( ));

g fillRect( width height);

//设定字体

g setFont(new Font( Times New Roman Font PLAIN ));

// 随机产生 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( ));

for (int i= ;i< ;i++)

{

int x = random nextInt(width);

int y = random nextInt(height);

int xl = random nextInt( );

int yl = random nextInt( );

g drawLine(x y x+xl y+yl);

}

// 取随机产生的认证码( 位数字)

String codeList = ;

String sRand= ;

for (int i= ;i< ;i++){

int a=random nextInt(codeList length() );

String rand=codeList substring(a a+ );

sRand+=rand;

// 将认证码显示到图象中

g setColor(new Color( +random nextInt( ) +random nextInt( ) +random nextInt( )));//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 *i+ );

}

// 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());

out clear();

out = pageContext pushBody();