jsp+Servlet编程实现验证码的方法

2024-09-05 00:22:24

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这篇文章主要介绍了jsp+Servlet编程实现验证码的方法,结合实例分析了jsp+servlet实现验证码所需的相关类与具体功能实现技巧,具有一定参考借鉴价值,需要的朋友可以参考下

本文实例讲述了jsp+Servlet编程实现验证码的方法。分享给大家供大家参考，具体如下：

这里用到两个类，一个用于验证码实现，一个为后台Servlet验证输入是否正确：

jsp+Servlet编程实现验证码的方法

CodeUtil.java--------验证码具体实现：

package util;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.OutputStream;

import java.io.PrintWriter;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpSession;

import javax.servlet.jsp.PageContext;

import javax.servlet.jsp.tagext.BodyContent;

import com.sun.image.codec.jpeg.JPEGCodec;

import com.sun.image.codec.jpeg.JPEGImageDecoder;

import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class CodeUtil extends HttpServlet {

public void service(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//System.out.println("哈哈哈");

response.setContentType("image/jpeg");

//设置页面不缓存

response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

//在内存中创建图像

int width = 90;

int height = 35;

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

//获取图形上下文

Graphics g = image.getGraphics();

//随机类

Random random = new Random();

//设定背景

g.setColor(getRandColor(200, 250));

g.fillRect(0, 0, width, height);

//设定字体

g.setFont(new Font("Times New Roman",Font.PLAIN,30));

//随机产生干扰线

g.setColor(getRandColor(160, 200));

for (int i = 0; i < 100; 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);

}

//随机产生4位验证码

String[] codes = {"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","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"};

String code = "";

for(int i=0;i<4;i++){

String str = codes[random.nextInt(codes.length)];

code += str;

// 将认证码显示到图象中

g.setColor(new Color(50 + random.nextInt(110), 20 + random.nextInt(110), 30 + 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(str, 18 * i +13, 27); //文字间距*i+距离左边距，上边距

}

HttpSession session=request.getSession();

// 将认证码存入SESSION

session.setAttribute("code", code);

// 图象生效

g.dispose();

// 输出图象到页面

ImageIO.write(image, "JPEG", response.getOutputStream());

//加上下面代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has already been called ..........等异常

response.getOutputStream().flush();

response.getOutputStream().close();

response.flushBuffer();

}

//获取随机颜色

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);

}

}

CheckCodeUtil.java-----------用户输入验证功能

package util;

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 CheckCodeUtil extends HttpServlet {

public void service(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

request.setCharacterEncoding("utf-8");

response.setContentType("text/html;charset=utf-8");

PrintWriter out = response.getWriter();

//从session获取验证码

HttpSession session=request.getSession();

String code=session.getAttribute("code").toString();

System.out.println(code);

//获取用户输入验证码

String input=request.getParameter("code");

System.out.println(input);

if(code.equalsIgnoreCase(input)){

//转发数据

request.setAttribute("result", "true");

request.getRequestDispatcher("test/regist.jsp").forward(request, response);

// response.sendRedirect(request.getContextPath()+"/regist/regist.jsp");

}else{

request.setAttribute("result", "false");

request.getRequestDispatcher("test/regist.jsp").forward(request, response);

}

}

}

测试页面效果：

jsp+Servlet编程实现验证码的方法

测试页面代码：

<%@ page session="true" pageEncoding="utf-8" contentType="text/html; charset=utf-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Insert title here</title>

<script>

function showResult1(){

alert('输入正确');

}

function showResult2(){

alert('输入错误');

}

</script>

</head>

<%

response.setContentType("text/html;charset=utf-8");

request.setCharacterEncoding("utf-8");

String path=request.getContextPath();

if(request.getAttribute("result")!=null){

String result=request.getAttribute("result").toString();

out.print(result);

if(result.equals("true")){

out.print("true");

out.print("<script>showResult1();<script>");

}else{

out.print("<script>showResult2();<script>");

}

}

%>

<body>

<br>验证码演示

<form action="<%=path %>/checkCodeUtil" method="post">

<input type="text" size="10" name="code"/>

<img src="<%=path %>/codeUtil" id="img"/>

<a href="javascript:;" onclick="document.

getElementById('img').src='<%=path %>/codeUtil?'+new Date().getTime();">看不清，换一个</a>

<input type="submit" value="提交">

</form>

</body>

</html>