使用基本servlet技术生产图片验证码

最新推荐文章于 2024-10-27 12:03:55 发布

原创最新推荐文章于 2024-10-27 12:03:55 发布 · 194 阅读

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#servlet 验证码 js

本文介绍了一种使用Java Servlet生成包含随机字符的验证码图片的方法。通过定义一个Servlet来生成带有随机字符串的图片，并将其输出到客户端。该实现还包含了颜色随机、背景噪声绘制等功能，确保了验证码的安全性和用户体验。

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servlet的代码：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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

@SuppressWarnings("serial")
public class IdentityServlet extends HttpServlet {
	public static final char[] chs = {'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K',
		'L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'};
	public static Random random = new Random();
	
	public static String getRandomString(){
		StringBuffer buffer = new StringBuffer();
		
		for (int i = 0; i < 6; i++) {
			buffer.append(chs[random.nextInt(chs.length)]);
		}
		
		return buffer.toString();
	}
	
	public static Color getRandomColor(){
		return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
	}
	
	public static Color getReverseColor(Color c){
		return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
	}

	public void doGet(HttpServletRequest req , HttpServletResponse resp ) throws IOException {
		resp.setContentType("image/jpeg");
		String randomString = getRandomString();
		
		req.getSession(true).setAttribute("randomString" , randomString);
		
		int width = 100;
		int height = 30;
		
		Color color = getRandomColor();
		Color reverse = getReverseColor(color);
		
		BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		
		Graphics2D g = bi.createGraphics();
		
		g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
		g.setColor(color);
		g.fillRect(0, 0, width, height);
		g.setColor(reverse);
		g.drawString(randomString, 18, 20);
		for (int i = 0 , n = random.nextInt(100); i < n; i++) {
			g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
		}
		
		ServletOutputStream out = resp.getOutputStream();
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
		
		encoder.encode(bi);
		out.flush();
	}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>LoginServlet</display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
  	<servlet-name>identity</servlet-name>
  	<servlet-class>com.qf.servlet.IdentityServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>identity</servlet-name>
  	<url-pattern>/identity</url-pattern>
  </servlet-mapping>
</web-app>

index.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="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>
</head>
<body>
   <script type="text/javascript">
   	function reloadImage(){
   		document.getElementById('btn').disabled = true;
   		document.getElementById('identity').src = 'identity';
   	}
   </script>
   <img onLoad = "" src="identity" id="identity" />
   <input type="submit" value="提交" id="btn" onclick="reloadImage();">  
</body>
</html>