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  • 通过Servlet的response绘制页面验证码

    java部分

    package com.servlet;
    
    import java.awt.Color;
    import java.awt.Font;
    import java.awt.Graphics2D;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.Random;
    
    import javax.servlet.ServletException;
    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;
    
    public class IdentityServlet extends HttpServlet {
        //不包括0,O,1,I等难以辨认的字符
        public static final char[] CHARS={'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();
        //获取随机码
        public static String getRandomString(){
            StringBuffer buffer=new StringBuffer();
            for(int i=0;i<6;i++){
                buffer.append(CHARS[random.nextInt(CHARS.length)]);
            }
            return buffer.toString();
        }
        //获取随机颜色
        public static Color getRandomColor(){
            return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
        }
        //获取所给颜色的相反值
        public static Color getReverseColor(Color c){
            return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
        }
        
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
    
            response.setContentType("image/jpeg");//设置输出类型
            String randomString=getRandomString();//获取随机数
            request.getSession(true).setAttribute("randomString", randomString);//将随机数放入session中
            int width=100;//图片宽度
            int height=30;//图片高度
            
            Color color=getRandomColor();//获取颜色,用于背景色
            Color reverse=getReverseColor(color);//发色,用于前背景
            
            BufferedImage bi=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//创建一个彩色图片
            
            Graphics2D g=bi.createGraphics();//获取绘图对象
            g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
            g.setColor(color);//设置颜色
            g.fillRect(0, 0, width, height);//绘制背景
            g.setColor(reverse);
            g.drawString(randomString, 18, 20);//设置颜色
            
            //绘制遭点
            for(int i=0, n=random.nextInt(50);i<n;i++){
                g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
            }
            ServletOutputStream out=response.getOutputStream();
            JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);
            encoder.encode(bi);
            out.flush();
            
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
    
        }
        
    }

    web.xml部分

    <?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
        http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
      <display-name></display-name>
      
      <servlet>
        <servlet-name>IdentityServlet</servlet-name>
        <servlet-class>com.servlet.IdentityServlet</servlet-class>
      </servlet>
    
        <servlet-name>IdentityServlet</servlet-name>
        <url-pattern>/servlet/IdentityServlet</url-pattern>
      </servlet-mapping>    
      <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

    html部分

    <%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    <%
    String path = request.getContextPath();
    String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
    %>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <script type="text/javascript">
        	function reloadImage(){
        		document.getElementById('btn').disabled=true;
            	document.getElementById('identity').src='servlet/IdentityServlet?ts='+new Date().getTime();
        	}
        </script>
      </head>
      
      <body>
        <img src="servlet/IdentityServlet" id='identity' onclick="btn.disabled=false;"/>
        <input type="button" value="换一个" onclick="reloadImage()" id='btn'>
      </body>
    </html>
    

    运行结果:

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  • 原文地址:https://www.cnblogs.com/DeepBlues/p/3472311.html
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