Complete example of jsp page verification code

This article mainly introduces the jsp page in detailVerification codeA complete example, which has certain reference and learning value for jsp. Friends who are interested in jsp can refer to this article

The project structure is as follows. Create a new Web Project in MyEclipse and name it servlet

##1. Create a new servlet class under src

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 {

  public static final char[] chars={'2','3','4','5','6','7','8','9','A'};//自定义验证码池
  public static Random random=new Random();　　//随机数
  
  public static String getRandomString(){　　//获取6位随机数，放在图片里
    StringBuffer buffer=new StringBuffer();
    for(int i=0;i<6;i++){
      buffer.append(chars[random.nextInt(chars.length)]);
    }
    return buffer.toString();
  }
  
  public static Color getRandomColor(){　　//获取随机的颜色
    return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
  }
  
  public static Color getReverseColor(Color c){　　//返回某颜色的反色
    return new Color(255 - c.getRed(), 255 - c.getGreen(), 255 - c.getBlue());
  }
  
  /**
   * Constructor of the object.
   */
  public IdentityServlet() {
    super();
  }

  /**
   * Destruction of the servlet. <br>
   */
  public void destroy() {
    super.destroy(); // Just puts "destroy" string in log
    // Put your code here
  }

  /**
   * The doGet method of the servlet. <br>
   *
   * This method is called when a form has its tag value method equals to get.
   * 
   * @param request the request send by the client to the server
   * @param response the response send by the server to the client
   * @throws ServletException if an error occurred
   * @throws IOException if an error occurred
   */
  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    response.setContentType("image/jpeg");　　//设置输出类型
    
    String randomString = getRandomString();　　//随机字符串
    request.getSession(true).setAttribute("randomString", randomString);//放到session里
    
    int width=100;　　//图片宽度
    int height=30;　　//图片高度
    
    Color color=getRandomColor();　　//随机颜色，用于背景色
    Color reverse=getReverseColor(color);//反色，用于前景色
    //创建一个彩色图片
    BufferedImage bi=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    Graphics2D g=bi.createGraphics();　　//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);//绘制随机字符
    for(int i=0,n=random.nextInt(100);i<n;i++){　　//画最多100个噪音点
      g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
    }
    ServletOutputStream out= response.getOutputStream();//转成JPEG格式
    JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);//编码器
    encoder.encode(bi);　　//对图片进行编码
    out.flush();　　//输出到客户端
  }

  /**
   * The doPost method of the servlet. <br>
   *
   * This method is called when a form has its tag value method equals to post.
   * 
   * @param request the request send by the client to the server
   * @param response the response send by the server to the client
   * @throws ServletException if an error occurred
   * @throws IOException if an error occurred
   */
  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    doGet(request, response);
  }

  /**
   * Initialization of the servlet. <br>
   *
   * @throws ServletException if an error occurs
   */
  public void init() throws ServletException {
    // Put your code here
  }

}

2 , web.xml, the configuration of servlet and servlet-mapping will be automatically generated:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
  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_3_0.xsd">
 <display-name></display-name>
 <servlet>
  <servlet-name>IdentityServlet</servlet-name>
  <servlet-class>com.servlet.IdentityServlet</servlet-class>
 </servlet>

 <servlet-mapping>
  <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>

3. Create a new html under WebRoot and display the verification code

<!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 type="text/javascript">
function reloadImage(){
  document.getElementById(&#39;btn&#39;).disabled=true;
  document.getElementById(&#39;identity&#39;).src=&#39;servlet/IdentityServlet?ts=&#39;+new Date().getTime();
}
</script>
</head>

<body>

<img src="servlet/IdentityServlet" id="identity" onload="btn.disabled=false;" />
<input type=button value="换个图片" onclick="reloadImage()" id="btn">
</body>
</html>

Start Tomcat and enter the URL:

http://localhost:8080/servlet/identity.html, the effect is as follows:

Click 'Change Picture', a new verification code will be generated.

The above is the entire content of this article, I hope it will be helpful to everyone’s study! !

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