Java随机验证吗

<span style="font-size:18px;">package com.java.process.jsp;

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.imageio.ImageIO;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

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<span style="font-size:18px;">
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<span style="font-size:18px;"></span><pre name="code" class="java">

<span style="font-size:18px;">//servlet3.0之前必须是在web.xml中配置</span>

<span style="font-size:18px;"></span><pre name="code" class="html"> <servlet>
    <servlet-name>validateColorServlet</servlet-name>
    <servlet-class>com.atguigu.javaweb.ValidateColorServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>validateColorServlet</servlet-name>
    <url-pattern>/validateColorServlet</url-pattern>
  </servlet-mapping>

<span style="font-size: 18px;">//servlet3.0以后就是能够直接用@WebServlet,</span>

<span style="font-size:18px;">@WebServlet("/validateColorServlet")
public class ValidateColorServlet extends HttpServlet {

public static final String CHECK_CODE_KEY = "CHECK_CODE_KEY";
	
	private static final long serialVersionUID = 1L;
	
	//设置验证图片的宽度, 高度, 验证码的个数
	private int width = 152;
	private int height = 40;
	private int codeCount = 6;
	
	//验证码字体的高度
	private int fontHeight = 4;
	
	//验证码中的单个字符基线. 即：验证码中的单个字符位于验证码图形左上角的 (codeX, codeY) 位置处
	private int codeX = 0;
	private int codeY = 0;
	
	//验证码由哪些字符组成
	char [] codeSequence = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz23456789".toCharArray();
	
	//初始化验证码图形属性
	public void init(){
		fontHeight = height - 2;
		codeX = width / (codeCount + 2);
		codeY = height - 4;
	}

	public void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//定义一个类型为 BufferedImage.TYPE_INT_BGR 类型的图像缓存
		BufferedImage buffImg = null;
		buffImg = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
	
		//在 buffImg 中创建一个 Graphics2D 图像
		Graphics2D graphics = null;
		graphics = buffImg.createGraphics();
		
		//设置一个颜色, 使 Graphics2D 对象的兴许图形使用这个颜色
		graphics.setColor(Color.WHITE);
		
		//填充一个指定的矩形: x - 要填充矩形的 x 坐标; y - 要填充矩形的 y 坐标; width - 要填充矩形的宽度; height - 要填充矩形的高度
		graphics.fillRect(0, 0, width, height);
		
		//创建一个 Font 对象: name - 字体名称; style - Font 的样式常量; size - Font 的点大小
		Font font = null;
		font = new Font("", Font.BOLD, fontHeight);
		//使 Graphics2D 对象的兴许图形使用此字体
		graphics.setFont(font);
		
		graphics.setColor(Color.BLACK);
		
		//绘制指定矩形的边框, 绘制出的矩形将比构件宽一个也高一个像素
		graphics.drawRect(0, 0, width - 1, height - 1);
		
		//随机产生 15 条干扰线, 使图像中的认证码不易被其他程序探測到
		Random random = null;
		random = new Random();
		graphics.setColor(Color.GREEN);
		for(int i = 0; i < 55; i++){
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int x1 = random.nextInt(20);
			int y1 = random.nextInt(20);
			graphics.drawLine(x, y, x + x1, y + y1);
		}
		
		//创建 randomCode 对象, 用于保存随机产生的验证码, 以便用户登录后进行验证
		StringBuffer randomCode;
		randomCode = new StringBuffer();
		
		for(int i = 0; i < codeCount; i++){
			//得到随机产生的验证码数字
			String strRand = null;
			strRand = String.valueOf(codeSequence[random.nextInt(36)]);
			
			//把正在产生的随机字符放入到 StringBuffer 中
			randomCode.append(strRand);
			
			//用随机产生的颜色将验证码绘制到图像中
			graphics.setColor(Color.BLUE);
			graphics.drawString(strRand, (i + 1)* codeX, codeY);
		}
		
		//再把存放有全部随机字符的 StringBuffer 相应的字符串放入到 HttpSession 中
		request.getSession().setAttribute(CHECK_CODE_KEY, randomCode.toString());
		
		//禁止图像缓存
		response.setHeader("Pragma", "no-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		
		//将图像输出到输出流中
		ServletOutputStream sos = null;
		sos = response.getOutputStream();
		ImageIO.write(buffImg, "jpeg", sos); 
		sos.close();
	}
}</span>