<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;">

</span>

<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>