挑戰100道編程題（第8道）【Java實現驗證碼功能】

01-需求

用Java實現驗證碼功能。

02-思路

1）編寫一個生成代碼的工具類。

2）在編寫一個登錄頁面（驗證碼通過後，跳轉到該登錄頁面）

3）編寫一個jsp頁面，用於校驗驗證碼。

03-代碼

ImageCodeServlet

package com.eleven;

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

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

@WebServlet("/servlet/ImageCodeServlet")
public class ImageCodeServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		req.setCharacterEncoding("UTF-8");
		resp.setCharacterEncoding("UTF-8");

		/**
		 * 生成帶字符串的文本圖片
		 */
		// 01創建圖片緩存區
		BufferedImage image = new BufferedImage(68, 22, BufferedImage.TYPE_INT_BGR); // 寬、高和圖片類型
		// 02創建繪製環境
		Graphics paint = image.getGraphics();
		Color c = new Color(200, 150, 255);
		// 設置畫筆
		paint.setColor(c);
		// 畫背景
		paint.fillRect(0, 0, 68, 22);

		StringBuffer codes = new StringBuffer();
		// 設置文本
		char[] ch = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890".toCharArray();
		Random r = new Random(); // 隨機數
		int index;
		for (int i = 0; i < 4; i++) {
			index = r.nextInt(ch.length);
			paint.setColor(new Color(r.nextInt(88), r.nextInt(150), r.nextInt(255))); // 設置文本顏色
			paint.drawString(ch[index] + "", (i * 16) + 3, 18);
			codes.append(ch[index]);
		}
		req.getSession().setAttribute("codes", codes);
		//
		// 03輸出圖片
		ImageIO.write(image, "JPG", resp.getOutputStream());
	}

}

LoginServlet

package com.eleven;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/servlet/LoginServlet")
public class LoginServlet extends HttpServlet {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		String codes = req.getSession().getAttribute("codes").toString();
		String mycode = req.getParameter("checkcode");
		resp.setCharacterEncoding("UTF-8");
		req.setCharacterEncoding("UTF-8");
		
		PrintWriter out = resp.getWriter();
		if (mycode.toUpperCase().equals(codes)) {
			out.println("驗證碼輸入正確!");
		} else {
			out.println("驗證碼輸入錯誤!");
		}
		out.flush();
		out.close();
	}
}

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>
<script type="text/javascript">
function reloadcode(){
	var time = new Date().getTime();
	document.getElementById("imagecode").src="servlet/ImageCodeServlet?d="+time;
}


</script>
</head>
<body>
<form action="servlet/LoginServlet" method="get">
	驗證碼：<input type="text" name="checkcode">
	<img alt="驗證碼" src="servlet/ImageCodeServlet" id="imagecode">
	<a href="javascript:reloadcode();">看不清楚</a>
<input type="submit" value="驗證">
</form> 
</body>
</html>