這里寫了一個生成驗證碼的demo
前臺可以訪問該servlet頁面顯示驗證碼
驗證碼 后臺存的session名稱為vCode 判斷驗證碼是否正確時可以直接調用
前臺通過
這里你就自己引入jq吧

<img src="ValidateCodeServle" id="src"> <a onclick="code()">看不清楚，換一張</a> <script>function code(){$.("#src").attr({src:codeservlet()});}function codeservlet(){$.post("ValidateCodeServle",,function(data){return data;})} </script> package com.jdbc.util;import java.awt.Color; import java.awt.Font; 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;/*** Servlet implementation class ValidateCodeServle*/ @WebServlet("/ValidateCodeServle") public class ValidateCodeServle extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public ValidateCodeServle() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request, response);}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubresponse.setHeader("Pragma", "No-Cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expries", 0);// 隨機數生成類Random random = new Random();// 定義驗證碼的位數int size = 5;// 定義變量保存生成的驗證碼String vCode = "";char c;// 產生驗證碼for (int i = 0; i < size; i++) {// 產生一個26以內的隨機整數int number = random.nextInt(26);// 如果生成的是偶數，則隨機生成一個數字if (number % 2 == 0) {c = (char) ('0' + (char) ((int) (Math.random() * 10)));// 如果生成的是奇數，則隨機生成一個字母} else {c = (char) ((char) ((int) (Math.random() * 26)) + 'A');}vCode = vCode + c;}// 保存生成的5位驗證碼request.getSession().setAttribute("vCode", vCode);// 驗證碼圖片的生成// 定義圖片的寬度和高度int width = (int) Math.ceil(size * 20);int height = 30;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 獲取圖片的上下文Graphics gr = image.getGraphics();// 設定圖片背景顏色gr.setColor(Color.WHITE);gr.fillRect(0, 0, width, height);// 設定圖片邊框gr.setColor(Color.GRAY);gr.drawRect(0, 0, width - 1, height - 1);// 畫十條干擾線for (int i = 0; i < 5; i++) {int x1 = random.nextInt(width);int y1 = random.nextInt(height);int x2 = random.nextInt(width);int y2 = random.nextInt(height);gr.setColor(randomColor());gr.drawLine(x1, y1, x2, y2);}// 設置字體，畫驗證碼gr.setColor(randomColor());gr.setFont(randomFont());gr.drawString(vCode, 10, 22);// 圖像生效gr.dispose();// 輸出到頁面ImageIO.write(image, "JPEG", response.getOutputStream());}// 生成隨機的顏色private Color randomColor() {int red = r.nextInt(150);int green = r.nextInt(150);int blue = r.nextInt(150);return new Color(red, green, blue);}private String[] fontNames = { "宋體", "華文楷體", "黑體", "微軟雅黑", "楷體_GB2312" };private Random r = new Random();// 生成隨機的字體private Font randomFont() {int index = r.nextInt(fontNames.length);String fontName = fontNames[index];// 生成隨機的字體名稱int style = r.nextInt(4);int size = r.nextInt(3) + 24; // 生成隨機字號, 24 ~ 28return new Font(fontName, style, size);}}

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