验证码的编写——本质：图片目的：防止恶意表单注册
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验证码的编写——本质：图片目的：防止恶意表单注册
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驗證碼
?? ??? ?1. 本質：圖片
?? ??? ?2. 目的：防止惡意表單注冊
CheckCodeServlet.java
package cn.itcast.web.servlet;import javax.imageio.ImageIO; 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; import java.awt.*; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random;@WebServlet("/checkCodeServlet") public class CheckCodeServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {int width = 100;int height = 50;//1.創建一對象，在內存中圖片(驗證碼圖片對象)BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//2.美化圖片//2.1 填充背景色Graphics g = image.getGraphics();//畫筆對象g.setColor(Color.PINK);//設置畫筆顏色g.fillRect(0,0,width,height);//填充背景色//2.2畫邊框g.setColor(Color.BLUE);g.drawRect(0,0,width - 1,height - 1);String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";//生成隨機角標Random ran = new Random();for (int i = 1; i <= 4; i++) {int index = ran.nextInt(str.length());//獲取字符char ch = str.charAt(index);//隨機字符//2.3寫驗證碼g.drawString(ch+"",width/5*i,height/2);}//2.4畫干擾線g.setColor(Color.GREEN);//隨機生成坐標點for (int i = 0; i < 10; i++) {int x1 = ran.nextInt(width);int x2 = ran.nextInt(width);int y1 = ran.nextInt(height);int y2 = ran.nextInt(height);g.drawLine(x1,y1,x2,y2);}//3.將圖片輸出到頁面展示ImageIO.write(image,"jpg",response.getOutputStream());}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request,response);} }register.html
<!DOCTYPE html> <html lang="en"> <head><meta charset="UTF-8"><title>Title</title><script>/*分析：點擊超鏈接或者圖片，需要換一張1.給超鏈接和圖片綁定單擊事件2.重新設置圖片的src屬性值*/window.onload = function(){//1.獲取圖片對象var img = document.getElementById("checkCode");//2.綁定單擊事件img.onclick = function(){//加時間戳 加上時間戳的原因是因為瀏覽器的緩存問題var date = new Date().getTime();img.src = "/day15/checkCodeServlet?"+date;}var change=document.getElementById("change");change.onclick = function(){//加時間戳 加上時間戳的原因是因為瀏覽器的緩存問題var date = new Date().getTime();img.src = "/day15/checkCodeServlet?"+date;}}</script> </head> <body><img id="checkCode" src="/day15/checkCodeServlet" /><a id="change" href="">看不清換一張？</a> </body> </html>總結
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