JAVAWEB中的Reponse動態生成驗證碼輸出到瀏覽器中的大致邏輯以及點選切換驗證碼

阿新 • • 發佈：2021-02-11

多說無益，直接上程式碼

package Request;

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; 

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/responseDemo12")
public class ResponseDemo12 extends HttpServlet {
    int width = 100;
    int height = 50;

    @Override
    protected void doPost(HttpServletRequest req, 
 HttpServletResponse resp) throws ServletException, IOException {
//        1、建立一物件，在記憶體中畫圖（驗證碼的圖片物件）
        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();
        g.setColor(Color.pink);
        g. 
fillRect(0,0,width,height);
//        2.2、話邊框
        g.setColor(Color.blue);
        g.drawRect(0,0,width-1,height-1);

//        2.3  寫驗證碼
        String str = "abcdefghijklmopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
//        建立一個隨機類
        Random random = new Random();

//        獲取字元
        int x = 10;
        for(int i=0;i<4;i++) {
            int index = random.nextInt(str.length());
            String ch = str.charAt(index)+"";
            g.drawString(ch,width/5*(i+1),height/2);
            x+=5;
        }
//        2.4畫干擾線
        for(int i=0;i<10;i++) {
            int point1 = random.nextInt(width);
            int point2 = random.nextInt(width);
            int point3 = random.nextInt(width);
            int point4 = random.nextInt(width);

            g.setColor(Color.green);
            g.drawLine(point1,point2,point3,point4);
        }
        //        3、將圖片輸出到頁面展示
        ImageIO.write(image, "jpg", resp.getOutputStream());
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
}

點選切換，還是直接上程式碼

**注意解決瀏覽器動態快取圖片的問題**

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
    <script>
    /*

               點選超連結或者圖片,換一張
        1、給超連線和圖片繫結單擊事件
        2、重新設定圖片的src屬性值
     */
        window.onload = function () {
        //1、獲取圖片而物件
          var img =   document.getElementById("checkCode");
        //2、給image繫結單擊事
            img.onclick = function () {
                //加事件戳
                var date = new Date().getTime();
                img.src="/responseDemo12?"+date; //解決瀏覽本地快取，圖片不切換
            }

            var change  = document.getElementById("change");
            change.onclick = function () {
                var date = new Date().getTime();
                img.src="/responseDemo12?"+date;
            }
        }

    </script>
<body>
    <img id="checkCode" src="/responseDemo12" />
    <a id="change" href="">看不清換一張</a>
</body>
</html>