Java生成驗證碼並進行驗證
阿新 • • 發佈:2019-01-09
一、實現思路
- 使用BufferedImage用於在記憶體中儲存生成的驗證碼圖片
- 使用Graphics來進行驗證碼圖片的繪製,並將繪製在圖片上的驗證碼存放到session中用於後續驗證
- 最後通過ImageIO將生成的圖片進行輸出
- 通過頁面提交的驗證碼和存放在session中的驗證碼對比來進行校驗
二、生成驗證碼
頁面通過訪問servlet來生成驗證碼,servlet中的程式碼如下:
package org.test;
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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* @author worm0527
* 2016-03-22 23:15:54
* 生成驗證碼
*/
public class ImageServlet extends HttpServlet{
// 圖片高度
private static final int IMG_HEIGHT = 100;
// 圖片寬度
private static final int IMG_WIDTH = 30;
// 驗證碼長度
private static final int CODE_LEN = 4;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// 用於繪製圖片,設定圖片的長寬和圖片型別(RGB)
BufferedImage bi = new BufferedImage(IMG_HEIGHT, IMG_WIDTH, BufferedImage.TYPE_INT_RGB);
// 獲取繪圖工具
Graphics graphics = bi.getGraphics();
graphics.setColor(new Color(100, 230, 200)); // 使用RGB設定背景顏色
graphics.fillRect(0, 0, 100, 30); // 填充矩形區域
// 驗證碼中所使用到的字元
char[] codeChar = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456".toCharArray();
String captcha = ""; // 存放生成的驗證碼
Random random = new Random();
for(int i = 0; i < CODE_LEN; i++) { // 迴圈將每個驗證碼字元繪製到圖片上
int index = random.nextInt(codeChar.length);
// 隨機生成驗證碼顏色
graphics.setColor(new Color(random.nextInt(150), random.nextInt(200), random.nextInt(255)));
// 將一個字元繪製到圖片上,並制定位置(設定x,y座標)
graphics.drawString(codeChar[index] + "", (i * 20) + 15, 20);
captcha += codeChar[index];
}
// 將生成的驗證碼code放入sessoin中
req.getSession().setAttribute("code", captcha);
// 通過ImageIO將圖片輸出
ImageIO.write(bi, "JPG", resp.getOutputStream());
}
}
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三、校驗驗證碼
通過前臺提交的驗證碼與session中資料進行對比來校驗驗證碼,程式碼如下:
package org.test;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CheckCodeServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
// 獲取存放在session中的驗證碼
String code = (String) req.getSession().getAttribute("code");
// 獲取頁面提交的驗證碼
String inputCode = req.getParameter("code");
if(code.toLowerCase().equals(inputCode.toLowerCase())) { // 驗證碼不區分大小寫
// 驗證成功,跳轉到成功頁面
req.getRequestDispatcher("/success.jsp").forward(req, resp);
} else { // 驗證失敗
req.getRequestDispatcher("/fail.jsp").forward(req, resp);
}
}
}
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驗證碼提交頁面html程式碼:
<form action="<%=request.getContextPath() %>/checkCode" method="post">
請輸入驗證碼:<input type="text" name="code">
<input type="submit" value="確定">
</form>
<img alt="驗證碼" id="scode" src="<%=request.getContextPath() %>/getCode" >
<a href="#" onclick="javascript:flushCode();">看不清?</a>
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當生成的驗證碼不清楚時需要重新整理重新生成驗證碼,js程式碼如下:
function flushCode() {
// 每次重新整理的時候獲取當前時間,防止瀏覽器快取重新整理失敗
var time = new Date();
document.getElementById("scode").src = "<%=request.getContextPath()%>/getCode?time=" + time;
}