三部分內容
1、在登錄頁面生成驗證碼圖片
2、點擊圖片更換新的驗證碼圖片
3、點擊登錄,判定輸入驗證碼與實際驗證碼是否一致
1、如何生成一個驗證碼圖片,放置在登錄頁面?
servlet:
package com.zs.ssh.yzmServlet;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
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;
import javax.servlet.http.HttpSession;
/**
* Servlet implementation class yzmServlet
*/
@WebServlet("/yzmServlet")
public class yzmServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public yzmServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 首先設置瀏覽器不緩存
response.setHeader("cache-control", "no-cache");
response.setHeader("Expire", "-1"); // >0爲緩存
response.setHeader("pragma", "no-cache");
// 存儲正確的驗證碼
String vali_code = "";
String Vali_str = "abcdefghijklmnopqrstuvwsyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";
Color[] colors =
{ Color.BLACK, Color.RED, Color.BLUE };
// 1.創建圖像
int width = 110, height = 40;
int x_offset = 5, y_offset = 28;
BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
// 2.創建畫布
Graphics2D g = img.createGraphics();
// 3.爲畫布添加背景顏色爲亮灰色
g.setColor(Color.LIGHT_GRAY);
g.fillRect(0, 0, width, height);//fillRect是包括矩形框內部
// 4.爲畫布添加邊框
g.setColor(Color.BLUE);
g.drawRect(0, 0, width - 1, height - 1);//drawRect是繪製矩形邊框
// 5.繪製干擾線
for (int i = 0; i < 10; i++)
{
g.setColor(new Color(randNum(0, 255), randNum(0, 255), randNum(0, 255)));
g.drawLine(randNum(0, width), randNum(0, height), randNum(0, width), randNum(0, height));
}
g.setFont(new Font("黑體", Font.BOLD, 20));
for (int i = 0; i < 4; i++)
{
int r = randNum(-180, 180);
String code = Vali_str.charAt(randNum(0, Vali_str.length() - 1)) + "";
g.rotate(r / 180 * Math.PI);
g.setColor(colors[randNum(0, colors.length)]);
g.drawString(code, x_offset + i * 30, y_offset);
g.rotate(-r / 180 * Math.PI);
vali_code += code;
}
//將驗證碼的內容存儲在HttpSession中
HttpSession session = request.getSession();
session.setAttribute("Valicode", vali_code);
// 通過response的輸出流打給瀏覽器
ImageIO.write(img, "jpg", response.getOutputStream());
}
private Random random = new Random();
//隨機生成begin和end之間的一個int值
private int randNum(int begin, int end)
{
return random.nextInt(end - begin) + begin;
}
}
html頁面:
<input type="text" placeholder="用戶名" /><!-- 用戶名 -->
<input type="password" id="password"/><!-- 密碼 -->
<img src="/ZXTM/yzmServlet" οnclick="changeValiImage(this)" /><!-- 驗證碼圖片 -->
<input type="text" placeholder="輸入驗證碼" name="ValiImage" /><!-- 輸入驗證碼文本 -->
<button οnclick="doLogin()" >登錄</button>
2、如何切換驗證圖片?
<!-- 驗證碼圖片點擊切換 -->
<!-- 通過Date來改變每次訪問的url不同 -->
<script type="text/javascript">
function changeValiImage(img){
img.src = "/ZXTM/yzmServlet?time=" + new Date().getTime();
}
</script>
2、如何判定驗證碼的一致性?
在 doLogin() 登錄的方法裏面:
獲取網頁文本信息
再獲取getSession().getAttribute("Valicode")裏面保存的生成的驗證碼信息
String vali_user = getRequest().getParameter("ValiImage");
String vali_sys = getSession().getAttribute("Valicode").toString();