很多新手對圖片驗證碼不是很瞭解,今天我們就來看看一個實例吧!
首先,先寫一個動態圖片生成的Servlet類。
如下:
package com.validationCode;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class RandomCode extends HttpServlet {
private static final long serialVersionUID = 1L;
private static int WIDTH = 65;//設置圖片的寬度
private static int HEIGHT = 22;//設置圖片的高度
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {
HttpSession session = request.getSession();
response.setContentType("image/jpeg");
ServletOutputStream sos = response.getOutputStream();
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
char[] rands = generateCheckCode();
drawBackground(g);
drawRands(g, rands);
g.dispose();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ImageIO.write(image, "JPEG", bos);
byte[] buf = bos.toByteArray();
response.setContentLength(buf.length);
sos.write(buf);
bos.close();
sos.close();
session.setAttribute("randomCode", new String(rands));
}
private void drawBackground(Graphics g) {
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, WIDTH, HEIGHT);
for (int i = 0; i < 120; i++) {
int x = (int) (Math.random() * WIDTH);
int y = (int) (Math.random() * HEIGHT);
int red = (int) (Math.random() * 255);
int green = (int) (Math.random() * 255);
int blue = (int) (Math.random() * 255);
g.setColor(new Color(red, green, blue));
g.drawOval(x, y, 1, 0);
}
}
private void drawRands(Graphics g, char[] rands) {
// g.setColor(Color.BLUE);
Random random = new Random();
int red = random.nextInt(110);
int green = random.nextInt(50);
int blue = random.nextInt(50);
g.setColor(new Color(red, green, blue));
g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 18));
g.drawString("" + rands[0], 1, 17);
g.drawString("" + rands[1], 16, 15);
g.drawString("" + rands[2], 31, 18);
g.drawString("" + rands[3], 46, 16);
}
private char[] generateCheckCode() {
String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char[] rands = new char[4];
for (int i = 0; i < 4; i++) {
int rand = (int) (Math.random() * 36);
rands[i] = chars.charAt(rand);
}
return rands;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}
然後保存爲RandomCode.java。
然後進行編譯,生成RandomCode.class文件,放到WEB-INF/classes/com/validationCode目錄下;
然後修改WEB-INF目錄中的web.xml,添加Servlet配置:
<servlet> <servlet-name>RandomCodeServlet</servlet-name> <servlet-class>org.yuanliang.RandomCode</servlet-class> </servlet> <servlet-mapping> <servlet-name>RandomCodeServlet</servlet-name> <url-pattern>/imgcode</url-pattern> </servlet-mapping>
最後,在JSP頁面中加入動態生成的圖片驗證碼.
如: <img src="imgcode"/>
這時新的問題來了,如果用戶看不清楚這個圖片怎麼爲呢?
對了,就是加入刷新功能.
說兩種簡單的方法吧:
1.直接點擊圖片更換驗證碼:
可用JS腳本,添加如下代碼到JSP頁面中:
<script type="text/javascript">
function changeCode()
{
document.getElementById("rc").src="imgcode";
}
</script>
更改驗證圖片導入的代碼:
<img src="imgcode" id="rc" onclick="changeCode()" title="看不清?單擊換一張圖片" />
2.添加文字鏈接,使其更換:
<a href="javascript:changeCode();">看不清?單擊換一張圖片</a>
OK!!!運行JSP頁面,效果出來了。