code.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>code.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">
$(function() {
init();
$("[type='button']").click(function() {
$.post("servlet/CheckCode",{},function(data) {
//注意这里src的写法，data是经过base64编码后的内容
$("img").attr("src","data:image/jpeg;base64,"+data);
});
});
});
function init() {
$.post("servlet/CheckCode",{},function(data) {
//其实在第一次运行的时候是可以直接将图片的二进制作为Image的src进行显示的，但是因为后台统一返回的是
//经过base64编码过后的内容，所以这里初始显示的时候也是利用base64的方法
$("img").attr("src","data:image/jpeg;base64,"+data);
});
}
</script>
</head>
<body>
<img alt="" width=100 >
<input type="button" value="换一张"/>
</body>
</html>
Servlet：
mport java.io.IOException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import sun.misc.BASE64Encoder;
import com.tiantian.ext.util.Util;
public class CheckCode extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//直接返回字节流给img标签的src是可以的，如<img src="servlet/CheckCode">，但在之后进行切换的时候
//使用ajax请求，如果仅仅返回图片的二进制然后把它传给img的src是不能的，目前的方法是把图片的二进制进行base64编码，
//然后在页面上以下列方式进行显示，<img src="data:image/jpeg;base64,result">,其中的result是经过
//base64编码后的内容，这样就可以使用后台直接利用图片的二进制进行图片的显示了
response.setContentType("image/jpeg;charset=utf-8");
response.addHeader("pragma", "no-cache");
response.addHeader("Cache-Control", "no-cache");
StringBuffer buffer = new StringBuffer();
for (int i=0;i<4;i++)
buffer.append(new Random().nextInt(9));
String code = buffer.toString();
byte[] bytes = Util.geneCheckCode(code).toByteArray();
BASE64Encoder encoder = new BASE64Encoder();
//使用base64进行转码，否则在页面不能直接显示，至少目前我还没有发现方法，可以直接将图片的字节流使用ajax的方法在页面
//上进行显示
String result = encoder.encode(bytes);
response.getWriter().write(result);
}
}
Util类：
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.Properties;
import java.util.Random;
import javax.imageio.ImageIO;
import com.google.code.kaptcha.impl.DefaultKaptcha;
import com.google.code.kaptcha.util.Config;
public class Util {
private static DefaultKaptcha kaptcha = new DefaultKaptcha();
//初始化Kaptcha
static {
kaptcha.setConfig(new Config(new Properties()));
}
/**
* 利用kaptcha的实现
* @param code
* @return
* @throws IOException
*/
public static ByteArrayOutputStream geneCheckCode(String code) throws IOException {
BufferedImage bufferedImage = kaptcha.createImage(code);
ByteArrayOutputStream out = new ByteArrayOutputStream();
ImageIO.write(bufferedImage, "jpg", out);
return out;
}
/**
* 自己的实现
* @param text
* @return
* @throws IOException
*/
public static ByteArrayOutputStream gene(String text) throws IOException {
char chars[] = text.toCharArray();
BufferedImage image = new BufferedImage(200, 50, BufferedImage.TYPE_INT_BGR);
Graphics graphics = image.getGraphics();
graphics.setColor(Color.red);
for (int i=0;i<chars.length;i++) {
graphics.setFont(new Font("宋体", Font.BOLD, 35+new Random().nextInt(10)));
graphics.drawChars(new char[] {chars[i]}, 0, 1, 45*i+10, 40);
}
graphics.setColor(new Color(255, 200, 200));
for (int i=0;i<17;i++) {
graphics.drawLine(i*12, 0, i*12, 50);
graphics.drawLine(0, i*3, 200, i*3);
}
ByteArrayOutputStream out = new ByteArrayOutputStream();
ImageIO.write(image, "jpg", out);
return out;
}
}
