本文介绍了一种通过Base64编码处理Cookie中的二进制数据的方法，具体展示了如何将图片文件编码为Base64字符串存储在Cookie中，并在客户端解析还原该图片。
Cookie不仅可以使用ASCII字符与Unicode字符，还可以使用二进制数据。
例如数字证书，提高安全度。使用二进制数据时也需要进行编码
保存二进制数据内容，不实用。Cookie内容过多，影响速度。应少而精
base64.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" isErrorPage="true"%>
<jsp:directive.page import="java.io.File"/>
<jsp:directive.page import="java.io.InputStream"/>
<jsp:directive.page import="sun.misc.BASE64Encoder"/>
<%
File file = new File(this.getServletContext()
.getRealPath("cookie.gif"));
byte[] binary = newbyte[(int)file.length()];
//从图片文件读取二进制数据
InputStream is = this.getServletContext()
.getResourceAsStream(file.getName());
is.read(binary);
is.close();
String content = BASE64Encoder.class.newInstance().encode(binary);
Cookie cookie = new Cookie("file",content);
response.addCookie(cookie); //将二进制数据发送客户端
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
从Cookie中获取到的二进制图片：<img src="base64_decode.jsp"/><br/>
<textarea id="cookieArea" style="width:500;height:200px;">
</textarea>
<script type="text/javascript">
cookieArea.value = document.cookie;
</script>
</body>
</html>
base64_decode.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" isErrorPage="true"%>
<jsp:directive.page import="sun.misc.BASE64Decoder"/>
<%
out.clear();
for(Cookie cookie:request.getCookies()){
if(cookie.getName().equals("file")){
byte[] binary = BASE64Decoder.class.newInstance()
.decodeBuffer(cookie.getValue().replace(" ",""));
response.setHeader("Content-Type","image/gif");
response.setHeader("Content-Disposition",
"inline;filename=cookie.gif");
response.setHeader("Connection","close");
response.setContentLength(binary.length);
response.getOutputStream().write(binary);
response.getOutputStream().flush();
response.getOutputStream().close();
return;
}
}
%>
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