Content-Disposition 属性是作为对下载文件的一个标识字段，在rfc2616 http://www.rfc-editor.org/rfc/rfc2616.pdf 章节19.5 Additional Features中

有介绍，具体介绍请看 http://www.rfc-editor.org/rfc/rfc1806.txt

字段介绍如下：

disposition := "Content-Disposition" ":"  
               disposition-type  
               *(";" disposition-parm)  
disposition-type := "inline"  
                  / "attachment"  
                  / extension-token  
                  ; values are not case-sensitive  
disposition-parm := filename-parm / parameter  
filename-parm := "filename" "=" value;  

Content-Disposition属性有两种类型：inline 和 attachment inline ：将文件内容直接显示在页面 attachment：弹出对话框让用户下载具体例子：

Content-Type: image/jpeg  
Content-Disposition: inline;filename=hello.jpg  
Content-Description: just a small picture of me  

在页面内打开代码：

File file = new File("rfc1806.txt");  
String filename = file.getName();  
response.setHeader("Content-Type","text/plain");  
response.addHeader("Content-Disposition","inline;filename=" + new String(filename.getBytes(),"utf-8"));  
response.addHeader("Content-Length","" + file.length());  

弹出保存框代码：

File file = new File("rfc1806.txt");  
String filename = file.getName();  
response.setHeader("Content-Type","text/plain");  
response.addHeader("Content-Disposition","attachment;filename=" + new String(filename.getBytes(),"utf-8"));  
response.addHeader("Content-Length","" + file.length());