[英]How to download attachment file from JSP
I want to know how can I download any file from JSP page based on content disposition as an attachment from mail server. 我想知道如何基于邮件服务器的附件内容从JSP页面下载任何文件。
I want to create a link on JSP page, and by clicking on that link user can download file from mail server. 我想在JSP页面上创建一个链接,然后通过单击该链接,用户可以从邮件服务器下载文件。 The link should be for content dispostion's attachment type. 该链接应用于内容伪装的附件类型。 How can I do that in JSP? 如何在JSP中做到这一点?
Don't use a JSP for this, it's recipe for trouble when using it to stream binary files, because all whitespace outside the <% %>
tags will be printed to the response as well which would only corrupt binary content. 请勿为此使用JSP,因为使用JSP来流二进制文件时会麻烦,因为<% %>
标记之外的所有空格也会被打印到响应中,这只会破坏二进制内容。 All you need to do is to just place a HTML link like <a href="fileservlet/file.ext">
in the JSP and use a servlet class to do all the processing and streaming task. 您需要做的就是在JSP中放置一个<a href="fileservlet/file.ext">
类的HTML链接,并使用servlet类来完成所有处理和流传输任务。 To set a response header, just use HttpServletResponse#setHeader()
. 要设置响应头,只需使用HttpServletResponse#setHeader()
。
response.setHeader("Content-Disposition", "attachment;filename=name.ext");
You can find here a basic servlet example which does exactly this: FileServlet
. 您可以在此处找到一个基本的servlet示例,该示例正是这样做的: FileServlet
。
URL url = new URL("http://localhost:8080/Works/images/abt.jpg");
//for image
response.setContentType("image/jpeg");
response.setHeader("Content-Disposition", "attachment; filename=icon" + ".jpg");
//for pdf
//response.setContentType("application/pdf");
//response.setHeader("Content-Disposition", "attachment; filename=report" + ".pdf");
//for excel sheet
// URL url = new URL("http://localhost:8080/Works/images/address.xls");
//response.setContentType("application/vnd.ms-excel");
//response.setHeader("Content-disposition", "attachment;filename=myExcel.xls");
URLConnection connection = url.openConnection();
InputStream stream = connection.getInputStream();
BufferedOutputStream outs = new BufferedOutputStream(response.getOutputStream());
int len;
byte[] buf = new byte[1024];
while ((len = stream.read(buf)) > 0) {
outs.write(buf, 0, len);
}
outs.close();
I suggest you break this question down a bit. 我建议您将这个问题分解一下。
Do you know how to access the attachments from within a regular java program? 您知道如何从常规Java程序中访问附件吗? How to interface with the mail-server etc? 如何与邮件服务器等接口? If you know that, it should be an easy exercise to provide the attachment in a downloadable format through jsp. 如果您知道这一点,那么通过jsp以可下载的格式提供附件应该是一个容易的练习。 Although, I would strongly recommend you to do a regular servlet, since you would probably not have much use of the extra machinery around jsp. 虽然,我强烈建议您执行常规的servlet,因为您可能不太会使用jsp周围的额外机器。
Just make sure you set the content type according to what's being downloaded: 只需确保根据下载的内容设置内容类型即可:
In jsp: <%@page contentType="image/png" %>
在jsp中: <%@page contentType="image/png" %>
In a servelt: response.setContentType("image/png");
在服务中: response.setContentType("image/png");
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