如何在 servlet 上设置内容类型 [英] How to set the content type on the servlet

问题描述

我正在使用一个简单的 servlet，它将数据库中的文档内容作为字节数组发回.我想设置一个内容 type 以便在通过 doGet() 调用检索时具有适当的扩展名.

我确实将文档的类型作为元数据存储在数据库中(例如 png、gif、png、xls、docx ...).

1. 我应该设置什么内容类型才能保留文件扩展名?
2. 下载的文件名为doc"，如何在 servlet 上为正在下载的数据设置文件名.

解决方案

我应该设置什么内容类型才能保留文件扩展名?

使用ServletContext#getMimeType()根据文件名获取mime类型.

String mimeType = getServletContext().getMimeType(filename);

servletcontainer 通常已经在它自己的 web.xml 中提供了默认的 MIME 类型映射.如果你想覆盖或添加一些其他的，那么把它作为新的 mime 映射放在 webapp 的 web.xml 中.例如

<extension>docx</extension><mime-type>application/vnd.openxmlformats-officedocument.wordprocessingml.document</mime-type></mime-mapping><mime-mapping><扩展名>xlsx</扩展名><mime-type>application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</mime-type></mime-mapping>

最后将其设置为Content-Type响应头:

response.setContentType(mimeType);

<小时><块引用>

下载的文件名为doc"，如何在 servlet 上为正在下载的数据设置文件名.

将其添加到 servlet URL，因为某些浏览器(如 MSIE)会忽略内容处置的 filename 属性.

下载文件名.ext

如果servlet映射到/download/*的URL模式，则可以通过如下方式获取

String filename = request.getPathInfo().substring(1);

最后将其设置在 Content-Disposition 标头中，以使普通浏览器满意:

response.setHeader("Content-Disposition", "attachment; filename="" + filename + """);

如果您不在 DB 中存储文件名，而是将 ID 或其他内容存储在数据库中，则将其用作文件名.

<a href="download/${file.id}.${file.ext}">down​​load ${file.id}.${file.ext}</a>

然后在servlet中

String filename = request.getPathInfo().substring(1);String id = filename.split("\.")[0];//根据 id 从 DB 获取.

I am using a simple servlet which sends back document contents from the database as a byte array. I would like to set a content type so that it has an appropriate extension while it is being retrieved via a doGet() call.

I do have the type of the document stored as a metadata in the database (e.g. png, gif, png, xls, docx ...).

1. What should I set as the content type so that it retains the file extension?
2. The file gets downloaded with a name of "doc", how do I set the filename on the servlet for the data being downloaded.

解决方案

What should I set as the content type so that it retains the file extension?

Use ServletContext#getMimeType() to get the mime type based on the file name.

String mimeType = getServletContext().getMimeType(filename);

The servletcontainer usually already provides a default mime type mapping in its own web.xml. If you want to overridde or add some other, then put it as new mime mappings in webapp's web.xml. E.g.

<mime-mapping>
    <extension>docx</extension>
    <mime-type>application/vnd.openxmlformats-officedocument.wordprocessingml.document</mime-type>
</mime-mapping>
<mime-mapping>
    <extension>xlsx</extension>
    <mime-type>application/vnd.openxmlformats-officedocument.spreadsheetml.sheet</mime-type>
</mime-mapping>

Finally set it as the Content-Type response header:

response.setContentType(mimeType);

---

The file gets downloaded with a name of "doc", how do I set the filename on the servlet for the data being downloaded.

Add it to the servlet URL because some browsers like MSIE ignores the filename attribute of the content disposition.

<a href="download/filename.ext">download filename.ext</a>

If the servlet is mapped on an URL pattern of /download/*, then you can obtain it as follows

String filename = request.getPathInfo().substring(1);

Finally set it in the Content-Disposition header as well to make normal browsers happy:

response.setHeader("Content-Disposition", "attachment; filename="" + filename + """);

If you don't store filenames in DB but rather IDs or something, then use it as filename instead.

<a href="download/${file.id}.${file.ext}">download ${file.id}.${file.ext}</a>

And then in the servlet

String filename = request.getPathInfo().substring(1);
String id = filename.split("\.")[0];
// Obtain from DB based on id.

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