URL：仅获取最后修改时间（无内容）

Question

有没有办法使用 HttpConnection 只获取 Last Modified header？

当我使用这段代码时：

HttpURLConnection httpCon = (HttpURLConnection) url.openConnection();
long lastModified = httpCon.getLastModified();

在网络服务器的日志文件中，我看到：

a.b.c.d - - [26/Dec/2015:10:25:50 +0100] "GET /file.txt HTTP/1.1" 200 484 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:43.0) Gecko/20100101 Firefox/43.0"

如果我理解正确，GET 请求也会获取全部内容。是否有可能执行 HEAD 请求以仅检索 header？

Answer 1

您可以设置HTTP方法，见HttpURLConnection:

Set the method for the URL request, one of:

GET

POST

HEAD

OPTIONS

PUT

DELETE

TRACE

are legal, subject to protocol restrictions. The default method is GET.

示例：

HttpURLConnection httpUrlConnection = (HttpURLConnection) url.openConnection();
httpUrlConnection.setRequestMethod("HEAD");
long lastModified = httpUrlConnection.getLastModified();

URL：仅获取最后修改时间（无内容）

URL: fetch Last Modified only (without content)

java

httpconnection