How to get the last update time of the webpage? ? ? ?

hyysios

System.out.println(new Date(con.getDate()));

tellyou

In the agreement, Last-modified is indeed SHOULD level
HTTP/1.1 servers SHOULD send Last-Modified whenever feasible.

Date should be obtained forever, because according to the agreement

Origin servers MUST include a Date header field in all responses, unless
1 When the status code 100 (continue) or 101 (switch protocol) is returned, MAY include a Date header field
2 When the server processes the request response, an error occurs, such as when the status code 500 (internal error) or 503 (service unavailable) is returned
3 The server does not have a reliable clock (???)

However, this and Last-modified required by the original poster belong to two concepts.
Date is actually when the response was output, and Last-modified has more meaning. For static files, it refers to the last update time of the files saved by the system

tellyou

It seems that there is no particularly good solution, the host can decide the last update time according to the priority below

1 Last-modified
2 Date
3 Client system time

zitong1129

Finally add the following Script in the net surface:
...
<script type="javascript/text">
<!-- hide script from old browsers
    document.write("Last Modified:" + document.lastModified)
    // end hiding contents
-->
</script>
</BODY></HTML>

tellyou

js document.lastModified can only get the time of this page/or other pages of this site, it can't do anything about cross-domain, and lz seems to need to run on the server side