Responses in Detail
When the web server receives the request, it looks at the URI and decides, based on configuration information, how to handle it. It may handle it internally by simply reading an HTML file from the filesystem, or it can forward the request to some component that is responsible for the resource corresponding to the URI. This can be a program that uses database information, for instance, to dynamically generate an appropriate response. To the browser it makes no difference how the request is handled; all it cares about is getting a response.
The response message looks similar to the request message. It consists of three things: a status line, response headers, and an optional response body. Here’s an example:
HTTP/1.1 200 OK
Last-Modified: Mon, 20 Dec 2002 23:26:42 GMT
Date: Tue, 11 Jan 2003 20:52:40 GMT
Status: 200
Content-Type: text/html
Servlet-Engine: Tomcat Web Server/5.0
Content-Length: 59
<html>
<body>
<h1>Hello World!</h1>
</body>
</html>The status line starts with the name of the protocol, followed by a
status code and a short description of the status code. Here the
status code is 200, meaning the request was executed successfully.
The response message has headers just like the request message. In
this example, the
Last-Modified
header gives the date and time for when the resource was last modified. The browser can use this information as a timestamp in a local cache; the next time the user asks for this resource, he can ask the server to send it only ...
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