RESTful Java Web Services - Third Edition

Conditional request processing with the Last-Modified HTTP response header

The Last-Modified header field value in HTTP is often used for validating the cached response contents. The Last-Modified entity-header field indicates the date and time at which the entity present in the response body was last modified. A client can use the Last-Modified header field value in combination with the If-Modified-Since or If-Unmodified-Since request headers to perform conditional requests.

The following example illustrates the use of the Last-Modified HTTP header field in the JAX-RS application. The Last-Modified field contains the date when the resource was last changed. When a client requests the same resource next time, it sends the If-Modified-Since ...