/**
* Add ETag and Last-Modified cache control headers to the response
*
* @param servletResponse the servlet response
* @param resource the fedora resource
* @param session the session
*/
protected static void addCacheControlHeaders(
final HttpServletResponse servletResponse,
final FedoraResource resource,
final Session session) {
final String txId = TransactionServiceImpl.getCurrentTransactionId(session);
if (txId != null) {
// Do not add caching headers if in a transaction
return;
}
final FedoraResource mutableResource =
resource instanceof NonRdfSourceDescription
? ((NonRdfSourceDescription) resource).getDescribedResource()
: resource;
final EntityTag etag = new EntityTag(mutableResource.getEtagValue());
final Date date = mutableResource.getLastModifiedDate();
if (!etag.getValue().isEmpty()) {
servletResponse.addHeader("ETag", etag.toString());
}
if (date != null) {
servletResponse.addDateHeader("Last-Modified", date.getTime());
}
}
private static void evaluateRequestPreconditions(
final Request request,
final HttpServletResponse servletResponse,
final FedoraResource resource,
final Session session,
final boolean cacheControl) {
final String txId = TransactionServiceImpl.getCurrentTransactionId(session);
if (txId != null) {
// Force cache revalidation if in a transaction
servletResponse.addHeader(CACHE_CONTROL, "must-revalidate");
servletResponse.addHeader(CACHE_CONTROL, "max-age=0");
return;
}
final EntityTag etag = new EntityTag(resource.getEtagValue());
final Date date = resource.getLastModifiedDate();
final Date roundedDate = new Date();
if (date != null) {
roundedDate.setTime(date.getTime() - date.getTime() % 1000);
}
Response.ResponseBuilder builder = request.evaluatePreconditions(etag);
if (builder != null) {
builder = builder.entity("ETag mismatch");
} else {
builder = request.evaluatePreconditions(roundedDate);
if (builder != null) {
builder = builder.entity("Date mismatch");
}
}
if (builder != null && cacheControl) {
final CacheControl cc = new CacheControl();
cc.setMaxAge(0);
cc.setMustRevalidate(true);
// here we are implicitly emitting a 304
// the exception is not an error, it's genuinely
// an exceptional condition
builder = builder.cacheControl(cc).lastModified(date).tag(etag);
}
if (builder != null) {
throw new WebApplicationException(builder.build());
}
}
