I guess the question is, why would different routes split over different bundles want to write over the same header/property? What's the case here? Surely it cannot be just to prevent accidents by developers because what would be their reason to write over that header?
I think it is better to agree on a naming and some sort of other convention and stick to that because I don't think there is a way to to make a header immutable. I guess an ugly solution would be to save the header in a map and give the key name something very unique. On Tue, Jul 5, 2016 at 10:48 PM, Matt Sicker [via Camel] < ml-node+s465427n578481...@n5.nabble.com> wrote: > Please let me know if you think of anything! > > On 5 July 2016 at 15:16, Brad Johnson <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=0>> wrote: > > > I certainly understand the impulse and think it is spot on but can't > think > > of how to do it with headers. Claim checks might work but they are > really > > for reducing overhead of data and not for locking like that but that > might > > be a viable solution depending on the exact problem. > > > > Thanks Matt, this is going to be stuck in my head now. I'll probably > dream > > of an answer of some sort tonight. > > > > Brad > > > > On Tue, Jul 5, 2016 at 3:02 PM, Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=1>> wrote: > > > > > My use case is basically to help prevent bugs where a header or > exchange > > > property gets modified. Some of my routes in question branch out into > > > several different bundles, and it is difficult to enforce contracts > that > > > way amongst several developers with varying levels of Camel expertise. > > > Similar to how one might use final variables to prevent people from > > > reassigning them, this could be a final header that prevents people > from > > > reusing them for things. > > > > > > On 5 July 2016 at 14:22, Brad Johnson <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=2>> > > > wrote: > > > > > > > That's what I figured. I'd have to look at the Map implementation > of > > the > > > > exchange but as far as I know there isn't a way to make it a write > once > > > > only operation. It's just a map of some sort. There might be a way > to > > > do > > > > it with transactions but I'm not an expert there. I generally use > > > headers > > > > but in reality should probably be using exchange properties more > often. > > > > > > > > > > > > > > > > > > http://stackoverflow.com/questions/10330998/passing-values-between-processors-in-apache-camel > > > > > > > > Almost any mechanism I can think of off the top of my head could be > > > > subverted by someone who wanted to or who didn't understand that the > > > value > > > > associated with the bean shouldn't be modified. For example, you > could > > > > create a bean that you associate with your header that stores data > but > > > also > > > > returns a UUID. That UUID could be stored in another header and > > sometime > > > > later in the routes you could verify that the bean stored under your > > key > > > > returns the same UUID as the header indicates. But that wouldn't > stop > > > > someone from changing the bean stored to the key and it wouldn't > > prevent > > > > them from updating the UUID to a new bean they might create. > > > > > > > > On Tue, Jul 5, 2016 at 1:49 PM, Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=3>> wrote: > > > > > > > > > I'm thinking of an idea to prevent a header from being modified by > > > other > > > > > parts of the route. A sort of contract if you will. > > > > > > > > > > On 5 July 2016 at 13:01, Brad Johnson <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=4>> > > > > > wrote: > > > > > > > > > > > Is there another part of your process that is specifically > changing > > > the > > > > > > header or are you more concerned about it being consistently > there > > > > across > > > > > > routes? Nothing will change it automatically if it is your > header. > > > I > > > > > > don't remember the actual implementation but conceptually it is > > just > > > a > > > > > > hastable/map with key/values. If you set header with some > specific > > > key > > > > > > then nothing else will change it. > > > > > > > > > > > > As an example, I use a camel splitter and then set a header with > > the > > > > > > splitter index so that I can use it in another route later to > > > > reassemble > > > > > > with the resequencer. > > > > > > > > > > > > <split> > > > > > > <simple>${body}</simple> > > > > > > <setHeader headerName="seqnum"> > > > > > > <simple>exchangeProperty.CamelSplitIndex</simple> > > > > > > </setHeader> > > > > > > ... > > > > > > > > > > > > The "seqnum" is just a key that I'm defining. I could obviously > > call > > > > it > > > > > > anything "sequenceNumber" or whatever but when I access it later > > that > > > > > > header is available on the exchange. If I explicitly change what > > the > > > > map > > > > > is > > > > > > storing for "seqnum" then it will be different because I can't > make > > > the > > > > > > header map itself immutable. > > > > > > > > > > > > > > > > > > On Tue, Jul 5, 2016 at 10:33 AM, Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=5>> > > > wrote: > > > > > > > > > > > > > As in once I set the header, nothing can change the header > during > > > the > > > > > > > lifecycle of the message during a route. Same for an exchange > > > > property. > > > > > > > > > > > > > > -- > > > > > > > Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=6>> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=7>> > > > > > > > > > > > > > > > > > > > > > -- > > > Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=8>> > > > > > > > > > -- > Matt Sicker <[hidden email] > <http:///user/SendEmail.jtp?type=node&node=5784811&i=9>> > > > ------------------------------ > If you reply to this email, your message will be added to the discussion > below: > > http://camel.465427.n5.nabble.com/Is-it-possible-to-make-a-message-header-or-property-immutable-tp5784800p5784811.html > To start a new topic under Camel - Users, email > ml-node+s465427n465428...@n5.nabble.com > To unsubscribe from Camel - Users, click here > <http://camel.465427.n5.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=465428&code=c291Y2lhbmNlLmVxZGFtLnJhc2h0aUBnbWFpbC5jb218NDY1NDI4fDE1MzI5MTE2NTY=> > . > NAML > <http://camel.465427.n5.nabble.com/template/NamlServlet.jtp?macro=macro_viewer&id=instant_html%21nabble%3Aemail.naml&base=nabble.naml.namespaces.BasicNamespace-nabble.view.web.template.NabbleNamespace-nabble.view.web.template.NodeNamespace&breadcrumbs=notify_subscribers%21nabble%3Aemail.naml-instant_emails%21nabble%3Aemail.naml-send_instant_email%21nabble%3Aemail.naml> > -- View this message in context: http://camel.465427.n5.nabble.com/Is-it-possible-to-make-a-message-header-or-property-immutable-tp5784800p5784812.html Sent from the Camel - Users mailing list archive at Nabble.com.
