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dotnet distributed apps
group:Collecting and propogating Validation Errors and Warnings in the Business Layer and Data Layer
dotnet distributed apps:
of information performed in many layers. Most of the validation will be repeated in both the UI and business layers as the code is structured to also expose functionality as a web service. More advanced validation will be done in both the business layer and data layer e.g. validating groups of related properties or related information in rows of data When validating the information for 'anticipated' problems (errors and warnings), I want to collect all of the various errors/warnings and report them back to the UI as some sort of collection. Ideally, I would prefer not to pass the collection between methods so was looking at possibly using a singleton but I would have to somehow isolate the collection per user's session since the app is 'mostly' stateless. I have searched the net and found many great articles on Exception Management but nothing detailed on validation. Can anyone recommend an approach or point me to some articles? TIA Alan
Hello Alan,
If you don't want pass the exceptions between methods, another way may be MSMQ. Your web service can put the exception information in MSMQ, and client UI receives them. I suggest you may take a look at LOGGING Application Block, it support log information in MSMQ: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html /logging.asp?frame=true hope this help, Luke
Hi Luke,
Thanks for the reply. Maybe I didnt explain myself properly. I am not talking about exceptions as I am already using the application blocks for these. I am talking about validation messages (errors and warnings). These are expected errors where usually, if one occurs, you want to collect it and continue, collecting all of the errors (throughout the layers) until the processing ends. At the end, the UI reports all of the messages so the user can take action. Exceptions are different because they stop processing (unless they are handled) as a result of an exceptional circumstance Thanks Alan [quoted text, click to view] "[MSFT]" <lukezhan@online.microsoft.com> wrote in message news:J59uFsxkFHA.3120@TK2MSFTNGXA01.phx.gbl... > Hello Alan, > > If you don't want pass the exceptions between methods, another way may be > MSMQ. Your web service can put the exception information in MSMQ, and > client UI receives them. I suggest you may take a look at LOGGING > Application Block, it support log information in MSMQ: > > http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html > /logging.asp?frame=true > > hope this help, > > Luke > > > >
Thanks Peter, but I am not talking about exceptions. I am talking about
non-trivial validation errors which are 'expected'. e.g. data was incorrectly entered with validation rules performed via a stored procedure detecting the 'error' Alan [quoted text, click to view] "peter" <apvx95@dsl.pipex.com> wrote in message
news:42e912b1$0$334$cc9e4d1f@news.dial.pipex.com... > Hi Alan, > > I set the Exception's Message property by appending to what's already > there, and then re-throw the exception. > > HTH > > Peter > > Alan Fisher wrote: >> Hi Luke, >> >> Thanks for the reply. Maybe I didnt explain myself properly. I am not >> talking about exceptions as I am already using the application blocks for >> these. I am talking about validation messages (errors and warnings). >> These are expected errors where usually, if one occurs, you want to >> collect it and continue, collecting all of the errors (throughout the >> layers) until the processing ends. At the end, the UI reports all of the >> messages so the user can take action. >> >> Exceptions are different because they stop processing (unless they are >> handled) as a result of an exceptional circumstance >> >> Thanks >> Alan >> "[MSFT]" <lukezhan@online.microsoft.com> wrote in message >> news:J59uFsxkFHA.3120@TK2MSFTNGXA01.phx.gbl... >> >>>Hello Alan, >>> >>>If you don't want pass the exceptions between methods, another way may be >>>MSMQ. Your web service can put the exception information in MSMQ, and >>>client UI receives them. I suggest you may take a look at LOGGING >>>Application Block, it support log information in MSMQ: >>> >>>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html >>>/logging.asp?frame=true >>> >>>hope this help, >>> >>>Luke >>> >>> >>> >>> >> >>
Hi Alan,
I think this won't conflict with my suggestion. When your web service find an error/warning, it can create some log information and post them to MSMQ, then continue to handle the information. It won't stop the processs. When it finished and returned to clients, clients can receive all logged infornmation from MSMQ. Luke
Hi Alan,
I set the Exception's Message property by appending to what's already there, and then re-throw the exception. HTH Peter [quoted text, click to view] Alan Fisher wrote:
> Hi Luke, > > Thanks for the reply. Maybe I didnt explain myself properly. I am not > talking about exceptions as I am already using the application blocks for > these. I am talking about validation messages (errors and warnings). These > are expected errors where usually, if one occurs, you want to collect it and > continue, collecting all of the errors (throughout the layers) until the > processing ends. At the end, the UI reports all of the messages so the user > can take action. > > Exceptions are different because they stop processing (unless they are > handled) as a result of an exceptional circumstance > > Thanks > Alan > "[MSFT]" <lukezhan@online.microsoft.com> wrote in message > news:J59uFsxkFHA.3120@TK2MSFTNGXA01.phx.gbl... > >>Hello Alan, >> >>If you don't want pass the exceptions between methods, another way may be >>MSMQ. Your web service can put the exception information in MSMQ, and >>client UI receives them. I suggest you may take a look at LOGGING >>Application Block, it support log information in MSMQ: >> >>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html >>/logging.asp?frame=true >> >>hope this help, >> >>Luke >> >> >> >> > >
A couple of possibilities come to mind:
A) Depending on how you pass data around between your layers, hang the error collection off the data. DataSet already provides places to store errors, and also a generic mechanism to hang other objects onto the DataSet. B) Use thread local storage for your 'singleton'. In the outermost call you clear the errors collection at the start, and return the collection to the remote caller when done. This depends on all your methods for a single request being called on the same thread - if you are using something that may get called on a different thread, then it gets more complex. For more discussion of some of this, see the Registry pattern in Martin Fowler's book: http://martinfowler.com/eaaCatalog/registry.html HTH -------- Nigel Norris [quoted text, click to view] "Alan Fisher" <Gobba@newsgroup.nospam> wrote in message news:ezii4awkFHA.2852@TK2MSFTNGP14.phx.gbl... >I am building a stateless distributed web application which has validation >of information performed in many layers. Most of the validation will be >repeated in both the UI and business layers as the code is structured to >also expose functionality as a web service. More advanced validation will >be done in both the business layer and data layer e.g. validating groups of >related properties or related information in rows of data > > When validating the information for 'anticipated' problems (errors and > warnings), I want to collect all of the various errors/warnings and report > them back to the UI as some sort of collection. Ideally, I would prefer > not to pass the collection between methods so was looking at possibly > using a singleton but I would have to somehow isolate the collection per > user's session since the app is 'mostly' stateless. > > I have searched the net and found many great articles on Exception > Management but nothing detailed on validation. Can anyone recommend an > approach or point me to some articles? > > TIA > Alan > > > > >
Alan,
Rockford Lhotka's CSLA .NET uses a "Broken Rules" collection that represents each of the validation failures for a domain object. http://www.lhotka.net/ Unfortunately his site appears to be down temporarily... Hope this helps Jay [quoted text, click to view] "Alan Fisher" <Gobba@newsgroup.nospam> wrote in message |I am building a stateless distributed web application which has validationnews:ezii4awkFHA.2852@TK2MSFTNGP14.phx.gbl... | of information performed in many layers. Most of the validation will be | repeated in both the UI and business layers as the code is structured to | also expose functionality as a web service. More advanced validation will be | done in both the business layer and data layer e.g. validating groups of | related properties or related information in rows of data | | When validating the information for 'anticipated' problems (errors and | warnings), I want to collect all of the various errors/warnings and report | them back to the UI as some sort of collection. Ideally, I would prefer not | to pass the collection between methods so was looking at possibly using a | singleton but I would have to somehow isolate the collection per user's | session since the app is 'mostly' stateless. | | I have searched the net and found many great articles on Exception | Management but nothing detailed on validation. Can anyone recommend an | approach or point me to some articles? | | TIA | Alan | | | | |
OK. I can only offer our experience, I'm afraid - so I don't know how
relevant it is. For business rules (i.e. is the input valid for our business? - e.g. a student number must be 8 digits, etc), we construct a remote validation class that lives on the application server. It has methods to validate all data and process all business rules. When a user moves from one page to another of the application, we apply the rules to the data in the page/form in order to decided whether the user should be allowed to progress, or carry out the requested action. Normally, we would return on the first failure and report that, but I can see there would be cases for applying all the rules and reporting all the failures. We would do this by calling all the appropriate methods in the remote validation object, building up a message to return as failures occur. You could either return a null string on success, with the error message (as built) as the return value on failure or, as we prefer, to return true on success and throw an exception with the error message assigned to the exception's message property, on failure. This latter means that you must configure remoting to return error messages from remote exceptions, of course, in your config file. HTH Peter [quoted text, click to view] Alan Fisher wrote:
> Thanks Peter, but I am not talking about exceptions. I am talking about > non-trivial validation errors which are 'expected'. e.g. data was > incorrectly entered with validation rules performed via a stored procedure > detecting the 'error' > > Alan > > "peter" <apvx95@dsl.pipex.com> wrote in message > news:42e912b1$0$334$cc9e4d1f@news.dial.pipex.com... > >>Hi Alan, >> >>I set the Exception's Message property by appending to what's already >>there, and then re-throw the exception. >> >>HTH >> >>Peter >> >>Alan Fisher wrote: >> >>>Hi Luke, >>> >>>Thanks for the reply. Maybe I didnt explain myself properly. I am not >>>talking about exceptions as I am already using the application blocks for >>>these. I am talking about validation messages (errors and warnings). >>>These are expected errors where usually, if one occurs, you want to >>>collect it and continue, collecting all of the errors (throughout the >>>layers) until the processing ends. At the end, the UI reports all of the >>>messages so the user can take action. >>> >>>Exceptions are different because they stop processing (unless they are >>>handled) as a result of an exceptional circumstance >>> >>>Thanks >>>Alan >>>"[MSFT]" <lukezhan@online.microsoft.com> wrote in message >>>news:J59uFsxkFHA.3120@TK2MSFTNGXA01.phx.gbl... >>> >>> >>>>Hello Alan, >>>> >>>>If you don't want pass the exceptions between methods, another way may be >>>>MSMQ. Your web service can put the exception information in MSMQ, and >>>>client UI receives them. I suggest you may take a look at LOGGING >>>>Application Block, it support log information in MSMQ: >>>> >>>>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag2/html >>>>/logging.asp?frame=true >>>> >>>>hope this help, >>>> >>>>Luke >>>> >>>> >>>> >>>> >>> >>>
I'm having the same problem. I have created a class ValidationResult which
looks like: class ValidationResult { ValidationStatus Status; ValidationItemCollection Items; } The ValidationItem is defined as below: class ValidationItem { ValidationStatus Staus; string Code; // Error code usually, but can be a warning, info or sth else string Message; } ValidationStatus is an enumeration which for the moment is defined as: enum ValidationStatus { Success, Failed // Later can be added Warning, Info etc. } Now the problem is how to pass the ValidationResult object to the UI. I see 3 options: 1. throw an exeception which has a property of type ValidationResult. The UI then can catch the exception and proceed. Looks a bit messy to me... Pros: Force the UI to handel the validation. Cons: Looks like a bad design. UI code would be messy... 2. Fire an event on a "global" object accessible from both UI and components. "Recomment" the UI to attach an event handler... Pros: UI code should be better organized... Cons: UI is not forced to handle the event... 3. Use some kind of queue to add the ValidationResult objects from the components and poll them from the UI. Pros: ? Cons: ? Any thoughts are welcome. Thanx, Albert [quoted text, click to view] "Alan Fisher" <Gobba@newsgroup.nospam> wrote in message news:ezii4awkFHA.2852@TK2MSFTNGP14.phx.gbl... >I am building a stateless distributed web application which has validation >of information performed in many layers. Most of the validation will be >repeated in both the UI and business layers as the code is structured to >also expose functionality as a web service. More advanced validation will >be done in both the business layer and data layer e.g. validating groups of >related properties or related information in rows of data > > When validating the information for 'anticipated' problems (errors and > warnings), I want to collect all of the various errors/warnings and report > them back to the UI as some sort of collection. Ideally, I would prefer > not to pass the collection between methods so was looking at possibly > using a singleton but I would have to somehow isolate the collection per > user's session since the app is 'mostly' stateless. > > I have searched the net and found many great articles on Exception > Management but nothing detailed on validation. Can anyone recommend an > approach or point me to some articles? > > TIA > Alan > > > > >
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