I try to use Between predicate to compare the current datetime with a range of date time.
I reference mscorlib assembly and use get_Now() within DateTime class in the assembly to get DateTimeNow. I have problem to compare this current datetime with the range.
my condition is like:
DateTimeNow is between 2012-08-03 07:00:00 and 2012-08-04 07:00:00
DateTimeNow at my region should be 2012-08-03 16:33:20 for this moment. It should between the range I specified. But it seems does not work. If I replace DateTimeNow with 2012-08-03 16:33:20, it works.
It seems for some reason my DateTimeNow does not work. Anyone has any idea?
I found to use Get_Date() function in .net mscorlib assembly, you have to modify your machine registry
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\BusinessRules\3.0\StaticSupport (DWORD), give value 1
Details in:
http://blogs.msdn.com/b/richardbpi/archive/2005/11/14/492489.aspx
http://kinnaribhute.blogspot.co.nz/2008/04/some-interesting-stuff-about-biztalk.html
I am not sure how this will affect the production server, if the production server environment is not clustered with multiple node, there will be an outage for reboot the server.
There is an impedance mismatch between the way facts are logically modelled in the engine and the way objects are modelled in .NET code, and one effect of this is the problem of calling static methods. If you set the StaticSupport flag as described by Xiao Han, the engine changes its behaviour, treating static methods much as if they were built-in functions or predicates. By default, however, the engine treats static methods as behaviour of facts. Physically, a fact is an object in the working memory of the engine, and each fact has to be asserted to the engine before it's methods can be used. So, to call the static Now property getter on DateTime, you first have to assert a DateTime object to the engine. Of course, DateTime is a value type (structure), but that's OK because, when you execute a rule set, you assert a single fact as an Object or a collection of facts as an Object array. .NET will automatically box a DateTime (internally wrap it as an object) passed in this way.
It seems mad, I realise, having to assert an object to the engine in order to call a static method (or, in this case, a property getter, which is really a method, of course) on the type of that object. It would probably have been better if the engine had been built to treat static methods as built-ins by default. However, that was not the case. In addition, it would have been much better if Microsoft had implemented the StaticSupport flag at the level of individual rule sets, or even individual rules. Implementing it in the registry (machine-level), or alternatively configuring it in the .config file (application-level; use ) in this way can pose real problems because it can break rule sets that were written to use the opposite value of the flag.
Another point to bear in mind in that the Static Support can also be set to '2'. In this case, if you call a static method with no parameters, or if you call it with constant values only, and if you call it as a predicate in a condition or as an argument to another function, then the engine will evaluate the static member just once and cache the result.
Related
I have an oData model with a couple of one-to-many relationship, say person->addresses and person->driving-licences. I would like to be able to sort the result set based on properties in the address entity and driving licence entity. As there could be more than one address, I would initially select a single item from the addresses set, based on a property called IsPrimary. As there could be more that one driving licence, I would select the 'UK' driving licence. Is this possible?
I was hoping I could do something like:
/people?$expand=addresses($filter=isPrimary eq true),drivinglicences($filter=country eq 'UK')&$orderby=addresses/postcode,drivinglicences/active
Unfortunately I get the following error:
"The query specified in the URI is not valid. The parent value for a property access of a property 'isPrimary' is not a single value. Property access can only be applied to a single value."
Does anyone know if what I'm trying to do is supported by the spec? Or whether it is an issue with my query? Or whether it is an issue with the .NET library.
I'm using:
Microsoft.AspNet.OData - 7.2.3
Many Thanks.
What you see here is by design, or rather not supported by the specification, the error message even highlights the only type of expressions supported:
The query specified in the URI is not valid. The parent value for a property access of a property 'isPrimary' is not a single value. Property access can only be applied to a single value.
So the simplest solution is to modify the API either to include a Function bound to the people collection that applies the $filter or $order directly, or a Function that returns the data in a new shape, one that only has perhaps a singleton PrimaryAddress property. How you include driving license in this result is up to you, it could even be a parameter to the function, perhaps your people controller has a queryable function with this signature:
[EnableQuery]
public IHttpActionResult WithLicences(string countryCode)
However that is out of the scope of OPs question about specific syntax support
Although it seems like an important feature, we must remember that $select (Projection) and $filter are evaluated at different points in time, OData queries follow a similar execution sequence to SQL however the filter criteria and $orderby are evaluated separately, and the projection of the resultset is the last evaluation to be applied.
Due to $filter and $orderby being applied independently, neither concept is even aware of the other and as such neither can reference or assume to be applied before the other.
You can prove this by specifying a field in the $orderby and/or $filter that is not included in the $select, you can even reference singleton navigation fields that are not included in an $expand and the query will evaluate correctly.
The OData spec is similar to a law document, in that to properly understand and apply it we need to understand the original intent of the authors. We can get an initial understanding from the early listing of Addressing Entities
Addressing Entities describes functions that can be bound to collections or entities that return either a single entity or a collection of entities
By allowing special provision of custom functions to be applied the authors are encouraging API designers to provide natural extensions to their resource endpoints that can facilitate the execution of pre-determined queries that may be otherwise complex or problematic to express in pure OData query syntax.
In other words, we are encouraged to customise our APIs to make them easier for the end process to consume, and to guide the consuming developer to make the best use of the API, they shouldn't have to discover everything from first principals.
To achieve OPs type of query in pure SQL would still require either a nested lookup, CTE or self join... advanced syntax. In OData v4, the specification does not provide a syntax for targeting specific items within a collection for path expressions (of which $orderby derives from)
5.1.1.15 Path Expressions
Properties and navigation properties of the entity type of the set of resources that are addressed by the request URL can be used as operands or function parameters, as shown in the preceding examples.
Properties of complex properties can be used via the same syntax as in resource paths, i.e. by specifying the name of a complex property, followed by a forward slash (/) and the name of a property of the complex property, and so on,
Properties and navigation properties of entities related with a target cardinality 0..1 or 1 can be used by specifying the navigation property, followed by a forward slash (/) and the name of a property of the related entity, and so on.
If a complex property is null, or no entity is related (in case of target cardinality 0..1), its value, and the values of its components, are treated as null.
RE: I couldn't find anything explicit in the spec. :)
That is the very thing about the OData specification,the specification does not list what is not supported, only what should be supported. So by omission, if you cannot find a reference to how to do something, then that something is not required to be supported.
Introduction http://docs.oasis-open.org/odata/odata/v4.01/odata-v4.01-part2-url-conventions.html#sec_Introduction ... This specification defines a set of recommended (but not required) rules for constructing URLs to identify the data and metadata exposed by an OData service as well as a set of reserved URL query string operators, which if accepted by an OData service, MUST be implemented as required by this document.
This has been on ongoing discussion held in may threads, recently https://stackoverflow.com/a/55324393/1690217
Many people complain that this is surely a fundamental feature of a data access platform, however it is important to respect the original intent of the OData platform and keep our APIs simple by providing customised endpoints to suit our business domain.
#WebInitParam is an annotation that goes at class level.
It defines initialization parameters for the servlet.
I would like to know, what is the difference between doing this and using static variables, and why do it the #WebInitParam way rather than using statics?
What does defining k/v pairs as #WebInitParams allow you to do that you couldn't do if you declared static variables instead?
I have looked and all I can find is a million people saying how to define #WebInitParams. Well yes that's the easy bit. It's what I can do with that that is really what is of interest.
Thanks very much.
From a "raison d'etre" perspective, the annotation exists as a better design and architecture alternative to just peppering a class with static fields. #WebInitParam is a self-documenting approach to the initialization parameters a servlet or filter class needs, available via web.xml as well. It serves this purpose for the end developers as well as the JavaEE platform as a whole.
Think about it this way: in a vanilla project, you have the option of hardcoding a bunch of parameters in the class as static fields, or defining the same parameters in a property file. Which would you pick? Under what circumstances?
From a purely functional angle, apart from the function of using the annotation to override defaults set in web.xml, one other major reason is that you will sometimes need to get a hold of those initialization parameters from another component in your application. Using the annotation essentially increases the visibility of the parameter. In JSF for example, the API allows you to retrieve FacesServlet initialization parameters with:
//get all the parameters
FacesContext.getCurrentInstance().getExternalContext().getInitParameterMap()
//get a specific parameter
FacesContext.getCurrentInstance().getExternalContext().getInitParameter("aParameter");
In JSF-2.3 , it gets even more convenient with the following CDI-enabled injection:
#InitParameterMap Map<String,String> servletParameterMap;
Bear in mind that because it's CDI, it means this facility is available throughout the JavaEE platform, not just in web applications/JSF.
It's going to be a hassle to retrieve init parameters if the only mechanism available is a static field in the servlet class - you'll need to obtain an instance of the filter or servlet to get the static fields in it.
Separately, one could make the argument that maybe one should favour context-params over servlet-params because then, you get even more flexibility that isn't tied to any given servlet. That's a separate matter entirely :)
Just curiously I am asking which is the better method to use Hashtable.keys() or Hashtable.keySet(). Any one would have been sufficient. Why have they given 2 methods with different return types. Is there any performance drawback/benefit of one over the other ?
keySet is there because
it returns a Set view of the keys contained in this Hashtable. The Set is backed by the Hashtable, so changes to the Hashtable are reflected in the Set, and vice-versa. The Set supports element removal (which removes the corresponding entry from the Hashtable), but not element addition.
And keys just returns an enumeration of the keys in this hashtable, no changes will be reflected after getting enumeration.
Besides the funcitonal difference mentioned by Rahul, Hashtable itself is an old artifact of earlier java version and retrofitted to implement Map interface.
So keySet is a later construct required by the Map interface.
Additionally, if this is new code that you are writing, you should read up the api details for this data structure on http://docs.oracle.com/javase/7/docs/api/java/util/Hashtable.html and see if you should consider the guideline and use HashMap or other later Collections instead.
This is a somewhat philosophical issue. I have a .net (but could be any platform) based helper library that parses query string values. Take for example a variable that returns an Int32: my framework has an option that specifies whether this value is required or optional. If it is required but not provided, the framework throws an exception. If it is optional and not specified, it returns a null.
Now an edge case has come up based on users hacking (in a good way) our urls. If they specify a variable with either an invalidly formatted Int32 ("&ID=abc") or provide the variable but not specify a value ("&id="), should the framework throw an exception or should it return a null?
Part of me feels that invalid variables or formats should return a null. It might be valid to argue that even if the parameter is optional, an invalidly formatted query string or value should still throw an exception.
Thoughts?
Since this is philophical ...
On something like an ID, I would agree with Shawn that it is a 404, especially if you are thinking in terms of state. There is no object, so not found. But, ID may not tie directly to a resource in all cases.
If the item is truly optional, a null is okay. But optional should mean "if present it makes the call more specific" in this case and there should always be a fallback. I don't see this in ID, unless the ID is keyed to an optional part of the page.
In the long run, I think you should look at the business reason for the page and what each variable means.
I believe that if a variable is optionaly, providing the variable but not specifying the value is equivalent to ommitting the variable itself. In this case, returning null seems OK.
However, providing an invalidly formatted value ought to cause an Exception, since the intent was to provide a value. In this case the user ought to be notified through some sort of validation mechanism.
A HttpException of 404 (Not Found). Your web application framework should know how to catch these errors and redirect to the proper page.
This is actually a not found error because the resources that the ID is pointing to does not exist.
I suspect there's no "right" answer to your question. If I were a developer using your library, I would expect/hope that the public API would include in its code comments, a description of how the function behaves when the URL param includes bad (wrong type) data.
You might also be able to craft your public API to get the best of both worlds: .NET seems to have adopted the "Parse" / "TryParse" approach in many places. If I'm the caller and I want the function to throw if given invalid data, I call Parse(). If I don't want it to throw, I call TryParse(). In my opinion, that is a nice pattern to follow with your API as well.
Is there a way to set HttpContext.Current.Request.Browser.Type in ASP.NET. That is a read-only, string property. So you cannot really just assign a string to it. Tried initializing Browser property which is of type HttpBrowserCapabilities, but it has only one constructor and does not take any parameters and browser Type is still null. The reason why I want to be able to set Type for browser is that my unit test is failing as Type property is null.
Edit per null check comments:
I could definitely modify code to check for null, but that will be just for my unit test as when the requests come from browsers, that value is never null. Hence not quite excited about doing that. But it can be my last resort.
You can define your own browser definition files which ASP.net will then use. Check out http://forums.asp.net/p/955969/1176101.aspx.
So if you know what browser it's failing on you could setup a browser file for it. However, I agree that checking for null values makes more sense as it accounts for a lot more possiblities that way.
You might want to think about refactoring your code to use HttpContextBase instead of relying directly on the concrete type.
By doing so you could simply create a stub object that provides the behavior you want. Eventually implementing your own HttpBrowserCapabilitiesBase object.
You would then have full control to use your mock types during unit testing. Indeed that is what they were created for.