In my project we are using MongoTemplate, which is injected by spring
private final MongoTemplate mongoTemplate;
I know mongo template implements MongoOperations, ApplicationContextAware, so we get context aware method with template, which we do not get if I use the mongo operation type object like below (spring will inject mongo template object in it)
private final MongoOperations mongoOperations;
My doubt is
1. Are we not violating "programming to interface" paradigm doing that
2. Which pattern should we use and why?
Related
I see that EF Core 2 has EF.Functions property EF Core 2.0 Announcement which can be used by EF Core or providers to define methods that map to database functions or operators so that those can be invoked in LINQ queries. It included LIKE method that gets sent to the database.
But I need a different method, SOUNDEX() that is not included. How do I write such a method that passes the function to the database the way DbFunction attribute did in EF6? Or I need to wait for MS to implement it? Essentially, I need to generate something like
SELECT * FROM Customer WHERE SOUNDEX(lastname) = SOUNDEX(#param)
Adding new scalar method to EF.Functions is easy - you simply define extension method on DbFunctions class. However providing SQL translation is hard and requires digging into EFC internals.
However EFC 2.0 also introduces a much simpler approach, explained in Database scalar function mapping section of the New features in EF Core 2.0 documentation topic.
According to that, the easiest would be to add a static method to your DbContext derived class and mark it with DbFunction attribute. E.g.
public class MyDbContext : DbContext
{
// ...
[DbFunction("SOUNDEX")]
public static string Soundex(string s) => throw new Exception();
}
and use something like this:
string param = ...;
MyDbContext db = ...;
var query = db.Customers
.Where(e => MyDbContext.Soundex(e.LastName) == MyDbContext.Soundex(param));
You can declare such static methods in a different class, but then you need to manually register them using HasDbFunction fluent API.
EFC 3.0 has changed this process a little, as per https://learn.microsoft.com/en-us/ef/core/what-is-new/ef-core-3.0/breaking-changes#udf-empty-string
Example of adding CHARINDEX in a partial context class:
public partial class MyDbContext
{
[DbFunction("CHARINDEX")]
public static int? CharIndex(string toSearch, string target) => throw new Exception();
partial void OnModelCreatingPartial(
ModelBuilder modelBuilder)
{
modelBuilder
.HasDbFunction(typeof(MyDbContext).GetMethod(nameof(CharIndex)))
.HasTranslation(
args =>
SqlFunctionExpression.Create("CHARINDEX", args, typeof(int?), null));
}
}
I'm using Objectify and wish to have its Key<> type passed around in my API. I've created an ApiTransformer, but my questions is where to declare it, since the serialized Key<> class is not available, hence I cannot declare its transformer as a class annotation. I tried declaring it in the #Api annotation, but it doesn't work, I still get the error:
There was a problem generating the API metadata for your Cloud Endpoints classes: java.lang.IllegalArgumentException: Parameterized type com.googlecode.objectify.Key<[my package].User> not supported.
The ApiTransformer looks like:
public class KeyTransformer implements Transformer<Key<?>, String> {
public String transformTo(Key<?> in) {
return in.getString();
}
public Key<?> transformFrom(String in) {
return Key.valueOf(in);
}
}
And in my #Api I have:
#Api(name = "users", version = "v1",transformers = {KeyTransformer.class})
Unfortunately you can't. As you said you need to declare it on the Key class, your only chances to make this work are either.
1) Recompile the Key class for objectify with the #transformer annotation.
2) Extend the Key class with your own implementation and define the transformer there.
I don't really like any of those options so the way i usually resolve this is to hide the key object getter (by using #ApiResourceProperty(ignored=AnnotationBoolean.TRUE)) and only expose the id from that key.
That way you get a Endpoints frendly object, the only downside is you'll have to reconstitute the key using Key.create(YourClass.class, longId) manually whenever you need it.
You can add transforms to 3rd party classes by listing the transform in #Api annotation. I'm not dead sure it'll work parameterized class, but I don't see why not.
https://cloud.google.com/appengine/docs/java/endpoints/javadoc/com/google/api/server/spi/config/Api#transformers()
I'm using XmlSerializer. I've had no problems with it until now. I updated Silverlight from 4 to 5 and at the same time also updated the WCF RIA Services from v1 SP1 to v1 SP2. Now the following line gives me an error.
XmlSerializer s = new XmlSerializer(typeof(MyCustomObject));
The error is:
System.InvalidOperationException: System.ServiceModel.DomainServices.Client.EntityConflict cannot be serialized because it does not have a parameterless constructor.
The object I'm using (MyCustomObject in the sample) has not changed in any way so I'm starting to think it's either SL5 or the new RIA Services that is breaking my code. I didn't find any breaking changes document or mentions that this could happen. I don't know why it has a problem with EntityConflict since I'm not using any entities within my object.
Has anyone seen an error like this and/or know how to solve it?
UPDATE!
The final property that the error message says before EntityConflict is an Entity. I think that makes a difference but it has been working before. I'd also like to know why the serializer already tries to serialize the object in the constructor?
public static XmlSerializer GetEntityXmlSerializer<TEntity>()
where TEntity : Entity
{
XmlAttributes ignoreAttribute = new XmlAttributes()
{
XmlIgnore = true,
};
// use base class of Entity,
// if you use type of implementation
// you will get the error.
Type entityType = typeof(Entity);
var xmlAttributeOverrides = new XmlAttributeOverrides();
xmlAttributeOverrides.Add(entityType, "EntityConflict", ignoreAttribute);
xmlAttributeOverrides.Add(entityType, "EntityState", ignoreAttribute);
return new XmlSerializer(typeof(TEntity), xmlAttributeOverrides);
}
I am not sure why this would be happening, RIA Services entities are not XmlSerializable objects and the entities themselves are not decorated with the [Serializable] attribute. Have you added partial classes on the client side which decorate the entities with [Serializable] or modified the code generation in some way?
I got around this problem by using intermediary serializable POCO objects which were copies of my custom objects (which were inherited from Entity). The POCO objects did not inherit from Entity. I just updated their values from the original Entity objects. They then serialized quite nicely. Of course, when you de-serialize you need to update your Entity objects from the POCO objects.
I am looking for a maven plugin that will auto generate EntityProxy interfaces from my domain classes.
The class could implement the various interfaces to be generated and then each field or accessor method could use an annotation.
public class MyDomainObject implements MyDOProxyFoo, MyDOProxyBar {
#ExposedBy({MyDOProxyFoo.class})
public String foo;
#ExposedBy({MyDOProxyBar.class})
public String bar;
#ExposedBy({MyDOProxyFoo.class,MyDOProxyBar.class})
public String foobar;
...
}
Then the getters/setters for the respective fields would be in the respective generated interfaces.
You could do something like a readonly attribute in the annotation to only expose a getter in the specified interfaces.
...
#ExposedBy({MyDOProxyBar.class}, readOnly = {MyDOProxyFoo.class})
public String bar;
...
I could run something like
mvn rfproxygen:generateproxies
and I would have all my proxy interfaces nicely created in the generated sources directory.
I guess the argument is deciding wether you should have service data binding logic in your domain model.
I don't know a maven plugin that is capable of generating proxies but there is an issue addressing this for GWTP. Maybe this will of interests for you if it's finished.
I've got an application set up with RIA Services, Entity Framework 4, and Silverlight 4. It is set up in the standard fashion prescribed on MSDN here: Walkthrough: Creating a RIA Services Solution
I've written a new method (or property) against one of the entity objects which resides on the server; I would like this method (or property) to also be generated (automagically) on the client. i.e.
I have a table in my database called Customer which has two fields: FirstName and LastName
(ASP.NET project - server side) EF has created a corresponding partial class called Protocol that has two properties: FirstName and LastName
(ASP.NET project - server side) In another file, I'm using the partial class mechanism to define a method (or property) to return the FirstName and LastName together in a string, e.g.
public function ReturnFullName() as String ...
public property FullName() as String ...
Is there a way for ReturnFullName() and FullName() to be generated in on the client side (my Silverlight application)? Or do I have to implement the method / property on the client side as well?
Create a .shared.cs or .shared.vb file with a partial class of the entity in it.
For example:
Partial Public Class Persoon
Public Function GetFullName() As String
Return Me.Voornaam & " " & Me.Naam
End Function
End Class
public partial class Persoon
{
public string GetFullName()
{
return this.Voornaam + " " + this.Naam;
}
}
It will then generate on client side to.
Methods in your Domain objects on the server side are not generated on the client side. (One reason for that is that obviously you could use .NET Framework features in these methods that are not available in Silverlight.) Properties are just copied with their signature, using class variables.
A solution to that problem is having a partial .cs file for your Customer class where you define these methods and create a link to that file in your Silverlight project. Of course, you can only use libraries in the using statements that are also available in Silverlight.