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Java stored procedures in Oracle, a good idea?

- by Scott A

I'm considering using a Java stored procedure as a very small shim to allow UDP communication from a PL/SQL package. Oracle does not provide a UTL_UDP to match its UTL_TCP. There is a 3rd party XUTL_UDP that uses Java, but it's closed source (meaning I can't see how it's implemented, not that I don't want to use closed source). An important distinction between PL/SQL and Java stored procedures with regards to networking: PL/SQL sockets are closed when dbms_session.reset_package is called, but Java sockets are not. So if you want to keep a socket open to avoid the tear-down/reconnect costs, you can't do it in sessions that are using reset_package (like mod_plsql or mod_owa HTTP requests). I haven't used Java stored procedures in a production capacity in Oracle before. This is a very large, heavily-used database, and this particular shim would be heavily used as well (it serves as a UDP bridge between a PL/SQL RFC 5424 syslog client and the local rsyslog daemon). Am I opening myself up for woe and horror, or are Java stored procedures stable and robust enough for usage in 10g? I'm wondering about issues with the embedded JVM, the jit, garbage collection, or other things that might impact a heavily used database.

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Interfaces with structs, by reference using Generics

- by Fraga

I can't pass by reference an interface with a struct in it, what am I doing wrong? Here is the example code: class Processor<T> where T : new() { public Processor() { Data = new T(); } public T Data; } class PeriodsProcessor : Processor<Periods> { public PeriodsProcessor() { DataBase DB = new DataBase(); Console.WriteLine(Data.Value); DB.ModifyData<Period>(Data); Console.WriteLine(Data.Value); Console.ReadLine(); } } public class Period { public string Name; } public interface IDataTable<T> { string Value { get; set; } T Filter { get; set; } } [Serializable] public struct Periods : IDataTable<Period> { public string Value { get; set; } public Period Filter { get; set; } } public class DataBase { public void ModifyData<T>(IDataTable<T> data) where T : new() { data.Value = "CHANGE"; } } class Program { static void Main(string[] args) { PeriodsProcessor PeriodsProcessor = new PeriodsProcessor(); } }

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Using generics in Unity ... InvalidCastException

- by Sunny D

Hi, My interface definition is: public interface IInterface where T:UserControl My class definition is: public partial class App1Control : UserControl, IInterface The unity section of my app.config looks as below: <unity> <typeAliases> <typeAlias alias="singleton" type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager, Microsoft.Practices.Unity" /> <typeAlias alias="myInterface" type="MyApplication.IInterface`1, MyApplication" /> <typeAlias alias="App1" type="MyApplication.App1Control, MyApplication" /> </typeAliases> <containers> <container> <types> <type type="myInterface" mapTo="App1" name="Application 1"> <lifetime type="singleton"/> </type> </types> </container> </containers> </unity> The app runs fine but, the following code gives a InvalidCastException container.Resolve<IInterface<UserControl>>("Application 1"); The error message is : Unable to cast object of type 'MyApplication.App1Control' to type 'MyApplication.IInterface`1[System.Windows.Forms.UserControl]' I believe there is a minor mistake in my code ... but am not able to figure out what. Any thoughts?

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Starting to Program C++ and Java

- by user0321

So as the title states, I'm trying to start programming in C++ and Java. I took C++ and Java courses in high school and I'm trying to get back into it. Of course all I want to get working now is a simple "Hello World" program. Couple of things: I want to use an IDE. I've decided on Eclipse. I'm just confused about how I go about downloading/using it. For Java: I get stuck right on their download page. They show Eclipse Classic, Eclipse IDE for Java developers and Eclipse IDE for Java EE Developers. I only programmed in Notepad and compiled in command prompt. Question 1: Which version of Eclipse should I download? Question 2: Do I need to install the Java JDK or does it come built into Eclipse? For C++: I guess I download the separate Eclipse IDE for C/C++ developers? I'm not too sure. I remember using Microsoft Visual for C++. I remember it being weird though. Anyways Question 3: Which version of Eclipse should I download? Question 4: Does C++ have a Development Kit or does it come built into Eclipse?

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WPF View/ViewModels using Generics- how?

- by Investor5555

New to WPF, so please bear with me... Suppose I have 2 tables in SQL Thing OtherThing Both have the exact same fields: ID (int) Name (string) Description (string) IsActive (bit/bool) DateModified (DateTime) So, I want to create one Model (not two) and do something like this: BaseModel<T>() { public int ID {get;set;} ... } etc. (of course, using the INotifyPropertyChanged, just trying to keep the code simple). I want to be able to create a BaseView and BaseViewModel that would work with whatever model conforms to the Thing/OtherThing. I am really at a loss as to what to do here to make this generic, so I don't have to have a ThingView/ThingViewModel and a OtherThingView/OtherThingViewModel... It seems that this should be simple, but I cannot seem to figure it out. Does anyone have a code example where they could interchange various items from a dropdown list using one view, one ViewModel, and one base datamodel (and switching out the type from a dropdown)? For example, a combobox has 3 identical table structures for Thing OtherThing SomeThing and on selection changed, I want to pull the data from whatever table was selected, to be able to do standard CRUD operations on any of these 3 tables, without having to create concrete classes for each view/viewmodel.

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Refactoring exercise with generics

- by Berryl

I have a variation on a Quantity (Fowler) class that is designed to facilitate conversion between units. The type is declared as: public class QuantityConvertibleUnits<TFactory> where TFactory : ConvertableUnitFactory, new() { ... } In order to do math operations between dissimilar units, I convert the right hand side of the operation to the equivalent Quantity of whatever unit the left hand side is in, and do the math on the amount (which is a double) before creating a new Quantity. Inside the generic Quantity class, I have the following: protected static TQuantity _Add<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount + equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } protected static TQuantity _Subtract<TQuantity>(TQuantity lhs, TQuantity rhs) where TQuantity : QuantityConvertibleUnits<TFactory>, new() { var toUnit = lhs.ConvertableUnit; var equivalentRhs = _Convert<TQuantity>(rhs.Quantity, toUnit); var newAmount = lhs.Quantity.Amount - equivalentRhs.Quantity.Amount; return _Convert<TQuantity>(new Quantity(newAmount, toUnit.Unit), toUnit); } ... same for multiply and also divide I need to get the typing right for a concrete Quantity, so an example of an add op looks like: public static ImperialLengthQuantity operator +(ImperialLengthQuantity lhs, ImperialLengthQuantity rhs) { return _Add(lhs, rhs); } The question is those verbose methods in the Quantity class. The only change between the code is the math operator (+, -, *, etc.) so it seems that there should be a way to refactor them into a common method, but I am just not seeing it. How can I refactor that code? Cheers, Berryl

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c# Generics problem

- by UpTheCreek

Can anyone tell me why this does not work? I would have thought the constraint would make it valid. public class ClassA<T> where T : ICommon { public ClassA() { ClassB b = new b(); IEnumerable<T> alist = new IList<T>; b.items = alist; //Error: cannot convert from IEnumerable<T> to IEnumerable<ICommon>' } } public class ClassB { IEnumerable<ICommon> items { get; set;} .... }

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C# simpler run time generics

- by Hellfrost

Is there a way to invoke a generic function with a type known only at run time? I'm trying to do something like: static void bar() { object b = 6; string c = foo<typeof(b)>(); } static string foo<T>() { return typeof (T).Name; } Basically I want to decide on the type parameter only at run time, but the function I'm calling depends on the type parameter. Also I know this can be done with reflections... but it's not the nicest solution to the problem... I'm sort of looking for dynamic features in C#...

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With this generics code why am I getting "Argument 1: cannot convert from 'ToplogyLibrary.Relationsh

- by Greg

Hi, Any see why I'm getting a "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase' to 'TRelationship'" in the code below, in CreateRelationship() ? public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, TNode> Nodes { get; private set; } public List<TRelationship> Relationships { get; private set; } // Constructors protected TopologyBase() { Nodes = new Dictionary<TKey, TNode>(); Relationships = new List<TRelationship>(); } // Methods public TNode CreateNode(TKey key) { var node = new TNode {Key = key}; Nodes.Add(node.Key, node); return node; } public void CreateRelationship(TNode parent, TNode child) { // Validation if (!Nodes.ContainsKey(parent.Key) || !Nodes.ContainsKey(child.Key)) { throw new ApplicationException("Can not create relationship as either parent or child was not in the graph: Parent:" + parent.Key + ", Child:" + child.Key); } // Add Relationship var r = new RelationshipBase<TNode>(); r.Parent = parent; r.Child = child; Relationships.Add(r); // *** HERE *** "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase<TNode>' to 'TRelationship'" } } public class RelationshipBase<TNode> { public TNode Parent { get; set; } public TNode Child { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } }

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C# Fun with Generics - Mutual Dependencies

- by Kenneth Cochran

As an experiment I'm trying to write a generic MVP framework. I started with: public interface IPresenter<TView> where TView: IView<IPresenter<... { TView View { get; set;} } public interface IView<TPresenter> where TPresenter:IPresenter<IView<... { TPresenter Presenter { get; set; } } Obviously this can't work because the types of TView and TPresenter can't be resolved. You'd be writing Type<Type<... forever. So my next attempt looked like this: public interface IView<T> where T:IPresenter { ... } public interface IView:IView<IPresenter> { } public interface IPresenter<TView> where TView: IView { ... } public interface IPresenter: IPresenter<IView> { ... } This actually compiles and you can even inherit from these interfaces like so: public class MyView : IView, IView<MyPresenter> { ... } public class MyPresenter : IPresenter, IPresenter<MyView> { ... } The problem is in the class definition you have to define any members declared in the generic type twice. Not ideal but it still compiles. The problem's start creeping up when you actually try to access the members of a Presenter from a View or vice versa. You get an Ambiguous reference when you try to compile. Is there any way to avoid this double implementation of a member when you inherit from both interfaces? Is it even possible to resolve two mutually dependent generic types at compile time?

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Using generics in F# to create an EnumArray type

- by Matthew

I've created an F# class to represent an array that allocates one element for each value of a specific enum. I'm using an explicit constructor that creates a dictionary from enum values to array indices, and an Item property so that you can write expressions like: let my_array = new EnumArray<EnumType, int> my_array.[EnumType.enum_value] <- 5 However, I'm getting the following obscure compilation error at the line marked with '// FS0670' below. error FS0670: This code is not sufficiently generic. The type variable ^e when ^e : enum<int> and ^e : equality and ^e : (static member op_Explicit : ^e -> int) could not be generalized because it would escape its scope. I'm at a loss - can anyone explain this error? type EnumArray< 'e, 'v when 'e : enum<int> and 'e : equality and ^e : (static member op_Explicit : ^e -> int) > = val enum_to_int : Dictionary<'e, int> val a : 'v array new() as this = { enum_to_int = new Dictionary<'e, int>() a = Array.zeroCreate (Enum.GetValues(typeof<'e>).Length) } then for (e : obj) in Enum.GetValues(typeof<'e>) do this.enum_to_int.Add(e :?> 'e, int(e :?> 'e)) member this.Item with get (idx : 'e) : 'v = this.a.[this.enum_to_int.[idx]] // FS0670 and set (idx : 'e) (c : 'v) = this.a.[this.enum_to_int.[idx]] <- c

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Service locator for generics

- by vittore

Hi everyone, I have say a dozen types T which inherit from EntityObject and IDataObject. I have generic the following interface IDataManager<T> where T : EntityObject, IDataObject ... I have also base class for data managers BaseDataManager<T> : IDataManager<T> where T : EntityObject, IDataObject .... And i have particular classes public class Result : EntityObject, IDataObject .... public class ResultDataManager : BaseDataManager<Result> ... I want to implement service locator, which will return instance of IDataManager<T> for T But I stucked how to implement it in a neat way without a lot of castings. Any ideas?

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C# generics method invocation

- by Firat KÜÇÜK

Hi, i have some polymorphic methods and i want to call via using an intermediate method. Following class is the simplified version of my program. class Program { public class A { } public class B { } public class C { } public void SomeMethod(A value) { Console.WriteLine("A value"); } public void SomeMethod(B value) { Console.WriteLine("B value"); } public void SomeMethod(C value) { Console.WriteLine("C value"); } static void Main(string[] args) { Program p = new Program(); // code block p.IntermediateMethod<A>(new A()); p.IntermediateMethod<B>(new B()); p.IntermediateMethod<C>(new C()); } public void IntermediateMethod<T>(T value) { // code block SomeMethod(value); // code block } }

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Java EE Website Planning Questions

- by Tom Tresansky

I'm a .NET programming who is soon moving to the Java EE world. I have plenty of experience with .NET web technologies, web services, WebForms and MVC. I am also very familiar with the Java language, and have written a few servlets and modified a couple of JSP pages, but I haven't touched EE yet. I'd like to set up a public website using Java EE so I can familiarize myself with whats current. I'm thinking just a technology playground at this point with no particular purpose in mind. What Java technologies are the current hotness for this sort of thing? (For example, if someone asked me what I'd recommend learning to set up a new .NET site, I'd say use ASP MVC instead of WebForms and recommend LINQ-to-SQL as a quick, simple and widely used ORM.) So, what I'd like to know is: Is there a recommended technology for the presentation layer? Is JSP considered a good approach, or is there anything cleaner/newer/more widespread? Is Hibernate still widely used for persistence? Is it obsolete? Is there anything better out there? (I've worked with NHibernate some, so I wouldn't be starting from scratch.) Is cheap Java EE web hosting available? What should I know being a .NET web developer moving to the Java world?

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Do you think Scala will be the dominant JVM langauge, ie be the next Java? [on hold]

- by user1037729

From what I've read about Scala do far I think it has some nice features but I do not think it should be "the next Java". It might however end up being the next Java (due to fashion rather than fact) but lets not hope it does not... To me adds a lot of complexity over Java which is a simple and scalable language. Scala Pattern matching allows you to perform some type/value checking in a more concise way, this is possible in Java, Scala's pattern matching has a limit to it, you cannot continuously match deeper and deeper down the object graph, so why not just stick to Java and use decent invariants? Scala provides tuples, easy enough to make in Java, create a static factory method and it all reads nicely too. Scala provides mixins, why not just use composition? I believe Scala implicit's are bad, they can lead to code becoming complex and hard to maintain, explicitness is good. Scala provides closures, well they will be in Java 8 too. Scala has lazy keyword for lazy instantiation, this is easy enough to do in Java by calling a getter which creates the instance when needed, no hidden magic here. Scala can be used with AKKA, well so can Java, there is an Java AKKA implementation. Scala offers addition functional features but these can all be created in Java, there are many frameworks with have implemented functional features in Java. All in all Scala seems to offer is addition complexity and thats it...

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C# Pass Generics At Runtime

- by TheCloudlessSky

I have a method like the following: public IEnumerable<T> GetControls<T>() : where T : ControlBase { // removed. } I then created a class: public class HandleBase<TOwner> : ControlBase : TOwner { // Removed } I'd like to be able to call GetControls<HandleBase<this.GetType()>>; where it would use the type of THIS class to pass to the HandleBase. This would in essentially get all HandleBase that have an owner of THIS type. How can I achieve this?

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Circular dependency with generics

- by devoured elysium

I have defined the following interface: public interface IStateSpace<State, Action> where State : IState where Action : IAction<State, Action> // <-- this is the line that bothers me { void SetValueAt(State state, Action action); Action GetValueAt(State state); } Basically, an IStateSpace interface should be something like a chess board, and in each position of the chess board you have a set of possible movements to do. Those movements here are called IActions. I have defined this interface this way so I can accommodate for different implementations: I can then define concrete classes that implement 2D matrix, 3D matrix, graphs, etc. public interface IAction<State, Action> { IStateSpace<State, Action> StateSpace { get; } } An IAction, would be to move up(this is, if in (2, 2) move to (2, 1)), move down, etc. Now, I'll want that each action has access to a StateSpace so it can do some checking logic. Is this implementation correct? Or is this a bad case of a circular dependence? If yes, how to accomplish "the same" in a different way? Thanks

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Performance of C# method polymorphism with generics

- by zildjohn01

I noticed in C#, unlike C++, you can combine virtual and generic methods. For example: using System.Diagnostics; class Base { public virtual void Concrete() {Debug.WriteLine("base concrete");} public virtual void Generic<T>() {Debug.WriteLine("base generic");} } class Derived : Base { public override void Concrete() {Debug.WriteLine("derived concrete");} public override void Generic<T>() {Debug.WriteLine("derived generic");} } class App { static void Main() { Base x = new Derived(); x.Concrete(); x.Generic<PerformanceCounter>(); } } Given that any number of versions of Generic<T> could be instantiated, it doesn't look like the standard vtbl approach could be used to resolve method calls, and in fact it's not. Here's the generated code: x.Concrete(); mov ecx,dword ptr [ebp-8] mov eax,dword ptr [ecx] call dword ptr [eax+38h] x.Generic<PerformanceCounter>(); push 989A38h mov ecx,dword ptr [ebp-8] mov edx,989914h call 76A874F1 mov dword ptr [ebp-4],eax mov ecx,dword ptr [ebp-8] call dword ptr [ebp-4] The extra code appears to be looking up a dynamic vtbl according to the generic parameters, and then calling into it. Has anyone written about the specifics of this implementation? How well does it perform compared to the non-generic case?

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C# Generics Question

- by TheCloudlessSky

Would it be possible to do something like the following in c#? Basically TParent and TChildren should be types of the class A but not necessairly have the same types that were passed in. I know this may sound confusing but I want to strongly type the children and parents of a particular object, but at the same time they must be of the same type. Because TParent inherits from A this would imply that it requires type parameters that inherit from A but using potentially different types. public class A<TParent, TChildren> where TParent : A where TControls : A { TParent Parent; List<TChildren> Children; } or more easily seen here: public class A<TParent, TChildren> where TParent : A<?, ?> where TChildren : A<?, ?> { TParent Parent; List<TChildren> Children; } I hope this isn't too confusing. Is this at all possible? Thanks :)

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A c# Generics question involving Controllers and Repositories

- by UpTheCreek

I have a base repository class which contains all the common repository methods (as generic): public abstract class BaseRepository<T, IdType> : IBaseRepository<T, IdType> My repositories from this base e.g.: public class UserRepository : BaseRepository<User, int>, IUserRepository I also have a base controller class containing common actions, and inherit from this in controllers. The repository is injected into this by DI. E.g. public class UserController : BaseController<User> { private readonly IUserRepository userRepository; public UserController (IUserRepository userRepository) { this.userRepository= userRepository; } My question is this: The base controller needs to be able to access the repository methods that are defined in the base repository. However I'm passing in via DI a different repository type for each controller (even though they all inherrit from the base repository). How can the base controller somehow access the repository that is passed in (regardless of what type it is), so that it can access the common base methods?

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Casting between value types on a class using generics

- by marcelomeikaru

In this section of a function (.NET 2.0): public void AttachInput(T input, int inIndex) where T : struct { if (input is int) { Inputs.Add(inIndex, (int)input); InputCount++; IsResolved = false; } } The compiler shows the error "Cannot convert type 'T' to 'int'. So, I used Convert.ToInt32() which worked - but does it box input to an object? Is there a better solution? Thanks

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Extension method return using generics

- by Steven de Salas

Is it possible to return a generic type using extension methods? For example, I have the following method: // Convenience method to obtain a field within a row (as a double type) public static double GetDouble(this DataRow row, string field) { if (row != null && row.Table.Columns.Contains(field)) { object value = row[field]; if (value != null && value != DBNull.Value) return Convert.ToDouble(value); } return 0; } This is currently used as follows: double value = row.GetDouble("tangible-equity"); but I would like to use the following code: double value = row.Get<double>("tangible-equity"); Is this possible and if so, what would the method look like?

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C# Generics Casting

- by Nippysaurus

Visual sutdio 2008 has the ability to automatically create unit test stubs. I have used this to create some basic unit tests, but I am confused by something: private class bla : BaseStoreItem { // } /// <summary> ///A test for StoreData ///</summary> public void StoreDataTestHelper<T>() where T : BaseStoreItem { FileStore<T> target = new FileStore<T>(); // TODO: Initialize to an appropriate value BaseStoreItem data = new bla(); target.StoreData(data); } [TestMethod()] public void StoreDataTest() { //Assert.Inconclusive("No appropriate type parameter is found to satisfies the type constraint(s) of T. " + // "Please call StoreDataTestHelper<T>() with appropriate type parameters."); StoreDataTestHelper<bla>(); } Why do I get "Error: Cannot convert type 'StorageUnitTests.FileStoreTest.bla' to 'T'" when T is type "bla"? I know "bla" is not a good function name, but its just an example.

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Generics and Derived Classes .NET 3.5

- by Achilles

Consider the following where class "Circle" inherits from "Shape": dim objListOfCircles as new List(of Circle) DrawShapes(objListOfCirlces) Private sub DrawShapes(byref objListOfShapes as List(of Shape)) for each objShape as Shape in objListOfShapes objShape.Draw() next end sub I can't get this to work. What is the explaination as to why this doesn't work?

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Creating dynamic generics at runtime using Reflection

- by MPhlegmatic

I'm trying to convert a Dictionary< dynamic, dynamic to a statically-typed one by examining the types of the keys and values and creating a new Dictionary of the appropriate types using Reflection. If I know the key and value types, I can do the following: Type dictType = typeof(Dictionary<,>); newDict = Activator.CreateInstance(dictType.MakeGenericType(new Type[] { keyType, valueType })); However, I may need to create, for example, a Dictionary< MyKeyType, dynamic if the values are not all of the same type, and I can't figure out how to specify the dynamic type, since typeof(dynamic) isn't viable. How would I go about doing this, and/or is there a simpler way to accomplish what I'm trying to do?

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