How to implement spring separated by group singletons

How to implement spring separated by group singletons

By : user2950994
Date : November 17 2020, 11:58 AM
This might help you It can be implemented using custom scope. Create all objects of this scope while initialization and use it in proper way at runtime wiring of beans.
code :

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how to implement a common behavior for regexp singletons in C#?

how to implement a common behavior for regexp singletons in C#?

By : mashhoodgee
Date : March 29 2020, 07:55 AM
should help you out I want to write a singleton to test regular expressions, every singleton has to have its own expression (a singleton for mail, a singleton for identificacion numbers etc.). , What about:
code :
public class RegExpTester
        private readonly Regex engine;

        protected RegExpTester( string expression )

            if ( string.IsNullOrEmpty( expression ) )
                throw new ArgumentException( "expression null or empty" );
            engine = new Regex( expression );

        public bool test( string strToBeTested )
            return engine.IsMatch( strToBeTested );

    public sealed class emailTester : RegExpTester
        static emailTester instance = new emailTester();

        emailTester() : base( "some mail expression" ) { }

        public static emailTester Instance
                return instance;
emailTester.Instance.test("some text");
Using enums to implement utility classes and singletons

Using enums to implement utility classes and singletons

By : Sergiy Povazhuk
Date : March 29 2020, 07:55 AM
seems to work fine I don't really agree with the first use of an enum from that post. If you want an uninstantiable utility class, just give it a private constructor. It's that simple, and the enum provides no added benefit in that situation that I see.
The use of enums for singletons in utility classes is great, but I would generally try to keep the fact that an enum is being used an internal implementation detail. See, for example, Guava's Predicates class which uses an enum to enforce a single instance of certain Predicates like alwaysTrue(). It does not expose the enum to users though.
How do I implement subclassable singletons?

How do I implement subclassable singletons?

By : Nithin Raj P
Date : March 29 2020, 07:55 AM
will help you Not sure why you think you need a singleton pattern here, but in any case, you should really be doing this in __new__.
code :
class Singleton(object):

    def __new__(cls):

            return cls._instance
        except AttributeError:
            cls._instance = object.__new__(cls)
            return cls._instance
Using MvvmCross IoC, How can I get a list of singletons that implement a common interface?

Using MvvmCross IoC, How can I get a list of singletons that implement a common interface?

By : Haobo Zhao
Date : March 29 2020, 07:55 AM
hope this fix your issue There's no Api for this in MvxSimpleIocContainer
However, you can easily implement this yourself reflection - simply use reflection to list all the repository-inheriting interfaces and then use Mvx.Resolve to retrieve the singletons which implement those interfaces.
How to implement ORDER BY from a Spring Data JPA GROUP BY query

How to implement ORDER BY from a Spring Data JPA GROUP BY query

By : Zion Joel Lomat
Date : March 29 2020, 07:55 AM
hop of those help? Based on question How to return a custom object from a Spring Data JPA GROUP BY query, my custom query is working, as follows: , Try this:
code :
public class Goleador {

public class PartidaJogador {

    private Goleador jogador;

    private Long gols;


// DTO as Projection
public interface GoleadorWithGols {
    Goleador getGoleador();
    Long getTotalGols()

public interface GoleadorRepo extends JpaRepository<Goleador, Long> {
    @Query("select j as goleador, sum(pj.gols) as totalGols from PartidaJogador pj join pj.jogador j group by j order by totalGols")
    List<GoleadorWithGols> getGoleadores();
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