DependencyResolver

Helper class for resolving component dependencies.

Implements: IReferenceable, IReconfigurable

Description

The DependencyResolver is a helper class that allows you to resolve component dependencies. It is configured to resolve named dependencies by a specific locator.

Important points:

  • During deployment the dependency locator can be changed. This mechanism can be used to clarify a specific dependency among several alternatives. Typically components are configured to retrieve the first dependency that matches a logical group, type and version. However, if the container contains more than one instance and the resolution has to be specific about those instances; they can be given a unique name, and the dependency resolvers can be reconfigured to retrieve dependencies according to their name.

Configuration parameters

  • dependencies:
    • [dependency name 1]: Dependency 1 locator (descriptor)
    • [dependency name N]: Dependency N locator (descriptor)

References

References must match configured dependencies.

Constructors

Creates a new instance of the dependency resolver.

See ConfigParams, IReferences

public constructor(config?: ConfigParams, references?: IReferences)

  • config: ConfigParams - (optional) default configuration where key is dependency name and value is locator (descriptor)
  • references: IReferences - (optional) default component references

Instance methods

configure

Configures the component with specified parameters.

public configure(config: ConfigParams): void

find

Finds all matching dependencies by their name.

public find<T>(name: string, required: boolean): T[]

  • name: string - the dependency name to locate.
  • required: boolean - true to raise an exception when no dependencies are found.
  • returns: T[] - a list of found dependencies

getOneOptional

Gets one optional dependency by its name.

public getOneOptional<T>(name: string): T

  • name: string - the dependency name to locate.
  • returns: T - a dependency reference or null of the dependency was not found

getOneRequired

Gets one required dependency by its name. At least one dependency must present. If the dependency was found it throws a ReferenceException

public getOneRequired<T>(name: string): T

  • name: string - the dependency name to locate.
  • returns: T - a dependency reference

getOptional

Gets all optional dependencies by their name.

public getOptional<T>(name: string): T[]

  • name: string - the dependency name to locate.
  • returns: T[] - a list with found dependencies or empty list of no dependencies was found.

getRequired

Gets all required dependencies by their name. At least one dependency must be present. If no dependencies was found it throws a ReferenceException

public getRequired<T>(name: string): T[]

  • name: string - the dependency name to locate.
  • returns: T[] - a list with found dependencies.

put

Adds a new dependency into this resolver.

public put(name: string, locator: any): void

  • name: string - the dependency’s name.
  • locator: any - the locator to find the dependency by.

setReferences

Sets the component references. References must match configured dependencies.

public setReferences(references: IReferences): void

Static methods

fromTuples

Creates a new DependencyResolver from a list of key-value pairs called tuples where key is dependency name and value the depedency locator (descriptor).

public static fromTuples(…tuples: any[]): DependencyResolver

  • tuples: any[] - a list of values where odd elements are dependency name and the following even elements are dependency locator (descriptor)
  • returns: DependencyResolver - a newly created DependencyResolver.

Examples

class MyComponent: IConfigurable, IReferenceable {
    private _dependencyResolver: DependencyResolver = new DependencyResolver();
    private _persistence: IMyPersistence;
    ...
    
    public constructor() {
        this._dependencyResolver.put("persistence", new Descriptor("mygroup", "persistence", "*", "*", "1.0"));
    }
    
    public configure(config: ConfigParams): void {
        this._dependencyResolver.configure(config);
    }  
    
    public setReferences(references: IReferences): void {
        this._dependencyResolver.setReferences(references);
        this._persistence = this._dependencyResolver.getOneRequired<IMyPersistence>("persistence");
    }
}
     
// Create mycomponent and set specific dependency out of many
let component = new MyComponent();
component.configure(ConfigParams.fromTuples(
    "dependencies.persistence", "mygroup:persistence:*:persistence2:1.0" 
// Override default persistence dependency
));
component.setReferences(References.fromTuples(
    new Descriptor("mygroup","persistence","*","persistence1","1.0"), new MyPersistence(),
    new Descriptor("mygroup","persistence","*","persistence2","1.0"), new MyPersistence()  
// This dependency shall be set
));

See also