Descriptor

Component locator based on group, type, kind, name and version of the component.

Description

The Descriptor class provides you with a component locator. This locator is often used in the PipServices toolkit. It locates components using the following fields:

  • Group: package or named group of components, like “pip-services”.
  • Type: logical component type that defines it’s contract, like “persistence” .
  • Kind: physical implementation type, like “mongodb”.
  • Name: unique component name, like “default”.
  • Version: version of the component contract, like “1.0”.

Important points

  • The locator matching can be done by all or only few selected fields.
  • The fields that shall be excluded from the matching must be set to ""* or null.
  • This approach allows to implement many interesting scenarios. For instance:
    • Locate all loggers (match by type and version)
    • Locate persistence components for a microservice (match by group and type)
    • Locate specific component by its name (match by name)

Constructors

Creates a new instance of the descriptor.

Descriptor(String? group, String? type, String? kind, String? name, String? version)

  • group: String? - logical component group
  • type: String? - logical component type or contract
  • kind: String? - component implementation type
  • name: String? - unique component name
  • version: String? - component implementation version

Instance methods

equals

Compares this descriptor to a value. If value is a Descriptor it tries to match them, otherwise the method returns false.

bool equals(value)

  • value: dynamic - value to match against this descriptor.
  • returns: bool - true if the value is matching descriptor and false otherwise.

exactMatch

Matches this descriptor to another descriptor by all fields. No exceptions are made.

bool exactMatch(Descriptor descriptor)

  • descriptor: Descriptor - descriptor to match this one against.
  • returns: bool - true if descriptors match and false otherwise.

getGroup

Gets the component’s logical group.

String? getGroup()

  • returns: String? - component’s logical group

getKind

Gets the component’s implementation type.

String? getKind()

  • returns: String? - component’s implementation type.

getName

Gets the unique component’s name.

String? getName()

  • returns: String? - unique component’s name.

getVersion

Gets the component’s implementation version.

String? getVersion()

  • returns: String? - component’s implementation version.

isComplete

Checks whether all descriptor fields are set. If descriptor has at least one “*” or null field it is considered “incomplete”,

bool isComplete()

  • returns: bool - true if all descriptor fields are defined and false otherwise.

match

Partially matches this descriptor to another descriptor. Fields that contain “*” or null are excluded from the match.

bool match(Descriptor descriptor)

  • descriptor: Descriptor descriptor to match this one against.
  • returns: bool - true if descriptors match and false otherwise

toString

Gets a string representation of the object. The result is a colon-separated list of descriptor fields as “mygroup:connector:aws:default:1.0”

@override

String toString()

  • returns: String - string representation of the object.

Static methods

fromString

Parses colon-separated list of descriptor fields and returns them as a Descriptor.
Throws a ConfigException if the descriptor string is of a wrong format.

static Descriptor? fromString(String? value)

  • value: String? - colon-separated descriptor fields to initialize Descriptor.
  • returns: Descriptor? - newly created Descriptor.

Examples

var locator1 =  Descriptor('mygroup', 'connector', 'aws', 'default', '1.0');
var locator2 = Descriptor.fromString('mygroup:connector:*:*:1.0');

locator1.match(locator2);		// Result: true
locator1.equal(locator2);		// Result: true
locator1.exactMatch(locator2);	// Result: false