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.

public 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.

public boolean equals(Object value)

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

exactMatch

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

public boolean exactMatch(Descriptor descriptor)

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

getGroup

Gets the component’s logical group.

public String getGroup()

  • returns: String - component’s logical group

getKind

Gets the component’s implementation type.

public String getKind()

  • returns: String - component’s implementation type.

getName

Gets the unique component’s name.

public String getName()

  • returns: String - unique component’s name.

getType

Gets the component’s logical type.

public String getType()

  • returns: String - the component’s logical type.

getVersion

Gets the component’s implementation version.

public 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”,

public boolean isComplete()

  • returns: boolean - 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.

public boolean match(Descriptor descriptor)

  • descriptor: Descriptor descriptor to match this one against.
  • returns: boolean - 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”

public 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.

public static Descriptor fromString(String value) throws ConfigException

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

Examples

{
  Descriptor locator1 = new Descriptor("mygroup", "connector", "aws", "default", "1.0");
  Descriptor locator2 = Descriptor.fromString("mygroup:connector:*:*:1.0");
 
  locator1.match(locator2);        // Result: true
  locator1.equal(locator2);        // Result: true
  locator1.exactMatch(locator2);	// Result: false
  }