groovy.lang

Annotation Type Singleton

@Documented
@Retention(value=SOURCE)
@Target(value=TYPE)
public @interface Singleton

Class annotation to make a singleton class. The singleton is obtained through normal property access using the singleton property (defaults to "instance"). Such classes can be initialized during normal static initialization of the class or lazily (on first access). To make the singleton lazy use @Singleton(lazy=true). Lazy singletons are implemented with double-checked locking and a volatile backing field. By default, no explicit constructors are allowed. To create one or more explicit constructors use @Singleton(strict=false). This could be used to:

• provide your own custom initialization logic in your own no-arg constructor - you will be responsible for the entire code (the @Singleton annotation becomes merely documentation)
• provide one or more constructors with arguments for a quasi-singleton - these constructors will be used to create instances that are independent of the singleton instance returned by the singleton property

Author:

Alex Tkachman, Paul King

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
boolean	lazy
String	property
boolean	strict

Element Detail

lazy

public abstract boolean lazy

Returns:

if this singleton should be lazy

Default:

false

strict

public abstract boolean strict

Returns:

if this singleton should have strict semantics

Default:

true

property

public abstract String property

Returns:

the singleton property name

Default:

"instance"