org.apache.brooklyn.api.framework

Class FrameworkLookup

java.lang.Object

org.apache.brooklyn.api.framework.FrameworkLookup

public class FrameworkLookup
extends java.lang.Object

A utility to fetch an instance of a class from either OSGI if available, or by a Service Loader otherwise. The intention of this class is to provide a means to lookup beans in the OSGI service registry that were previously looked up via a ServiceLoader, but still maintain the backward compatible behaviour when not running in an OSGI container. NOTE, when OSGI bundle registry is used, this code performs a BundleContext.getService(). When calling BundleContext.getService() the reference count for the service in question is increased, and without any calls to BundleContext.ungetService() the only moment it will drop to zero is when the client bundle is unloaded, which this code does not do. Therefore this class is not suitable for use in a situation where client code needs to take account of services coming and going, and explicitly avoid using the service when its reference count has gone to zero.

Constructor Summary

Constructors

Constructor and Description
FrameworkLookup()

Method Summary

Modifier and Type	Method and Description
static <T> Maybe<T>	lookup(java.lang.Class<T> clazz) Find an instance of the given class in the framework.
static <T> Maybe<T>	lookup(java.lang.Class<T> clazz, java.lang.ClassLoader loader) Find an instance of the given class in the framework.
static <T> java.lang.Iterable<T>	lookupAll(java.lang.Class<T> clazz) Find all instances of the given class in the framework.
static <T> java.lang.Iterable<T>	lookupAll(java.lang.Class<T> clazz, java.lang.ClassLoader loader) Find all instances of the given class in the framework.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FrameworkLookup

public FrameworkLookup()

Method Detail

lookup

public static <T> Maybe<T> lookup(java.lang.Class<T> clazz)

Find an instance of the given class in the framework. This first performs an OSGI lookup if the OSGI framework is available. If it is not then it falls back to attempting a lookup from the current context classpath via a ServiceLoader.

Type Parameters:

T - The type for the class.

Parameters:

clazz - The class (typically the class of an interface) to search in the framework.

Returns:

A maybe of the instance found in the framework.

lookup

public static <T> Maybe<T> lookup(java.lang.Class<T> clazz,
                                  java.lang.ClassLoader loader)

Find an instance of the given class in the framework. This first performs an OSGI lookup if the OSGI framework is available. If it is not then it falls back to attempting a lookup from the current context classpath via a ServiceLoader.

Type Parameters:

T - The type for the class.

Parameters:

clazz - The class (typically the class of an interface) to search in the framework.

loader - If falling back to ServiceLoader, this class loader is used to load the class. If null, the system class loader (or, failing that, the bootstrap class loader) is used.

Returns:

A maybe of the instance found in the framework.

lookupAll

public static <T> java.lang.Iterable<T> lookupAll(java.lang.Class<T> clazz)

Find all instances of the given class in the framework. This first performs an OSGI lookup if the OSGI framework is available. If it is not then it falls back to attempting a lookup from the current context classpath via a ServiceLoader.

Type Parameters:

T - The type for the class.

Parameters:

clazz - The class (typically the class of an interface) to search in the framework.

Returns:

An iterable over the instances found in the framework.

lookupAll

public static <T> java.lang.Iterable<T> lookupAll(java.lang.Class<T> clazz,
                                                  java.lang.ClassLoader loader)

Find all instances of the given class in the framework. This first performs an OSGI lookup if the OSGI framework is available. If it is not then it falls back to attempting a lookup from the current context classpath via a ServiceLoader.

Type Parameters:

T - The type for the class.

Parameters:

clazz - The class (typically the class of an interface) to search in the framework.

loader - If falling back to ServiceLoader, this class loader is used to load the class. If null, the system class loader (or, failing that, the bootstrap class loader) is used.

Returns:

An iterable over the instances found in the framework.