java.util
Class ServiceLoader<S>
- Iterable<E>
Facilities for loading service providers. A service is
defined by a set of interfaces or abstract classes, and
a service provider gives a concrete implementation of this.
Service providers may be installed as part of the runtime
environment using JAR files in the extension directories,
or may be simply supplied on the classpath.
In terms of loading a service, the service is defined by
a single interface or abstract class which the provider
implements. This may not constitute the entire service,
but is simply a mechanism by which a provider of the
service can be loaded and its capabilities determined.
The variety of possible services means that no more
requirements are made of the service provider other than
that it must have an accessible zero argument constructor
in order to allow an instance to be created.
Service providers are listed in a file named after the
service type in the directory
META-INF/services.
The file contains a list of classes, and must be encoded
using UTF-8. Whitespace is ignored. Comments can be
included by using a
'#' prefix; anything occurring
on the same line after this symbol is ignored. Duplicate classes
are ignored.
The classes are loaded using the same classloader that was
queried in order to locate the configuration file. As a result,
the providers do not need to reside in the same JAR file as the
resource; they merely have to be accessible to this classloader,
which may differ from the one that loaded the file itself.
Providers are located and instantiated lazily, as calls to the
iterator() are made. Providers are cached, and those in
the cache are returned first. The cache may be cleared by calling
reload(). Service loaders always execute in the security
context of the caller, so ideally calls should be made from a trusted
source.
Note that this class is not thread-safe, and that strange errors may
occur as the result of the use of remote URLs occurring on the classpath,
which lead to erroneous web pages.
static | ServiceLoader load(Class service)- Creates a new service loader for the given service,
using the context class loader of the current thread.
|
static | ServiceLoader load(Class service, ClassLoader loader)- Creates a new service loader for the given service,
using the specified class loader.
|
static | ServiceLoader loadInstalled(Class service)- Creates a new service loader for the given service,
using the extension class loader.
|
Iterator | iterator()- Lazily loads the available providers.
|
void | reload()- Clears the cache of the provider, so that all providers
are again read from the configuration file and instantiated.
|
String | toString()- Returns a textual representation of this
ServiceLoader.
|
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
ServiceLoader load
public static ServiceLoader load(Class service)
Creates a new service loader for the given service,
using the context class loader of the current thread.
This is equivalent to calling ServiceLoader.load(service,
Thread.currentThread().getContextClassLoader()).
service - the interface or abstract class that represents
the service.
ServiceLoader load
public static ServiceLoader load(Class service,
ClassLoader loader)
Creates a new service loader for the given service,
using the specified class loader. The class loader is
used to access the configuration file and the service
provider instances themselves. If the loader is
null, the system class loader (or, if
this is also null, the bootstrap class
loader).
service - the interface or abstract class that represents
the service.loader - the class loader used to load the configuration
file and service providers.
ServiceLoader loadInstalled
public static ServiceLoader loadInstalled(Class service)
Creates a new service loader for the given service,
using the extension class loader. If the extension
class loader can not be found, the system class loader
is used (or, if this is null, the
bootstrap class loader). The primary use of this method
is to only obtain installed services, ignoring any which
may appear on the classpath. This is equivalent to calling
load(service, extClassLoader) where
extClassLoader is the extension class loader
(or null if this is unavailable).
service - the interface or abstract class that represents
the service.
iterator
public Iterator iterator()
Lazily loads the available providers. The iterator first returns
providers from the cache, in instantiation order, followed by any
remaining providers, which are added to the cache after loading.
The actual loading and parsing of the configuration file takes
place in the
Iterator.hasNext() and
Iterator.next()
methods, which means that they may result in a
ServiceConfigurationError being thrown. If such an error
does occur, subsequent invocations will attempt to recover.
The
remove() method is not supported and instead throws
an
UnsupportedOperationException.
- iterator in interface Iterable<E>
- an iterator that lazily loads service providers.
reload
public void reload()
Clears the cache of the provider, so that all providers
are again read from the configuration file and instantiated.
ServiceLoader.java -- Allows loading of plug-in services.
Copyright (C) 2006, 2007 Free Software Foundation
This file is part of GNU Classpath.
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.
Linking this library statically or dynamically with other modules is
making a combined work based on this library. Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module. An independent module is a module which is not derived from
or based on this library. If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so. If you do not wish to do so, delete this
exception statement from your version.