java.lang.Object | |
↳ | java.util.ServiceLoader<S> |
A service-provider loader.
A service provider is a factory for creating all known implementations of a particular
class or interface S
. The known implementations are read from a configuration file in
META-INF/services/
. The file's name should match the class' binary name (such as
java.util.Outer$Inner
).
The file format is as follows.
The file's character encoding must be UTF-8.
Whitespace is ignored, and #
is used to begin a comment that continues to the
next newline.
Lines that are empty after comment removal and whitespace trimming are ignored.
Otherwise, each line contains the binary name of one implementation class.
Duplicate entries are ignored, but entries are otherwise returned in order (that is, the file
is treated as an ordered set).
Given these classes:
package a.b.c; public interface MyService { ... } public class MyImpl1 implements MyService { ... } public class MyImpl2 implements MyService { ... }And this configuration file (stored as
META-INF/services/a.b.c.MyService
):
# Known MyService providers. a.b.c.MyImpl1 # The original implementation for handling "bar"s. a.b.c.MyImpl2 # A later implementation for "foo"s.You might use
ServiceProvider
something like this:
for (MyService service : ServiceLoader.load(MyService.class)) { if (service.supports(o)) { return service.handle(o); } }
Note that each iteration creates new instances of the various service implementations, so
any heavily-used code will likely want to cache the known implementations itself and reuse them.
Note also that the candidate classes are instantiated lazily as you call next
on the
iterator: construction of the iterator itself does not instantiate any of the providers.
Public Methods | |||||||||||
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Returns an iterator over all the service providers offered by this service loader.
| |||||||||||
Constructs a service loader.
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Constructs a service loader, using the current thread's context class loader.
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Constructs a service loader, using the extension class loader.
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Invalidates the cache of known service provider class names.
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Returns a string containing a concise, human-readable description of this
object.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
| |||||||||||
From interface
java.lang.Iterable
|
Returns an iterator over all the service providers offered by this service loader.
Note that hasNext
and next
may throw if the configuration is invalid.
Each iterator will return new instances of the classes it iterates over, so callers may want to cache the results of a single call to this method rather than call it repeatedly.
The returned iterator does not support remove
.
Iterator
instance.
Constructs a service loader. If classLoader
is null, the system class loader
is used.
service | the service class or interface |
---|---|
classLoader | the class loader |
Constructs a service loader, using the current thread's context class loader.
service | the service class or interface |
---|
Constructs a service loader, using the extension class loader.
service | the service class or interface |
---|
Invalidates the cache of known service provider class names.
Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
See Writing a useful
toString
method
if you intend implementing your own toString
method.