A resolver provider is a factory for custom implementations of InetAddress resolvers. A resolver defines operations for looking up (resolving) host names and IP addresses.
A resolver provider is a concrete subclass of this class that has a zero-argument constructor and implements the abstract methods specified below.
A given invocation of the Java virtual machine maintains a single
system-wide resolver instance, which is used by
InetAddress. It is set after the VM is fully initialized and when an
invocation of a method in InetAddress
class triggers the first lookup
operation.
A resolver provider is located and loaded by
InetAddress
to create the system-wide resolver as follows:
- The
ServiceLoader
mechanism is used to locate anInetAddressResolverProvider
using the system class loader. The order in which providers are located is implementation specific. The first provider found will be used to instantiate theInetAddressResolver
by invoking theget(InetAddressResolverProvider.Configuration)
method. The returnedInetAddressResolver
will be set as the system-wide resolver. - If the previous step fails to find any resolver provider the built-in resolver will be set as the system-wide resolver.
If instantiating a custom resolver from a provider discovered in step 1 throws an error or exception, the system-wide resolver will not be set and the error or exception will be propagated to the caller of the method that triggered the lookup operation. Otherwise, any lookup operation will be performed using the system-wide resolver.
- Implementation Note:
InetAddress
will use the built-in resolver for any lookup operation that might occur before the VM is fully booted.- Since:
- 18
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic interface
AConfiguration
object is supplied to theget(Configuration)
method when setting the system-wide resolver. -
Constructor Summary
ModifierConstructorDescriptionprotected
Creates a new instance ofInetAddressResolverProvider
. -
Method Summary
Modifier and TypeMethodDescriptionabstract InetAddressResolver
get
(InetAddressResolverProvider.Configuration configuration) Initialize and return anInetAddressResolver
provided by this provider.abstract String
name()
Returns the name of this provider, ornull
if unnamed.
-
Constructor Details
-
InetAddressResolverProvider
protected InetAddressResolverProvider()Creates a new instance ofInetAddressResolverProvider
.- Implementation Note:
- It is recommended that an
InetAddressResolverProvider
service implementation initialization should be as simple as possible, in order to avoid possible risks of deadlock or class loading cycles during the instantiation of the service provider. - Throws:
SecurityException
- if a security manager is present and itscheckPermission
method doesn't allow theRuntimePermission("inetAddressResolverProvider")
.
-
-
Method Details
-
get
Initialize and return anInetAddressResolver
provided by this provider. This method is called byInetAddress
when installing the system-wide resolver implementation.Any error or exception thrown by this method is considered as a failure of
InetAddressResolver
instantiation and will be propagated to the caller of the method that triggered the lookup operation.- Parameters:
configuration
- aInetAddressResolverProvider.Configuration
instance containing platform built-in address resolution configuration.- Returns:
- the resolver provided by this provider
-
name
Returns the name of this provider, ornull
if unnamed.- Returns:
- the name of this provider, or
null
if unnamed
-