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8244202: Implementation of JEP 418: Internet-Address Resolution SPI

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Co-authored-by: Chris Hegarty <chegar@openjdk.org>
Co-authored-by: Daniel Fuchs <dfuchs@openjdk.org>
Co-authored-by: Alan Bateman <alanb@openjdk.org>
Reviewed-by: dfuchs, alanb, michaelm, chegar
This commit is contained in:
Aleksei Efimov 2021-11-11 14:33:58 +00:00
parent c29cab8ab4
commit 2ca4ff87b7
56 changed files with 2986 additions and 293 deletions
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src/java.base/share/classes/java/net/spi/InetAddressResolverProvider.java Normal file
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/*
* Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.net.spi;
import sun.net.ResolverProviderConfiguration;
import java.net.InetAddress;
import java.util.ServiceLoader;
/**
* Service-provider class for {@linkplain InetAddressResolver InetAddress resolvers}.
*
* <p> A resolver provider is a factory for custom implementations of {@linkplain
* InetAddressResolver InetAddress resolvers}. A resolver defines operations for
* looking up (resolving) host names and IP addresses.
* <p>A resolver provider is a concrete subclass of this class that has a
* zero-argument constructor and implements the abstract methods specified below.
*
* <p> A given invocation of the Java virtual machine maintains a single
* system-wide resolver instance, which is used by
* <a href="{@docRoot}/java.base/java/net/InetAddress.html#host-name-resolution">
* InetAddress</a>. It is set after the VM is fully initialized and when an
* invocation of a method in {@link InetAddress} class triggers the first lookup
* operation.
*
* <p id="system-wide-resolver"> A resolver provider is located and loaded by
* {@link InetAddress} to create the system-wide resolver as follows:
* <ol>
* <li>The {@link ServiceLoader} mechanism is used to locate an
* {@code InetAddressResolverProvider} using the
* system class loader. The order in which providers are located is
* {@linkplain ServiceLoader#load(java.lang.Class, java.lang.ClassLoader)
* implementation specific}.
* The first provider found will be used to instantiate the
* {@link InetAddressResolver InetAddressResolver} by invoking the
* {@link InetAddressResolverProvider#get(InetAddressResolverProvider.Configuration)}
* method. The returned {@code InetAddressResolver} will be set as the
* system-wide resolver.
* <li>If the previous step fails to find any resolver provider the
* <a href="{@docRoot}/java.base/java/net/InetAddress.html#built-in-resolver">
* built-in resolver</a> will be set as the system-wide resolver.
* </ol>
*
* <p> 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 calling thread.
* Otherwise, any lookup operation will be performed using the
* <i>system-wide resolver</i>.
*
* @implNote {@link InetAddress} will use the <i>built-in resolver</i> for any lookup operation
* that might occur before the VM is fully booted.
*
* @since 18
*/
public abstract class InetAddressResolverProvider {
/**
* Initialize and return an {@link InetAddressResolver} provided by
* this provider. This method is called by {@link InetAddress} when
* <a href="#system-wide-resolver">installing</a>
* the system-wide resolver implementation.
*
* <p> Any error or exception thrown by this method is considered as
* a failure of {@code InetAddressResolver} instantiation and will be propagated to
* the calling thread.
* @param configuration a {@link Configuration} instance containing platform built-in address
* resolution configuration.
* @return the resolver provided by this provider
*/
public abstract InetAddressResolver get(Configuration configuration);
/**
* {@return the name of this provider, or {@code null} if unnamed}
*/
public abstract String name();
/**
* The {@code RuntimePermission("inetAddressResolverProvider")} is
* necessary to subclass and instantiate the {@code InetAddressResolverProvider} class,
* as well as to obtain resolver from an instance of that class,
* and it is also required to obtain the operating system name resolution configurations.
*/
private static final RuntimePermission INET_ADDRESS_RESOLVER_PERMISSION =
new RuntimePermission("inetAddressResolverProvider");
/**
* Creates a new instance of {@code InetAddressResolverProvider}.
*
* @throws SecurityException if a security manager is present and its
* {@code checkPermission} method doesn't allow the
* {@code RuntimePermission("inetAddressResolverProvider")}.
* @implNote It is recommended that an {@code 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.
*/
protected InetAddressResolverProvider() {
this(checkPermission());
}
private InetAddressResolverProvider(Void unused) {
}
@SuppressWarnings("removal")
private static Void checkPermission() {
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(INET_ADDRESS_RESOLVER_PERMISSION);
}
return null;
}
/**
* A {@code Configuration} object is supplied to the
* {@link InetAddressResolverProvider#get(Configuration)} method when
* setting the system-wide resolver.
* A resolver implementation can then delegate to the built-in resolver
* provided by this interface if it needs to.
*
* @since 18
*/
public sealed interface Configuration permits ResolverProviderConfiguration {
/**
* Returns the built-in {@linkplain InetAddressResolver resolver}.
*
* @return the JDK built-in resolver.
*/
InetAddressResolver builtinResolver();
/**
* Reads the localhost name from the system configuration.
*
* @return the localhost name.
*/
String lookupLocalHostName();
}
}