nl.topicus.jdbc.shaded.io.grpc.ServerProvider Maven / Gradle / Ivy
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/*
* Copyright 2015, Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
*
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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package nl.topicus.jdbc.shaded.io.grpc;
import nl.topicus.jdbc.shaded.com.google.nl.topicus.jdbc.shaded.com.on.annotations.VisibleForTesting;
import nl.topicus.jdbc.shaded.io.grpc.ManagedChannelProvider.ProviderNotFoundException;
import java.util.ServiceLoader;
/**
* Provider of servers for transport agnostic consumption.
*
* Implementations should not throw. If they do, it may interrupt class loading. If
* exceptions may reasonably occur for implementation-specific reasons, implementations should
* generally handle the exception gracefully and return {@code false} from {@link #isAvailable()}.
*/
@Internal
public abstract class ServerProvider {
private static final ServerProvider provider =
load(Thread.currentThread().getContextClassLoader());
@VisibleForTesting
static final ServerProvider load(ClassLoader cl) {
ServiceLoader providers = ServiceLoader.load(ServerProvider.class, cl);
ServerProvider best = null;
for (ServerProvider current : providers) {
if (!current.isAvailable()) {
continue;
} else if (best == null) {
best = current;
} else if (current.priority() > best.priority()) {
best = current;
}
}
return best;
}
/**
* Returns the ClassLoader-wide default server.
*
* @throws ProviderNotFoundException if no provider is available
*/
public static ServerProvider provider() {
if (provider == null) {
throw new ProviderNotFoundException("No functional server found. "
+ "Try adding a dependency on the grpc-nl.topicus.jdbc.shaded.net.y artifact");
}
return provider;
}
/**
* Whether this provider is available for use, taking the current environment into consideration.
* If {@code false}, no other methods are safe to be called.
*/
protected abstract boolean isAvailable();
/**
* A priority, from 0 to 10 that this provider should be used, taking the current environment into
* consideration. 5 should be considered the default, and then tweaked based on environment
* detection. A priority of 0 does not imply that the provider wouldn't work; just that it should
* be last in line.
*/
protected abstract int priority();
/**
* Creates a new builder with the given port.
*/
protected abstract ServerBuilder builderForPort(int port);
}