Java tutorial
/* * Copyright 2016 The Netty Project * * The Netty Project licenses this file to you under the Apache License, * version 2.0 (the "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at: * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. */ package io.netty.channel.kqueue; import io.netty.channel.unix.FileDescriptor; import io.netty.util.internal.SystemPropertyUtil; import io.netty.util.internal.UnstableApi; /** * If KQueue is available the JNI resources will be loaded when this class loads. */ @UnstableApi public final class KQueue { private static final Throwable UNAVAILABILITY_CAUSE; static { Throwable cause = null; if (SystemPropertyUtil.getBoolean("io.netty.transport.noNative", false)) { cause = new UnsupportedOperationException( "Native transport was explicit disabled with -Dio.netty.transport.noNative=true"); } else { FileDescriptor kqueueFd = null; try { kqueueFd = Native.newKQueue(); } catch (Throwable t) { cause = t; } finally { if (kqueueFd != null) { try { kqueueFd.close(); } catch (Exception ignore) { // ignore } } } } UNAVAILABILITY_CAUSE = cause; } /** * Returns {@code true} if and only if the <a href="https://netty.io/wiki/native-transports.html">{@code * netty-transport-native-kqueue}</a> is available. */ public static boolean isAvailable() { return UNAVAILABILITY_CAUSE == null; } /** * Ensure that <a href="https://netty.io/wiki/native-transports.html">{@code netty-transport-native-kqueue}</a> is * available. * * @throws UnsatisfiedLinkError if unavailable */ public static void ensureAvailability() { if (UNAVAILABILITY_CAUSE != null) { throw (Error) new UnsatisfiedLinkError("failed to load the required native library") .initCause(UNAVAILABILITY_CAUSE); } } /** * Returns the cause of unavailability of <a href="https://netty.io/wiki/native-transports.html">{@code * netty-transport-native-kqueue}</a>. * * @return the cause if unavailable. {@code null} if available. */ public static Throwable unavailabilityCause() { return UNAVAILABILITY_CAUSE; } private KQueue() { } }