diff --git a/jena-core/src/main/java/org/apache/jena/sys/JenaSystem.java b/jena-core/src/main/java/org/apache/jena/sys/JenaSystem.java index 09871f83b96..10aa64dc027 100644 --- a/jena-core/src/main/java/org/apache/jena/sys/JenaSystem.java +++ b/jena-core/src/main/java/org/apache/jena/sys/JenaSystem.java @@ -66,7 +66,8 @@ public JenaSystem() { } * to avoid the risk of recursive initialization. */ public static boolean DEBUG_INIT = false ; - private static volatile boolean initialized = false ; + private static volatile boolean IS_INITIALIZING = false; + private static volatile long ID_OF_INIT_THREAD = -1; /** Output a debugging message if DEBUG_INIT is set */ public static void logLifecycle(String fmt, Object ...args) { @@ -76,22 +77,34 @@ public static void logLifecycle(String fmt, Object ...args) { System.err.println() ; } + /** + * Initialization-on-demand holder idiom + * @see Initialization-on-demand holder idiom + * + */ + private static class LazyHolder { + static final boolean initialized = initialize(); + } + public static void init() { - // Once jena is initialized, all calls are an immediate return. - if ( initialized ) - return ; - // Overlapping attempts to perform initialization will block on the synchronized. - synchronized(JenaSystem.class) { - if ( initialized ) - return ; - setup(); - if ( DEBUG_INIT ) - singleton.debug(DEBUG_INIT); - singleton.initialize(); - singleton.debug(false); - // Last so overlapping initialization waits on the synchronized - initialized = true; + if(IS_INITIALIZING && ID_OF_INIT_THREAD != Thread.currentThread().getId()) { + throw new ExceptionInInitializerError("Jena is already is being initialized by another thread. Please ensure that JenaSystem.init() is called before working with multiple threads."); } + + // Access the initialized flag to trigger class loading + boolean init = LazyHolder.initialized; + } + + private static boolean initialize() { + IS_INITIALIZING = true; + ID_OF_INIT_THREAD = Thread.currentThread().getId(); + setup(); + if ( DEBUG_INIT ) + singleton.debug(DEBUG_INIT); + singleton.initialize(); + singleton.debug(false); + IS_INITIALIZING = false; + return true; } public static void shutdown() { singleton.shutdown(); } diff --git a/jena-integration-tests/src/test/java/org/apache/jena/sys/TS_Sys.java b/jena-integration-tests/src/test/java/org/apache/jena/sys/TS_Sys.java new file mode 100644 index 00000000000..9826dd48d10 --- /dev/null +++ b/jena-integration-tests/src/test/java/org/apache/jena/sys/TS_Sys.java @@ -0,0 +1,30 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF 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 org.apache.jena.sys; + +import org.apache.jena.sparql.exec.http.*; +import org.junit.runner.RunWith; +import org.junit.runners.Suite; + +@RunWith(Suite.class) +@Suite.SuiteClasses( + { TestJenaSystem.class + }) + +public class TS_Sys { } diff --git a/jena-integration-tests/src/test/java/org/apache/jena/sys/TestJenaSystem.java b/jena-integration-tests/src/test/java/org/apache/jena/sys/TestJenaSystem.java new file mode 100644 index 00000000000..56221a8fee7 --- /dev/null +++ b/jena-integration-tests/src/test/java/org/apache/jena/sys/TestJenaSystem.java @@ -0,0 +1,69 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF 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 org.apache.jena.sys; + +import org.apache.jena.rdf.model.ModelFactory; +import org.junit.Test; + + +import java.time.Duration; +import java.time.temporal.ChronoUnit; +import java.util.HashSet; +import java.util.concurrent.Executors; +import java.util.stream.IntStream; + +import static org.junit.jupiter.api.Assertions.*; + +public class TestJenaSystem { + + @Test + public void testInit() { + assertDoesNotThrow(() -> JenaSystem.init()); + } + + @Test + public void testInitParallel() { + + // it is mandatory to init JenaSystem before running anything in parallel + JenaSystem.init(); + + var pool = Executors.newFixedThreadPool(8); + + var futures = IntStream.range(0, 16) + .mapToObj(i -> pool.submit(() -> { + if (i % 2 == 0) + ModelFactory.createDefaultModel(); + else + JenaSystem.init(); + + return i; + })) + .toList(); + + var intSet = new HashSet(); + assertTimeoutPreemptively( + Duration.of(5, ChronoUnit.SECONDS), + () -> { + for (var future : futures) { + intSet.add(future.get()); + } + }); + + assertEquals(16, intSet.size()); + } +}