[GitHub] [jena] afs commented on a diff in pull request #1898: GH-1897: More control for Fuseki modules setup

["afs (via GitHub)" <gi...@apache.org>]

afs commented on code in PR #1898:
URL: https://github.com/apache/jena/pull/1898#discussion_r1233073974


##########
jena-fuseki2/jena-fuseki-main/src/main/java/org/apache/jena/fuseki/main/sys/FusekiAutoModules.java:
##########
@@ -0,0 +1,230 @@
+/*
+ * 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.fuseki.main.sys;
+
+import java.util.List;
+import java.util.Objects;
+import java.util.ServiceConfigurationError;
+import java.util.ServiceLoader;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+import org.apache.jena.atlas.lib.Lib;
+import org.apache.jena.atlas.lib.Version;
+import org.apache.jena.atlas.logging.FmtLog;
+import org.apache.jena.fuseki.Fuseki;
+import org.apache.jena.fuseki.FusekiConfigException;
+import org.apache.jena.fuseki.main.FusekiServer;
+import org.slf4j.Logger;
+
+/**
+ * Control of {@link FusekiAutoModule} found via {@link ServiceLoader}.
+ */
+public class FusekiAutoModules {
+
+    private static final Logger LOG = Fuseki.serverLog;
+    private static final Object lock = new Object();
+
+    public static final String logLoadingProperty = "fuseki.logLoading";
+    public static final String envLogLoadingProperty = "FUSEKI_LOGLOADING";
+
+    private static boolean allowDiscovery = true;
+    private static boolean enabled = true;
+    private static FusekiModules altFusekiModules = null;
+
+    /*package*/ static boolean logModuleLoading() {
+        return Lib.isPropertyOrEnvVarSetToTrue(logLoadingProperty, envLogLoadingProperty);
+    }
+
+    /*package*/ static Logger logger() {
+        return LOG;
+    }
+
+    /**
+     * Enable/disable discovery of modules using the service loader.
+     * The default is 'enabled'.
+     */
+    public static void enable(boolean setting) {
+        enabled = setting;
+    }
+
+    /** Whether the system loaded modules are enabled. */
+    public static boolean isEnabled() {
+        return enabled;
+    }
+
+    /**
+     * Setup discovery of modules using the service loader.
+     * This replaces any current setup.
+     */
+    public static void setup() {
+        if ( ! isEnabled() )
+            return;
+        // Setup and discover now
+        autoModules = createServiceLoaderModules();
+    }
+
+    /**
+     * Load the the system wide Fuseki modules if it has not already been loaded.
+     * If disabled, return an empty  FusekiModules
+     */
+    public static FusekiModules load() {
+        if ( ! enabled )
+            return FusekiModules.empty();
+        if ( altFusekiModules != null )
+            return altFusekiModules;
+        return getServiceLoaderModules().load();
+    }
+
+    // -- ServiceLoader machinery.
+
+    // testing
+    /*package*/ static void reset() {
+        autoModules = null;
+    }
+
+    /**
+     * Ignore any discovered modules and use the given FusekiModules.
+     * Pass null to clear a previous setting.
+     */
+    static void setSystemDefault(FusekiModules fusekiModules) {
+        altFusekiModules = fusekiModules;
+    }
+
+    // Single auto module controller.
+    private static FusekiServiceLoaderModules autoModules = null;
+
+    private static FusekiServiceLoaderModules getServiceLoaderModules() {
+        if ( autoModules == null )
+            setup();
+        return autoModules;
+    }
+
+    private static FusekiServiceLoaderModules createServiceLoaderModules() {
+        FusekiServiceLoaderModules newAutoModules = new FusekiServiceLoaderModules();
+        newAutoModules.setDiscovery();
+        return newAutoModules;
+    }
+
+    /**
+     * Use {@link java.util.ServiceLoader} to find {@link FusekiModule}
+     * available via the classpath or modules.
+     * <p>
+     * These are the modules used when building a {@link FusekiServer} if
+     * {@link FusekiServer.Builder#setFusekiModules} is not used.
+     */
+    private static class FusekiServiceLoaderModules {
+
+        // This keeps the list of discovered Fuseki modules.
+        private ServiceLoader<FusekiAutoModule> serviceLoader = null;
+
+        private FusekiServiceLoaderModules() { }
+
+        private void setDiscovery() {
+            serviceLoader = discover();
+        }
+
+        /**
+         * Discover FusekiModules via {@link java.util.ServiceLoader}.
+         * This step does not create the module objects.
+         */
+        private ServiceLoader<FusekiAutoModule> discover() {
+            // Look for the 4.8.0 name (FusekiModule) which (4.9.0) is split into
+            // FusekiModule (interface) and FusekiAutoModule (this is loaded by ServiceLoader)
+            // Remove sometime!
+            discoveryWarnLegacy();
+
+            Class<FusekiAutoModule> moduleClass = FusekiAutoModule.class;
+            ServiceLoader<FusekiAutoModule> newServiceLoader = null;
+            synchronized (this) {
+                try {
+                    newServiceLoader = ServiceLoader.load(moduleClass, this.getClass().getClassLoader());
+                } catch (ServiceConfigurationError ex) {
+                    FmtLog.error(LOG, ex, "Problem with service loading for %s", moduleClass.getName());
+                    throw ex;
+                }
+                if ( LOG.isDebugEnabled() ) {
+                    newServiceLoader.stream().forEach(provider->{
+                        FmtLog.info(LOG, "Fuseki Module: %s", provider.type().getSimpleName());
+                    });
+                }
+            }
+            return newServiceLoader;
+        }
+
+        private void discoveryWarnLegacy() {
+            Class<FusekiModule> moduleClass = FusekiModule.class;
+            try {
+                ServiceLoader<FusekiModule> newServiceLoader = ServiceLoader.load(moduleClass, this.getClass().getClassLoader());
+                newServiceLoader.stream().forEach(provider->{
+                    FmtLog.warn(FusekiAutoModules.class, "Legacy: \"%s\" : Interface FusekiModule changed to FusekiAutoModule", provider.type().getSimpleName());

Review Comment:
   Done



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