[isis] branch master updated: ISIS-1841 Internal API: introduce _Plugin for plugin loading

[ah...@apache.org]

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ahuber pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/isis.git


The following commit(s) were added to refs/heads/master by this push:
     new 4bb8ca1  ISIS-1841 Internal API: introduce _Plugin for plugin loading
4bb8ca1 is described below

commit 4bb8ca1ca4148a8cb50dfdad765c4813ae51cd94
Author: Andi Huber <ah...@apache.org>
AuthorDate: Wed Feb 28 09:19:47 2018 +0100

    ISIS-1841 Internal API: introduce _Plugin for plugin loading
    
    Utilizes the Java 7+ service-provider loading facility
---
 .../isis/applib/internal/collections/_Sets.java    | 12 ++++
 .../isis/applib/internal/context/_Plugin.java      | 67 ++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/core/applib/src/main/java/org/apache/isis/applib/internal/collections/_Sets.java b/core/applib/src/main/java/org/apache/isis/applib/internal/collections/_Sets.java
index 194ea33..c8067fc 100644
--- a/core/applib/src/main/java/org/apache/isis/applib/internal/collections/_Sets.java
+++ b/core/applib/src/main/java/org/apache/isis/applib/internal/collections/_Sets.java
@@ -27,10 +27,13 @@ import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentHashMap.KeySetView;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import javax.annotation.Nullable;
 
+import org.apache.isis.applib.internal.base._NullSafe;
+
 /**
  * <h1>- internal use only -</h1>
  * <p>
@@ -64,6 +67,15 @@ public final class _Sets {
 		return Collections.unmodifiableSet(setPreservingOrder);
 	}
 	
+	public static <T> Set<T> unmodifiable(Iterable<T> iterable) {
+		if(iterable==null) {
+			return Collections.emptySet();
+		}
+		return Collections.unmodifiableSet(
+				_NullSafe.stream(iterable)
+				.collect(Collectors.toSet()));
+	}
+	
 	// -- HASH SET
 	
 	public static <T> HashSet<T> newHashSet() {
diff --git a/core/applib/src/main/java/org/apache/isis/applib/internal/context/_Plugin.java b/core/applib/src/main/java/org/apache/isis/applib/internal/context/_Plugin.java
new file mode 100644
index 0000000..5f9a043
--- /dev/null
+++ b/core/applib/src/main/java/org/apache/isis/applib/internal/context/_Plugin.java
@@ -0,0 +1,67 @@
+/*
+ *  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.isis.applib.internal.context;
+
+import java.util.Objects;
+import java.util.ServiceLoader;
+import java.util.Set;
+
+import org.apache.isis.applib.internal.collections._Sets;
+
+/**
+ * <h1>- internal use only -</h1>
+ * <p>
+ * Utilizes the Java 7+ service-provider loading facility.<br/>
+ * see {@link java.util.ServiceLoader}
+ * </p>
+ * <p>
+ * <b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this package! <br/> 
+ * These may be changed or removed without notice!
+ * </p>
+ * @since 2.0.0
+ */
+public final class _Plugin {
+
+	private _Plugin(){}
+	
+	/**
+	 * Returns all services implementing the interface or abstract class representing the {@code service}.
+	 * <p>
+	 * If com.example.impl.StandardCodecs is an implementation of the CodecSet service then its jar file also contains a file named
+	 * <pre>
+	 *      META-INF/services/com.example.CodecSet
+	 * </pre>     
+	 * This file contains the single line:
+	 * <pre>     
+	 *       com.example.impl.StandardCodecs  # Standard codecs
+	 * </pre>
+	 * </p>
+	 * @param service
+	 * @return non null
+	 */
+	public static <S> Set<S> load(Class<S> service){
+		Objects.requireNonNull(service);
+
+		ServiceLoader<S> loader = ServiceLoader.load(service, _Context.getDefaultClassLoader());
+		
+		return _Sets.unmodifiable(loader);   
+	}
+	
+}

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