Github user sjcorbett commented on a diff in the pull request:
https://github.com/apache/incubator-brooklyn/pull/955#discussion_r42049781
--- Diff:
core/src/main/java/org/apache/brooklyn/core/resolve/ServiceSpecResolver.java ---
@@ -0,0 +1,55 @@
+/*
+ * 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.brooklyn.core.resolve;
+
+import java.util.ServiceLoader;
+import java.util.Set;
+
+import javax.annotation.Nullable;
+
+import org.apache.brooklyn.api.entity.EntitySpec;
+import org.apache.brooklyn.core.mgmt.ManagementContextInjectable;
+import
org.apache.brooklyn.core.mgmt.classloading.BrooklynClassLoadingContext;
+
+/**
+ * Resolves and decorates {@link EntitySpec entity specifications} based
on the {@code serviceType} in a template.
+ * <p>
+ * The resolver implementation will use the rest of the local part of the
service type information
+ * to create and decorate an appropriate {@link EntitySpec entity}.
+ * <p>
+ * The resolvers are loaded using the {@link ServiceLoader} mechanism,
allowing external libraries
+ * to add extra service type implementations that will be picked up at
runtime.
+ */
+public interface ServiceSpecResolver extends ManagementContextInjectable {
+ /**
+ * Uniquely identifies the resolver, can be used to address the same
resolver at a later point in time.
+ * For implementations: this usually matches the service type prefix,
but not required.
+ */
+ String getName();
+
+ /**
+ * @return if the resolver can create a spec for the service type
+ */
+ boolean accepts(String type, BrooklynClassLoadingContext loader);
+
+ /**
+ * Create a spec for the service type
+ */
+ @Nullable EntitySpec<?> resolve(String type,
BrooklynClassLoadingContext loader, Set<String> encounteredTypes);
--- End diff --
Might be useful to note in the documentation what implementors should do
with `encounteredTypes` and what a `null` return value indicates.
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