add apidoc/etc

sql/src/main/java/org/apache/druid/sql/hook/DruidHook.java

@@ -21,15 +21,13 @@ package org.apache.druid.sql.hook;
 
 import com.google.errorprone.annotations.Immutable;
 import org.apache.calcite.rel.RelNode;
-import org.apache.druid.annotations.SuppressFBWarnings;
-
-import java.io.Closeable;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 
+/**
+ * Interface for hooks that can be invoked by {@link DruidHookDispatcher}.
+ *
+ * HookKey should be added at every place a new hook is needed.
+ */
 @FunctionalInterface
 public interface DruidHook<T>
 {
@@ -74,41 +72,4 @@ public interface DruidHook<T>
   }
 
   void invoke(HookKey<T> key, T object);
-
-  @SuppressFBWarnings({"MS_OOI_PKGPROTECT"})
-  Map<HookKey<?>, List<DruidHook<?>>> GLOBAL = new HashMap<>();
-
-  static void register1(HookKey<?> label, DruidHook<?> hook)
-  {
-    GLOBAL.computeIfAbsent(label, k -> new ArrayList<>()).add(hook);
-  }
-
-  static void unregister1(HookKey<?> key, DruidHook<?> hook)
-  {
-    GLOBAL.get(key).remove(hook);
-  }
-
-  static <T> Closeable withHook1(HookKey<T> key, DruidHook<T> hook)
-  {
-    register1(key, hook);
-    return new Closeable()
-    {
-      @Override
-      public void close()
-      {
-        unregister1(key, hook);
-      }
-    };
-  }
-
-  @SuppressWarnings({"rawtypes", "unchecked"})
-  static <T> void dispatch12(HookKey<T> key, T object)
-  {
-    List<DruidHook<?>> hooks = GLOBAL.get(key);
-    if (hooks != null) {
-      for (DruidHook hook : hooks) {
-        hook.invoke(key, object);
-      }
-    }
-  }
 }

sql/src/main/java/org/apache/druid/sql/hook/DruidHook2.java

@@ -1,24 +0,0 @@
-/*
- * 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.druid.sql.hook;
-
-public interface DruidHook2<T>
-{
-}

sql/src/main/java/org/apache/druid/sql/hook/DruidHookDispatcher.java

@@ -21,6 +21,8 @@ package org.apache.druid.sql.hook;
 
 import com.google.inject.Inject;
 import org.apache.druid.guice.LazySingleton;
+import org.apache.druid.quidem.DruidConnectionExtras;
+import org.apache.druid.sql.calcite.planner.PlannerContext;
 import org.apache.druid.sql.hook.DruidHook.HookKey;
 
 import java.io.Closeable;
@@ -29,24 +31,32 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+/**
+ * Dispatcher for Druid hooks.
+ *
+ * A single instance should live in the system and be used to dispatch hooks.
+ * Usual way to dispatch should be via
+ * {@link PlannerContext#dispatchHook(HookKey, Object)}. Access to this class is
+ * also possible thru {@link DruidConnectionExtras}.
+ */
 @LazySingleton
 public class DruidHookDispatcher
 {
+  Map<HookKey<?>, List<DruidHook<?>>> hooks = new HashMap<>();
+
   @Inject
   public DruidHookDispatcher()
   {
   }
 
-  Map<HookKey<?>, List<DruidHook<?>>> GLOBAL = new HashMap<>();
-
   public void register(HookKey<?> label, DruidHook<?> hook)
   {
-    GLOBAL.computeIfAbsent(label, k -> new ArrayList<>()).add(hook);
+    hooks.computeIfAbsent(label, k -> new ArrayList<>()).add(hook);
   }
 
   public void unregister(HookKey<?> key, DruidHook<?> hook)
   {
-    GLOBAL.get(key).remove(hook);
+    hooks.get(key).remove(hook);
   }
 
   public <T> Closeable withHook(HookKey<T> key, DruidHook<T> hook)
@@ -65,9 +75,9 @@ public class DruidHookDispatcher
   @SuppressWarnings({"rawtypes", "unchecked"})
   public <T> void dispatch(HookKey<T> key, T object)
   {
-    List<DruidHook<?>> hooks = GLOBAL.get(key);
+    List<DruidHook<?>> currentHooks = hooks.get(key);
-    if (hooks != null) {
+    if (currentHooks != null) {
-      for (DruidHook hook : hooks) {
+      for (DruidHook hook : currentHooks) {
         hook.invoke(key, object);
       }
     }