content: /*
   * 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.calcite.server;
  
  import org.apache.calcite.jdbc.CalcitePrepare;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.util.ReflectUtil;
  import org.apache.calcite.util.ReflectiveVisitor;
  
  /** Abstract implementation of {@link org.apache.calcite.server.DdlExecutor}. */
  public class DdlExecutorImpl implements DdlExecutor, ReflectiveVisitor {
    /** Creates a DdlExecutorImpl.
     * Protected only to allow sub-classing;
     * use a singleton instance where possible. */
    protected DdlExecutorImpl() {
    }
  
    /** Dispatches calls to the appropriate method based on the type of the
     * first argument. */
    @SuppressWarnings({"method.invocation.invalid", "argument.type.incompatible"})
    private final ReflectUtil.MethodDispatcher<Void> dispatcher =
        ReflectUtil.createMethodDispatcher(void.class, this, "execute",
            SqlNode.class, CalcitePrepare.Context.class);
  
    @Override public void executeDdl(CalcitePrepare.Context context,
        SqlNode node) {
      dispatcher.invoke(node, context);
    }
  
    /** Template for methods that execute DDL commands.
     *
     * <p>The base implementation throws {@link UnsupportedOperationException}
     * because a {@link SqlNode} is not DDL, but overloaded methods such as
     * {@code public void execute(SqlCreateFoo, CalcitePrepare.Context)} are
     * called via reflection. */
    public void execute(SqlNode node, CalcitePrepare.Context context) {
      throw new UnsupportedOperationException("DDL not supported: " + node);
    }
  }
  