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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * Licensed 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.cache.execute;

/**
 * Application developers can extend this class instead of implementing the
 * {@link Function} interface.
 * 
 * 
 * This implementation provides the following defaults
 * 
 * 
 * {@link Function#hasResult()} returns true
 * {@link Function#optimizeForWrite()} returns false
 * {@link Function#isHA()} returns true
 * 
 * 
 * 
 * @author Yogesh Mahajan
 * @since 6.0
 * @see Function
 * 
 */
public abstract class FunctionAdapter implements Function {
  /**
   * The method which contains the logic to be executed. This method should be
   * thread safe and may be invoked more than once on a given member for a
   * single {@link Execution}. The context provided to this function is the one
   * which was built using {@linkplain Execution}. The contexts can be data
   * dependent or data-independent so user should check to see if the context
   * provided in parameter is instance of {@link RegionFunctionContext}.
   * 
   * @param context
   *          as created by {@link Execution}
   * @since 6.0
   */
  public abstract void execute(FunctionContext context);

  /**
   * Return a unique function identifier, used to register the function with
   * {@link FunctionService}
   * 
   * @return string identifying this function
   * @since 6.0
   */
  public abstract String getId();

  /**
   * Specifies whether the function sends results while executing. The method
   * returns false if no result is expected.

   * 
   * If {@link Function#hasResult()} returns false,
   * {@link ResultCollector#getResult()} throws {@link FunctionException}.
   * 
   * 
   * If {@link Function#hasResult()} returns true,
   * {@link ResultCollector#getResult()} blocks and waits for the result of
   * function execution
   * 
   * 
   * @return whether this function returns a Result back to the caller.
   * @since 6.0
   */
  public boolean hasResult() {
    return true;
  }

  /**
   * 
   * Return true to indicate to GemFire the method requires optimization for
   * writing the targeted
   * {@link FunctionService#onRegion(com.gemstone.gemfire.cache.Region)} and any
   * associated {@linkplain Execution#withFilter(java.util.Set) routing objects}
   * .
   * 
   * 
   * 
   * Returning false will optimize for read behavior on the targeted
   * {@link FunctionService#onRegion(com.gemstone.gemfire.cache.Region)} and any
   * associated {@linkplain Execution#withFilter(java.util.Set) routing objects}
   * .
   * 
   * 
   * 
   * This method is only consulted when invoked as a
   * {@linkplain FunctionService#onRegion(com.gemstone.gemfire.cache.Region)
   * data dependent function}
   * 
   * 
   * @return false if the function is read only, otherwise returns true
   * @since 6.0
   * @see FunctionService
   */
  public boolean optimizeForWrite() {
    return false;
  }

  /**
   * Specifies whether the function is eligible for re-execution (in case of
   * failure).
   * 
   * @return whether the function is eligible for re-execution.
   * @see RegionFunctionContext#isPossibleDuplicate()
   * 
   * @since 6.5
   */
  public boolean isHA() {
    return true;
  }
}