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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;
import com.gemstone.gemfire.cache.Region;
import com.gemstone.gemfire.lang.Identifiable;
/**
* Defines the interface a user defined function implements.
* {@link Function}s can be of different types. Some can have results while others need not return
* any result. Some functions require writing in the targeted {@link Region} while some may just
* be read operations.
* Consider extending {@link FunctionAdapter} which has default values for some of the function attributes.
* Even though this interface extends Serializable, functions will only be serialized if they are not registered.
* For best performance it is recommended that you implement {@link #getId()} to return a non-null identifier
* and register your function using {@link FunctionService#registerFunction(Function)} or the cache.xml function element.
*
* @see FunctionAdapter
* @see FunctionService
*
* @author Yogesh Mahajan
* @author Mitch Thomas
*
* @since 6.0
*/
public interface Function extends Identifiable {
/**
* 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();
/**
* 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 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 String getId();
/**
* 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 Region passed to
* FunctionService#onRegion(com.gemstone.gemfire.cache.Region) is a partitioned region
*
*
* @return false if the function is read only, otherwise returns true
* @since 6.0
* @see FunctionService
*/
public boolean optimizeForWrite();
/**
* 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();
}