Function (Pivotal GemFire 9.0.4)

All Superinterfaces:

Identifiable<java.lang.String>, java.io.Serializable

All Known Implementing Classes:

BootstrappingFunction, CreateRegionFunction, FunctionAdapter, RegionSizeFunction, TouchPartitionedRegionEntriesFunction, TouchReplicatedRegionEntriesFunction

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface Function
extends Identifiable<java.lang.String>
```
Defines the interface a user defined function implements. Functions can be of different types. Some can have results while others need not return any result. Some functions require writing in the targeted Region while some may just be read operations. Consider extending 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 getId() to return a non-null identifier and register your function using FunctionService.registerFunction(Function) or the cache.xml function element.

Since:

GemFire 6.0

See Also:

FunctionAdapter, FunctionService

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method and Description
`void`	`execute(FunctionContext context)` The method which contains the logic to be executed.
`default java.lang.String`	`getId()` Return a unique function identifier, used to register the function with `FunctionService`
`default boolean`	`hasResult()` Specifies whether the function sends results while executing.
`default boolean`	`isHA()` Specifies whether the function is eligible for re-execution (in case of failure).
`default boolean`	`optimizeForWrite()` Return true to indicate to GemFire the method requires optimization for writing the targeted `FunctionService.onRegion(org.apache.geode.cache.Region)` and any associated routing objects.

- Method Detail
  - hasResult
```
default boolean hasResult()
```
    Specifies whether the function sends results while executing. The method returns false if no result is expected.
    
    If hasResult() returns false, ResultCollector.getResult() throws FunctionException.
    
    If hasResult() returns true, ResultCollector.getResult() blocks and waits for the result of function execution
    
    Returns:
    
    whether this function returns a Result back to the caller.
    
    Since:
    
    GemFire 6.0
  - execute
```
void execute(FunctionContext context)
```
    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 Execution. The context provided to this function is the one which was built using 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 RegionFunctionContext.
    
    Parameters:
    
    context - as created by Execution
    
    Since:
    
    GemFire 6.0
  - getId
```
default java.lang.String getId()
```
    Return a unique function identifier, used to register the function with FunctionService
    
    Specified by:
    
    getId in interface Identifiable<java.lang.String>
    
    Returns:
    
    string identifying this function
    
    Since:
    
    GemFire 6.0
  - optimizeForWrite
```
default boolean optimizeForWrite()
```
    Return true to indicate to GemFire the method requires optimization for writing the targeted FunctionService.onRegion(org.apache.geode.cache.Region) and any associated routing objects.
    
    Returning false will optimize for read behavior on the targeted FunctionService.onRegion(org.apache.geode.cache.Region) and any associated routing objects.
    
    This method is only consulted when Region passed to FunctionService#onRegion(org.apache.geode.cache.Region) is a partitioned region
    
    Returns:
    
    false if the function is read only, otherwise returns true
    
    Since:
    
    GemFire 6.0
    
    See Also:
    
    FunctionService
  - isHA
```
default boolean isHA()
```
    Specifies whether the function is eligible for re-execution (in case of failure).
    
    Returns:
    
    whether the function is eligible for re-execution.
    
    Since:
    
    GemFire 6.5
    
    See Also:
    
    FunctionContext.isPossibleDuplicate()

Interface Function

Method Summary

Method Detail

hasResult

execute

getId

optimizeForWrite

isHA