Package org.apache.geode.cache.execute

Interface Function<T>

  • All Superinterfaces:
    Identifiable<java.lang.String>, java.io.Serializable
    All Known Implementing Classes:
    CliFunction, FunctionAdapter
    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<T>
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.

    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

    • Method Detail

      • hasResult

        default boolean hasResult()
        Specifies whether the function sends results while executing. The method returns false if no result is expected.

        If this method returns false, ResultCollector.getResult() throws FunctionException.

        If this method 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<T> 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<T>
        Returns:
        string identifying this function
        Since:
        GemFire 6.0

      • 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()

      • getRequiredPermissions

        default java.util.Collection<ResourcePermission> getRequiredPermissions​(java.lang.String regionName)
        Returns the list of ResourcePermission this function requires.

        By default, functions require DATA:WRITE permission. If your function requires other permissions, you will need to override this method.

        Please be as specific as possible when you set the required permissions for your function e.g. if your function reads from a region, it would be good to include the region name in your permission. It's better to return "DATA:READ:regionName" as the required permission other than "DATA:READ", because the latter means only users with read permission on ALL regions can execute your function.

        All the permissions returned from this method will be ANDed together.

        Parameters:
        regionName - the region this function will be executed on. The regionName is optional and will only be present when the function is executed by an onRegion() executor. In other cases, it will be null. This method returns permissions appropriate to the context, independent of the presence of the regionName parameter.
        Returns:
        a collection of ResourcePermissions indicating the permissions required to execute the function.

      • getRequiredPermissions

        default java.util.Collection<ResourcePermission> getRequiredPermissions​(java.lang.String regionName,
                                                                        java.lang.Object args)
        Returns the list of ResourcePermission this function requires.

        By default, functions require DATA:WRITE permission. If your function requires other permissions, you will need to override this method.

        Please be as specific as possible when you set the required permissions for your function e.g. if your function reads from a region, it would be good to include the region name in your permission. It's better to return "DATA:READ:regionName" as the required permission other than "DATA:READ", because the latter means only users with read permission on ALL regions can execute your function.

        All the permissions returned from this method will be ANDed together.

        Parameters:
        regionName - the region this function will be executed on. The regionName is optional and will only be present when the function is executed by an onRegion() executor. In other cases, it will be null. This method returns permissions appropriate to the context, independent of the presence of the regionName parameter.
        args - the arguments to the function.
        Returns:
        a collection of ResourcePermissions indicating the permissions required to execute the function.