Package org.apache.sis.feature

Class AbstractOperation

  • All Implemented Interfaces:
    Serializable, Bi­Function<Abstract­Feature,​Parameter­Value­Group,​Object>, Deprecable
    public abstract class AbstractOperation
extends AbstractIdentifiedType
implements BiFunction<AbstractFeature,​ParameterValueGroup,​Object>
    Describes the behaviour of a feature type as a function or a method. Operations can:
    • Compute values from the attributes.
    • Perform actions that change the attribute values.
    Example: a mutator operation may raise the height of a dam. This changes may affect other properties like the watercourse and the reservoir associated with the dam.
    The value is computed, or the operation is executed, by apply(Feature, Parameter­Value­Group). If the value is modifiable, new value can be set by call to Attribute​.set­Value(Object).
    Warning: this class is experimental and may change after we gained more experience on this aspect of ISO 19109.
    Since:
    0.6
    See Also:
    Default­Feature­Type, Serialized Form

    Defined in the sis-feature module

    • Method Detail

      • getParameters

        public abstract ParameterDescriptorGroup getParameters()
        Returns a description of the input parameters.
        Returns:
        description of the input parameters.

      • getResult

        public abstract AbstractIdentifiedType getResult()
        Returns the expected result type, or null if none.
        Warning: In a future SIS version, the return type may be changed to org​.opengis​.feature​.Identified­Type. This change is pending GeoAPI revision.
        Returns:
        the type of the result, or null if none.

      • apply

        public abstract Object apply​(AbstractFeature feature,
                             ParameterValueGroup parameters)
        Executes the operation on the specified feature with the specified parameters. The value returned by this method depends on the value returned by get­Result():
        • If get­Result() returns null, then this method should return null.
        • If get­Result() returns an instance of Attribute­Type, then this method shall return an instance of Attribute and the Attribute​.get­Type() == get­Result() relation should hold.
        • If get­Result() returns an instance of Feature­Association­Role, then this method shall return an instance of Feature­Association and the Feature­Association​.get­Role() == get­Result() relation should hold.
        Analogy: if we compare Operation to Method in the Java language, then this method is equivalent to Method​.invoke(Object, Object...). The Feature argument is equivalent to this in the Java language, and may be null if the operation does not need a feature instance (like static methods in the Java language).
        Warning: In a future SIS version, the parameter type and return value may be changed to org​.opengis​.feature​.Feature and org​.opengis​.feature​.Property respectively. This change is pending GeoAPI revision.
        Specified by:
        apply in interface Bi­Function<Abstract­Feature,​Parameter­Value­Group,​Object>
        Parameters:
        feature - the feature on which to execute the operation. Can be null if the operation does not need feature instance.
        parameters - the parameters to use for executing the operation. Can be null if the operation does not take any parameters.
        Returns:
        the operation result, or null if this operation does not produce any result.

      • getDependencies

        public Set<String> getDependencies()
        Returns the names of feature properties that this operation needs for performing its task. This method does not resolve transitive dependencies, i.e. if a dependency is itself an operation having other dependencies, the returned set will contain the name of that operation but not the names of that operation dependencies (unless they are the same that the direct dependencies of this).
        Rational: this information is needed for writing the SELECT SQL statement to send to a database server. The requested columns will typically be all attributes declared in a Feature­Type, but also any additional columns needed for the operation while not necessarily included in the Feature­Type.
        The default implementation returns an empty set.
        Returns:
        the names of feature properties needed by this operation for performing its task.

      • equals

        public boolean equals​(Object obj)
        Compares this operation with the given object for equality. The default implementation compares the parameters descriptor and result type.
        Overrides:
        equals in class Abstract­Identified­Type
        Parameters:
        obj - the object to compare with this type.
        Returns:
        true if the given object is equals to this type.

      • toString

        public String toString()
        Returns a string representation of this operation. The returned string is for debugging purpose and may change in any future SIS version.
        Overrides:
        to­String in class Object
        Returns:
        a string representation of this operation for debugging purpose.