Module org.apache.sis.feature
Package org.apache.sis.feature

Class AbstractFeature

Object
AbstractFeature
All Implemented Interfaces:
Serializable
public abstract class AbstractFeature extends Object implements Serializable
An instance of a feature type containing values for a real-world phenomena. Each feature instance can provide values for the following properties: Abstract­Feature can be instantiated by calls to Default­Feature­Type​.new­Instance().

Simple features

A feature is said “simple” if it complies to the following conditions:
  • the feature allows only attributes and operations (no associations),
  • the cardinality of all attributes is constrained to [1 … 1].

Operations

Properties that are instances of Operation are usually not stored in Feature instances. Instead, the Operation​.apply(…) method is invoked every times that the property value is requested. Abstract­Feature does not cache operation results. Those results are usually read-only, but may be writable under the conditions documented in set­Operation­Value(String, Object).

Limitations

  • Multi-threading: Abstract­Feature instances are not thread-safe. Synchronization, if needed, shall be done externally by the caller.
  • Serialization: serialized objects of this class are not guaranteed to be compatible with future versions. Serialization should be used only for short term storage or RMI between applications running the same SIS version.
Since:
0.5
See Also:

  • Constructor Details

  • Method Details

    • getType

      public DefaultFeatureType getType()
      Returns information about the feature (name, characteristics, etc.).
      Warning: In a future SIS version, the return type may be changed to org​.opengis​.feature​.Feature­Type. This change is pending GeoAPI revision.
      Returns:
      information about the feature.

    • getProperty

      public Object getProperty(String name) throws IllegalArgumentException
      Returns the property (attribute, feature association or operation result) of the given name. If the property type is a parameterless operation, then this method may return the result of executing the operation on this feature, at implementation choice.

      This method returns the property instance. If only the property value is desired, then get­Property­Value(String) is preferred since it gives to SIS a chance to avoid the creation of Abstract­Attribute or Abstract­Association instances.

      Note for subclass implementers

      The default implementation returns an instance that redirect all read and write operations to get­Property­Value(String) and set­Property­Value(String, Object) respectively. That default implementation is intended to make easier for developers to create their own customized Abstract­Facture implementations, but has drawbacks: a new Property instance is created every time that this get­Property(String) method is invoked, and the returned Property implementation is not very efficient since it has to perform multiple lookups and type checks. Implementers are encouraged to override this method if they can provide a more efficient implementation. Note that this is already the case when using implementations created by Default­Feature­Type​.new­Instance().
      Warning: In a future SIS version, the return type may be changed to org​.opengis​.feature​.Property. This change is pending GeoAPI revision.
      Parameters:
      name - the property name.
      Returns:
      the property of the given name (never null).
      Throws:
      Illegal­Argument­Exception - if the given argument is not a property name of this feature.
      See Also:

    • setProperty

      public void setProperty(Object property) throws IllegalArgumentException
      Sets the property (attribute or feature association). The given property shall comply to the following conditions:
      • It must be non-null.
      • Its name shall be the name of the property to set in this feature.
      • Its type shall be the same instance than the property type defined by the feature type for the above name. In other words, the following condition shall hold:
      assert property.getType() == getType().getProperty(property.getName());
      This method is useful for storing non-default Attribute or Feature­Association implementations in this feature. When default implementations are sufficient, the set­Property­Value(String, Object) method is preferred.

      Note for subclass implementers

      The default implementation verifies that the given property has the expected type and a null or empty map of characteristics, then delegates to set­Property­Value(String, Object). That default implementation is intended to make easier for developers to create their own customized Abstract­Facture implementations, but has drawbacks: the given Property instance is not stored (only its value is stored), and it cannot have custom characteristics. Implementers are encouraged to override this method if they can provide a better implementation. Note that this is already the case when using implementations created by Default­Feature­Type​.new­Instance().
      Warning: In a future SIS version, the argument may be changed to org​.opengis​.feature​.Property. This change is pending GeoAPI revision.
      Parameters:
      property - the property to set.
      Throws:
      Illegal­Argument­Exception - if the name of the given property is not a property name of this feature.
      Illegal­Argument­Exception - if the value of the given property is not valid.
      Illegal­Argument­Exception - if the property cannot be set for another reason.
      See Also:

    • getPropertyValue

      public abstract Object getPropertyValue(String name) throws IllegalArgumentException
      Returns the value for the property of the given name. This convenience method is equivalent to invoking get­Property(String) for the given name, then to perform one of the following actions depending on the property type and the multiplicity:
      Class of returned value
      Property type max. occurs Method invoked Return type
      AttributeType 0 or 1 Attribute.getValue() Object
      AttributeType 2 or more Attribute.getValues() Collection<?>
      FeatureAssociationRole 0 or 1 FeatureAssociation.getValue() Feature
      FeatureAssociationRole 2 or more FeatureAssociation.getValues() Collection<Feature>
      Note: “max. occurs” is the maximum number of occurrences and does not depend on the actual number of values. If an attribute allows more than one value, then this method will always return a collection for that attribute even if the collection is empty.

      Multi-valued properties and collections

      In the case of multi-valued properties (“max. occurs” > 1), the collection returned by this method may or may not be modifiable, at implementation choice. Generally the caller cannot add new elements into the returned collection anyway since Collection<?> does not allow such operations, and more specific casts (e.g. Collection<String> cannot be checked at runtime. If a type-safe modifiable collection is desired, the following approach can be used instead: 
      Attribute<String> attribute = Features.cast((Attribute<?>) feature.getProperty(name), String.class);
Collection<String> values = attribute.getValues();    // This collection is guaranteed to be "live".
      Parameters:
      name - the property name.
      Returns:
      value of the specified property, or the default value (which may be null} if none.
      Throws:
      Illegal­Argument­Exception - if the given argument is not an attribute or association name of this feature.
      See Also:

    • setPropertyValue

      public abstract void setPropertyValue(String name, Object value) throws IllegalArgumentException
      Sets the value for the property of the given name.

      Validation

      The amount of validation performed by this method is implementation dependent. Usually, only the most basic constraints are verified. This is so for performance reasons and also because some rules may be temporarily broken while constructing a feature. A more exhaustive verification can be performed by invoking the quality() method.
      Parameters:
      name - the attribute name.
      value - the new value for the given attribute (may be null).
      Throws:
      Illegal­Argument­Exception - if the given name is not an attribute or association name of this feature.
      Class­Cast­Exception - if the value is not assignable to the expected value class.
      Illegal­Argument­Exception - if the given value is not valid for a reason other than its type.
      See Also:

    • getValueOrFallback

      public abstract Object getValueOrFallback(String name, Object missingPropertyFallback)
      Returns the value for the property of the given name if that property exists, or a fallback value otherwise. This method is equivalent to the following code, but potentially more efficient when the property does not exist: 
      try {
    return getPropertyValue(name);
} catch (PropertyNotFoundException ignore) {
    return missingPropertyFallback
}
      Note that if a property of the given name exists but has no value, then this method returns the default value (which may be null). Property without value is not equivalent to non-existent property.
      Parameters:
      name - the property name.
      missing­Property­Fallback - the (potentially null) value to return if no attribute or association of the given name exists.
      Returns:
      value or default value of the specified property, or missing­Property­Fallback if no attribute or association of that name exists. This value may be null.
      Since:
      1.1

    • getOperationValue

      protected Object getOperationValue(String name)
      Executes the parameterless operation of the given name and returns the value of its result. This is a convenience method for sub-classes where some properties may be operations that depend on other properties of this Feature instance (for example a link to another property value). Invoking this method is equivalent to performing the following steps: 
          public Object getPropertyValue(String name) {
        Operation operation = (Operation) type.getProperty(name);
        Property result = operation.apply(this, null);
        if (result instanceof Attribute<?>) {
            return ...;                                      // the attribute value.
        } else if (result instanceof FeatureAssociation) {
            return ...;                                      // the associated feature.
        } else {
            return null;
        }
    }
      Parameters:
      name - the name of the operation to execute. The caller is responsible to ensure that the property type for that name is an instance of Abstract­Operation.
      Returns:
      the result value of the given operation, or null if none.
      Since:
      0.8

    • setOperationValue

      protected void setOperationValue(String name, Object value)
      Executes the parameterless operation of the given name and sets the value of its result. This method is the complement of get­Operation­Value(String) for subclasses where some properties may be operations. Not all operations accept assignments, but the link and compound operations (for instances) do. Whether an operation is writable or not depends on whether the computed Property supports Abstract­Attribute​.set­Value(Object) or Abstract­Association​.set­Value(Feature).
      Parameters:
      name - the name of the operation to execute. The caller is responsible to ensure that the property type for that name is an instance of Abstract­Operation.
      value - the value to assign to the result of the named operation.
      Throws:
      Illegal­State­Exception - if the operation of the given name does not accept assignment.
      Since:
      0.8

    • quality

      public DataQuality quality()
      Evaluates the quality of this feature at this method invocation time. The data quality reports may include information about whether the property values met the constraints defined by the property types, or any other criterion at implementation choice.

      The default implementation reports data quality with at least the following information:

      This feature is valid if this method does not report any conformance result having a pass value of false.

      Example

      Given a feature with an attribute named “population”. If this attribute is mandatory ([1 … 1] multiplicity) but no value has been assigned to it, then this quality() method will return the following data quality report: 
         Data quality
     ├─Scope
     │   └─Level………………………………………………… Feature
     └─Report
         ├─Measure identification
         │   └─Code………………………………………… population
         ├─Evaluation method type…… Direct internal
         └─Result
             ├─Explanation……………………… Missing value for “population” property.
             └─Pass………………………………………… false
      Returns:
      reports on all constraint violations found.
      See Also:

    • toString

      public String toString()
      Formats this feature in a tabular format.
      Overrides:
      to­String in class Object
      Returns:
      a string representation of this feature in a tabular format.
      See Also:

    • hashCode

      public int hashCode()
      Returns a hash code value for this feature. The default implementation performs the following algorithm:
      • Iterate over all properties returned by type​.get­Property(true) – thus including properties inherited from parent types (if any):
        • For each property type, get the value with get­Property­Value(String).
        • Compute the hash code from the property name and value, ignoring the properties having a null value.
      Subclasses should override this method with a more efficient algorithm for their internal structure. There is no need to reproduce the same hash code value than the one computed by this default method.
      Overrides:
      hash­Code in class Object
      Returns:
      a hash code value.
      Since:
      0.8

    • equals

      public boolean equals(Object obj)
      Compares this feature with the given object for equality. The default implementation performs the following algorithm:
      • Verify that both objects are non-null and of the same class.
      • Iterate over all properties returned by type​.get­Property(true) – thus including properties inherited from parent types (if any):
      Subclasses should override this method with a more efficient algorithm for their internal structure.
      Overrides:
      equals in class Object
      Returns:
      true if both objects are equal.
      Since:
      0.8