org.apache.sis.referencing

## Class IdentifiedObjects

- Object
- - Static
  - - IdentifiedObjects

-     public final class IdentifiedObjects
      extends Static

  Utility methods working on arbitrary implementations of the `IdentifiedObject` interface.
  Since:
    0.4
  See Also:
    `CRS`, `Envelopes`

  Defined in the `sis-referencing` module

- - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Identifier` | `getIdentifier(IdentifiedObject object, Citation authority)` Returns an identifier for the given object according the given authority.
    `static String` | `getIdentifierOrName(IdentifiedObject object)` Returns the string representation of the first identifier, or the object name if there is no identifier.
    `static String` | `getName(IdentifiedObject object, Citation authority)` Returns an object name according the given authority.
    `static Set<String>` | `getNames(IdentifiedObject object, Citation authority)` Returns every object names and aliases according the given authority.
    `static Map<String,?>` | `getProperties(IdentifiedObject object, String... excludes)` Returns the information provided in the specified identified object as a map of properties.
    `static String` | `getUnicodeIdentifier(IdentifiedObject object)` Returns the first name, alias or identifier which is a valid Unicode identifier.
    `static boolean` | `isHeuristicMatchForName(IdentifiedObject object, String name)` Returns `true` if either the primary name or at least one alias matches the given string according heuristic rules.
    `static Integer` | `lookupEPSG(IdentifiedObject object)` Looks up an EPSG code, such as `4326`, of the specified object.
    `static String` | `lookupURN(IdentifiedObject object, Citation authority)` Looks up a URN, such as `"urn:ogc:def:crs:EPSG:9.1:4326"`, of the specified object.
    `static IdentifiedObjectFinder` | `newFinder(String authority)` Creates a finder which can be used for looking up unidentified objects.
    `static String` | `toString(Identifier identifier)` Returns a string representation of the given identifier.
    `static String` | `toURN(Class<?> type, Identifier identifier)` Returns the URN of the given identifier, or `null` if no valid URN can be formed.

    - ### Methods inherited from class Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### getProperties

          public static Map<String,?> getProperties(IdentifiedObject object,
                                                    String... excludes)

      Returns the information provided in the specified identified object as a map of properties. The returned map contains the following entries for each key not contained in the `excludes` list and for which the corresponding method returns a non-null and non-empty value.

      Provided properties
      Key | Value
      --- | ---
      "name" | `IdentifiedObject.getName()`
      "alias" | `IdentifiedObject.getAlias()`
      "identifiers" | `IdentifiedObject.getIdentifiers()`
      "remarks" | `IdentifiedObject.getRemarks()`
      "scope" | `CoordinateOperation.getScope()` (also in datum and reference systems)
      "domainOfValidity" | `CoordinateOperation.getDomainOfValidity()` (also in datum and reference systems)
      "operationVersion" | `CoordinateOperation.getOperationVersion()`
      "coordinateOperationAccuracy" | `CoordinateOperation.getCoordinateOperationAccuracy()`
      "formula" | `OperationMethod.getFormula()`
      "deprecated" | `AbstractIdentifiedObject.isDeprecated()`

      Note: the current implementation does not provide "minimumValue", "maximumValue" or "rangeMeaning" entry for `CoordinateSystemAxis` instances because the minimum and maximum values depend on the units of measurement.
      Parameters:
        `object` - the identified object to view as a properties map.
        `excludes` - the keys of properties to exclude from the map.
      Returns:
        a view of the identified object properties as an immutable map.

    - #### getNames

          public static Set<String> getNames(IdentifiedObject object,
                                             Citation authority)

      Returns every object names and aliases according the given authority. This method performs the same work than `getName(IdentifiedObject, Citation)`, except that it does not stop at the first match. This method is useful in the rare cases where the same authority declares more than one name, and all those names are of interest.
      Parameters:
        `object` - the object to get the names and aliases from, or `null`.
        `authority` - the authority for the names to return, or `null` for any authority.
      Returns:
        the object's names and aliases, or an empty set if no name or alias matching the specified authority has been found.

    - #### getName

          public static String getName(IdentifiedObject object,
                                       Citation authority)

      Returns an object name according the given authority. This method checks first the primary name, then all aliases in their iteration order.
      - If the name or alias implements the `Identifier` interface, then this method compares the identifier authority against the specified citation using the `Citations​.identifierMatches(Citation, Citation)` method. If a matching is found, then this method returns the identifier code of that object.
      - Otherwise, if the alias implements the `GenericName` interface, then this method compares the name scope against the specified citation using the `Citations​.identifierMatches(Citation, String)` method. If a matching is found, then this method returns the name tip of that object.
      Note that alias may implement both the `Identifier` and `GenericName` interfaces (for example `NamedIdentifier`). In such cases, the identifier view has precedence.
      Parameters:
        `object` - the object to get the name from, or `null`.
        `authority` - the authority for the name to return, or `null` for any authority.
      Returns:
        the object's name (either an identifier code or a name tip), or `null` if no name matching the specified authority has been found.
      See Also:
        `AbstractIdentifiedObject​.getName()`

    - #### getIdentifier

          public static Identifier getIdentifier(IdentifiedObject object,
                                                 Citation authority)

      Returns an identifier for the given object according the given authority. This method checks all identifiers in their iteration order and returns the first identifier with an authority citation matching the specified authority.
      Parameters:
        `object` - the object to get the identifier from, or `null`.
        `authority` - the authority for the identifier to return, or `null` for the first identifier regardless its authority.
      Returns:
        the object's identifier, or `null` if no identifier matching the specified authority has been found.
      See Also:
        `AbstractIdentifiedObject​.getIdentifier()`

    - #### getIdentifierOrName

          public static String getIdentifierOrName(IdentifiedObject object)

      Returns the string representation of the first identifier, or the object name if there is no identifier. This method searches for the first non-null element in `object.getIdentifiers()`. If there is none, then this method fallback on `object.getName()`. The first element found is formatted by `toString(Identifier)`.
      Recommended alternatives
      - If the code of a specific authority is wanted (typically EPSG), then consider using `getIdentifier(IdentifiedObject, Citation)` instead.
      - In many cases, the identifier is not specified. For an exhaustive scan of the EPSG database looking for a match, use one of the search methods defined below.
      Parameters:
        `object` - the identified object, or `null`.
      Returns:
        a string representation of the first identifier or name, or `null` if none.
      See Also:
        `getIdentifier(IdentifiedObject, Citation)`, `lookupURN(IdentifiedObject, Citation)`

    - #### getUnicodeIdentifier

          public static String getUnicodeIdentifier(IdentifiedObject object)

      Returns the first name, alias or identifier which is a valid Unicode identifier. This method performs the search in the following order:
      - `object.getName()`
      - `object.getAlias()` in iteration order
      - `object.getIdentifiers()` in iteration order
      Parameters:
        `object` - the identified object, or `null`.
      Returns:
        the first name, alias or identifier which is a valid Unicode identifier, or `null` if none.
      See Also:
        `ImmutableIdentifier`, `Citations​.getUnicodeIdentifier(Citation)`, `CharSequences​.isUnicodeIdentifier(CharSequence)`

    - #### lookupURN

          public static String lookupURN(IdentifiedObject object,
                                         Citation authority)
                                  throws FactoryException

      Looks up a URN, such as `"urn:ogc:def:crs:EPSG:9.1:4326"`, of the specified object. This method searches in all geodetic authority factories known to SIS for an object approximatively equals to the specified object. Then there is a choice:
      - If a single matching object is found in the specified authority factory, then its URN is returned.
      - Otherwise if the given object is a `CompoundCRS` or `ConcatenatedOperation` and all components have an URN, then this method returns a combined URN.
      - Otherwise this method returns `null`.

      Note that this method checks the identifier validity. If the given object declares explicitly an identifier, then this method will instantiate an object from the authority factory using that identifier and compare it with the given object. If the comparison fails, then this method returns `null`. Consequently this method may return `null` even if the given object declares explicitly its identifier. If the declared identifier is wanted unconditionally, one can use the following pattern instead:

          String urn = toURN(object.getClass(), getIdentifier(object, authority));

      This method can be seen as a converse of `CRS​.forCode(String)`.
      Parameters:
        `object` - the object (usually a coordinate reference system) whose identifier is to be found, or `null`.
        `authority` - the authority for the identifier to return, or `null` for the first identifier regardless its authority.
      Returns:
        the identifier, or `null` if none was found without ambiguity or if the given object was null.
      Throws:
        `FactoryException` - if an error occurred during the search.
      Since:
        0.7
      See Also:
        `newFinder(String)`, `toURN(Class, Identifier)`

    - #### lookupEPSG

          public static Integer lookupEPSG(IdentifiedObject object)
                                    throws FactoryException

      Looks up an EPSG code, such as `4326`, of the specified object. This method searches in EPSG factories known to SIS for an object approximatively equals to the specified object. If such an object is found, then its EPSG identifier is returned. Otherwise or if there is ambiguity, this method returns `null`.

      Note that this method checks the identifier validity. If the given object declares explicitly an identifier, then this method will instantiate an object from the EPSG factory using that identifier and compare it with the given object. If the comparison fails, then this method returns `null`. Consequently this method may return `null` even if the given object declares explicitly its identifier. If the declared identifier is wanted unconditionally, one can use the following pattern instead:

          String code = toString(getIdentifier(object, Citations.EPSG));

      This method can be seen as a converse of `CRS​.forCode(String)`.
      Parameters:
        `object` - the object (usually a coordinate reference system) whose EPSG code is to be found, or `null`.
      Returns:
        the EPSG code, or `null` if none was found without ambiguity or if the given object was null.
      Throws:
        `FactoryException` - if an error occurred during the search.
      Since:
        0.7
      See Also:
        `newFinder(String)`

    - #### newFinder

          public static IdentifiedObjectFinder newFinder(String authority)
                                                  throws NoSuchAuthorityFactoryException,
                                                         FactoryException

      Creates a finder which can be used for looking up unidentified objects. This method is an alternative to `lookup(…)` methods when more control are desired.
      Example 1: be lenient regarding axis order
      By default, `lookup(…)` methods require that objects in the dataset have their axes in the same order than the given object. For relaxing this condition, one can use the following Java code. This example assumes that at most one object from the dataset will match the given object. If more than one object may match, then the call to `findSingleton(…)` should be replaced by `find(…)`.

          IdentifiedObjectFinder finder = IdentifiedObjects.newFinder(null);
          finder.setIgnoringAxes(true);
          IdentifiedObject found = finder.findSingleton(object);

      Example 2: extend the search to deprecated definitions
      By default, `lookup(…)` methods exclude deprecated objects from the search. To search also among deprecated objects, one can use the following Java code: This example does not use the `findSingleton(…)` convenience method on the assumption that the search may find both deprecated and non-deprecated objects.

          IdentifiedObjectFinder finder = IdentifiedObjects.newFinder(null);
          finder.setSearchDomain(IdentifiedObjectFinder.Domain.ALL_DATASET);
          Set<IdentifiedObject> found = finder.find(object);

      Parameters:
        `authority` - the authority of the objects to search (typically `"EPSG"` or `"OGC"`), or `null` for searching among the objects created by all authorities.
      Returns:
        a finder to use for looking up unidentified objects.
      Throws:
        `NoSuchAuthorityFactoryException` - if the given authority is not found.
        `FactoryException` - if the finder can not be created for another reason.
      See Also:
        `lookupEPSG(IdentifiedObject)`, `lookupURN(IdentifiedObject, Citation)`, `GeodeticAuthorityFactory​.newIdentifiedObjectFinder()`, `IdentifiedObjectFinder​.find(IdentifiedObject)`

    - #### isHeuristicMatchForName

          public static boolean isHeuristicMatchForName(IdentifiedObject object,
                                                        String name)

      Returns `true` if either the primary name or at least one alias matches the given string according heuristic rules. If the given object is an instance of `AbstractIdentifiedObject`, then this method delegates to its `isHeuristicMatchForName(String)` method in order to leverage the additional rules implemented by sub-classes. Otherwise the fallback implementation returns `true` if the given `name` is equal, ignoring aspects documented below, to one of the following names:
      - The primary name's code (without codespace).
      - Any alias's tip (without scope and namespace).
      The comparison ignores the following aspects:
      - Lower/upper cases.
      - Some Latin diacritical signs (e.g. `"Réunion"` and `"Reunion"` are considered equal).
      - All characters that are not letters or digits (e.g. `"Mercator (1SP)"` and `"Mercator_1SP"` are considered equal).
      - Namespaces or scopes, because this method is typically invoked with either the value of an other `IdentifiedObject​.getName()​.getCode()` or with the Well Known Text (WKT) projection or parameter name.
      If the `object` argument is `null`, then this method returns `false`.
      Parameters:
        `object` - the object for which to check the name or alias, or `null`.
        `name` - the name to compare with the object name or aliases.
      Returns:
        `true` if the primary name or at least one alias matches the specified `name`.
      See Also:
        `AbstractIdentifiedObject​.isHeuristicMatchForName(String)`

    - #### toURN

          public static String toURN(Class<?> type,
                                     Identifier identifier)

      Returns the URN of the given identifier, or `null` if no valid URN can be formed. This method builds a URN from the codespace, version and code of the given identifier, completed by the given `Class` argument.

      First, this method starts the URN with `"urn:"` followed by a namespace determined from the identifier codespace (which is usually an abbreviation of the identifier authority). The recognized namespaces are listed in the following table (note that the list of authorities than can be used in the `"urn:ogc:def"` namespace is specified by the OGC Naming Authority). If this method can not determine a namespace for the given identifier, it returns `null`.

      Valid values for the authority component in URN
      Namespace | Authority in URN | Description
      --- | --- | ---
      `urn:ogc:def` | `EPSG` | EPSG dataset
      `urn:ogc:def` | `OGC` | Open Geospatial Consortium
      `urn:ogc:def` | `OGC-WFS` | OGC Web Feature Service
      `urn:ogc:def` | `SI` | Système International d'Unités
      `urn:ogc:def` | `UCUM` | Unified Code for Units of Measure
      `urn:ogc:def` | `UNSD` | United Nations Statistics Division
      `urn:ogc:def` | `USNO` | United States Naval Observatory

      The namespace is followed by the authority, then by a type determined from the given `Class` argument. That class is usually determined simply by `IdentifiedObject​.getClass()`. The given class shall be assignable to one of the following types, otherwise this method returns `null`:

      Valid values for the type component in URN
      Interface | Type in URN | Description
      --- | --- | ---
      `CoordinateSystemAxis` | `axis` | Coordinate system axe definition
      `CoordinateOperation` | `coordinateOperation` | Coordinate operation definition
      `CoordinateReferenceSystem` | `crs` | Coordinate reference system definition
      `CoordinateSystem` | `cs` | Coordinate system definition
      `Datum` | `datum` | Datum definition
      `Ellipsoid` | `ellipsoid` | Ellipsoid definition
      `PrimeMeridian` | `meridian` | Prime meridian definition
      `OperationMethod` | `method` | Operation method definition
      `ParameterDescriptor` | `parameter` | Operation parameter definition
      `ReferenceSystem` | `referenceSystem` | Value reference system definition
      `Unit` | `uom` | Unit of measure definition

      The type is followed by the codespace version if available, and finally by the code value.

      The above tables may be expanded in any future SIS version.

      Parameters:
        `type` - a type assignable to one of the types listed in above table.
        `identifier` - the identifier for which to format a URN, or `null`.
      Returns:
        the URN for the given identifier, or `null` if the given identifier was null or can not be formatted by this method.
      Since:
        0.7
      See Also:
        `lookupURN(IdentifiedObject, Citation)`

    - #### toString

          public static String toString(Identifier identifier)

      Returns a string representation of the given identifier. This method applies the following rules:
      - If the given identifier implements the `GenericName` interface, then this method delegates to the `GenericName​.toString()` method.
      - Otherwise if the given identifier has a code space, then formats the identifier as "`codespace:code`".
      - Otherwise if the given identifier has an authority, then formats the identifier as "`authority:code`".
      - Otherwise returns the identifier code.
      This method is provided because the `GenericName​.toString()` behavior is specified by its javadoc, while `Identifier` has no such contract. For example like most ISO 19115 objects in SIS, the `DefaultIdentifier` implementation is formatted as a tree. This static method can be used when a "name-like" representation is needed for any implementation.
      Parameters:
        `identifier` - the identifier, or `null`.
      Returns:
        a string representation of the given identifier, or `null`.
      See Also:
        `FormattableObject​.toString()`, `NamedIdentifier​.toString()`

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