Package org.apache.sis.io.wkt

Class WKTDictionary

java.lang.Object
org.apache.sis.util.iso.AbstractFactory
org.apache.sis.referencing.factory.GeodeticAuthorityFactory
org.apache.sis.io.wkt.WKTDictionary
All Implemented Interfaces:
org.opengis.referencing.AuthorityFactory, org.opengis.util.Factory
public class WKTDictionary extends GeodeticAuthorityFactory
A factory providing CRS objects parsed from WKT definitions associated to authority codes. Each WKT definition is associated to a key according the authority:version:code pattern where code is mandatory and authority:version are optional. Coordinate Reference Systems or other kinds of objects are created from WKT definitions when a create(…) method is invoked for the first time for a given key.

Sub-classing and instantiation

Newly constructed WKTDictionary are initially empty. The dictionary can be populated in the following ways: Sub-classing may be necessary even if fetchDefinition(…) is not overridden because WKTDictionary does not implement any of the CRSAuthorityFactory, CSAuthorityFactory or DatumAuthorityFactory. The choice of interfaces to implement is left to subclasses.
Example: extend the set of Coordinate Reference Systems recognized by CRS.forCode(String). The additional CRS are defined by Well-Known Text strings in a "MyCRS.txt" file. First step is to create a CRS factory with those definitions: The second step is to register this factory as a service with a META-INF/services/org.opengis.referencing.crs.CRSAuthorityFactory file on the classpath. That file shall contain the fully qualified class name of above MyCRS class.

Errors management

Well-Known Text parsing is performed in two steps, each of them executed at a different time:

Early validation

WKT strings added by load(…) or addDefinitions(…) methods are verified for matching quotes, balanced parenthesis or brackets, and valid number or date formats. If a syntax error is detected, the loading process is interrupted at the point the error occurred; CRS definitions after the error location are not loaded. However, WKT keywords and geodetic parameters (e.g. map projections) are not validated at this stage.

Late validation

WKT keywords and geodetic parameters inside WKT elements are validated only when createObject(String) is invoked. If an error occurs at this stage, only the CRS (or other geodetic object) for the code given to the createFoo(…) method become invalid. Objects associated to other codes are not impacted.

Multi-threading

This class is thread-safe but not necessarily concurrent. This class is designed for a relatively small amount of WKT; it is not a replacement for database-backed factory such as EPSGFactory.
Since:
1.1
Version:
1.1
Author:
Martin Desruisseaux (Geomatys)

  • Field Details

    • parser

      protected final WKTFormat parser
      The parser to use for creating geodetic objects from WKT definitions. Subclasses can modify the WKTFormat configuration in their constructor, but should not use it directly after construction (for thread safety reasons).

  • Constructor Details

    • WKTDictionary

      public WKTDictionary(org.opengis.metadata.citation.Citation authority)
      Creates an initially empty factory. The authority can specified explicitly or inferred from the WKTs. In the latter case (when the given authority is null), an authority will be inferred from all ID[…] or AUTHORITY[…] elements found in WKT strings as below, in preference order:
      1. Most frequent CITATION[…] value.
      2. If there is no citation, then most frequent code space in ID[…] or AUTHORITY[…] elements.
      The WKT strings are specified by calls to load(BufferedReader) or addDefinitions(Stream) after construction.
      Parameters:
      authority - organization that defines the codes recognized by this factory, or null.

  • Method Details

    • load

      public void load(BufferedReader source) throws org.opengis.util.FactoryException
      Adds to this factory all definitions read from the given source. Each Coordinate Reference System (or other geodetic object) is defined by a string in WKT format. The key associated to each object is given by the ID[…] or AUTHORITY[…] element, which is typically the last element of a WKT string and is mandatory for definitions in this file.

      WKT strings can span many lines. All lines after the first line shall be indented with at least one white space. Non-indented lines start new definitions.

      Blank lines and lines starting with the # character (ignoring white spaces) are ignored.

      Aliases for WKT fragments

      Files with more than one WKT definition tend to repeat the same WKT fragments many times. For example, the same BaseGeogCRS[…] element may be repeated in every ProjectedCRS definitions. Redundant fragments can be replaced by aliases for making the file more compact, easier to read, faster to parse and with smaller memory footprint.

      Each line starting with "SET <identifier>=<WKT>" defines an alias for a fragment of WKT string. The WKT can span many lines as described above. Aliases are local to the file where they are defined. Aliases can be expanded in other WKT strings by "$<identifier>".

      Validation

      This method verifies that definitions have matching quotes, balanced parenthesis or brackets, and valid number or date formats. It does not verify WKT keywords or geodetic parameters. See class javadoc for more details.

      Example

      An example is available here.
      Parameters:
      source - the source of WKT definitions.
      Throws:
      org.opengis.util.FactoryException - if the definition file cannot be read.

    • addDefinitions

      public void addDefinitions(Stream<String> objects) throws org.opengis.util.FactoryException
      Adds definitions of CRS (or other geodetic objects) from Well-Known Texts. Blank strings are ignored. Each non-blank String shall contain the complete definition of exactly one geodetic object. A geodetic object cannot have its definition splitted in two or more Strings.

      The key associated to each object is given by the ID[…] or AUTHORITY[…] element, which is typically the last element of a WKT string and is mandatory. WKT strings can contain line separators for human readability.

      Parameters:
      objects - CRS (or other geodetic objects) definitions as WKT strings.
      Throws:
      org.opengis.util.FactoryException - if a WKT cannot be parsed, or does not contain an ID[…] or AUTHORITY[…] element, or if the same codespace:version:code tuple is used for two objects.

    • fetchDefinition

      protected String fetchDefinition(DefaultIdentifier identifier) throws org.opengis.util.FactoryException
      Fetches the Well-Known Text for a user-specified identifier not found in this WKTDictionary. Subclasses can override this method if WKT strings are not loaded or specified in advance, but instead fetched when first needed. An example of such scenario is WKTs provided by the "spatial_ref_sys" table of a spatial database. If no WKT is found for the given identifier, then this method returns null.

      On input, identifier contains only the pieces of information provided by user. For example if user invoked createGeographicCRS("Foo"), then the identifier code will be "Foo" but the codespace and version will be undefined (null). On output, identifier should be completed with missing code space and version (if available).

      Overriding

      The default implementation returns null. If a subclass overrides this method, then it should also override getAuthorityCodes(Class) because WKTDictionary does not know the codes that this method can recognize.
      Parameters:
      identifier - the code specified by user, possible with code space and version.
      Returns:
      Well-Known Text (WKT) for the given identifier, or null if none.
      Throws:
      org.opengis.util.FactoryException - if an error occurred while fetching the WKT.

    • getAuthority

      public org.opengis.metadata.citation.Citation getAuthority()
      Returns the authority or specification that defines the codes recognized by this factory. This is the first of the following values, in preference order:
      1. The authority explicitly specified at construction time.
      2. A citation built from the most frequent value found in CITATION elements.
      3. A citation built from the most frequent value found in ID or AUTHORITY elements.
      Specified by:
      getAuthority in interface org.opengis.referencing.AuthorityFactory
      Specified by:
      getAuthority in class GeodeticAuthorityFactory
      Returns:
      the organization responsible for CRS definitions, or null if unknown.
      See Also:

    • getCodeSpaces

      public Set<String> getCodeSpaces()
      Returns all namespaces recognized by this factory. Those namespaces can appear before codes in calls to createFoo(String) methods, for example "ESRI" in "ESRI:102018". Namespaces are case-insensitive.
      Overrides:
      getCodeSpaces in class GeodeticAuthorityFactory
      Returns:
      the namespaces recognized by this factory.

    • getAuthorityCodes

      public Set<String> getAuthorityCodes(Class<? extends org.opengis.referencing.IdentifiedObject> type) throws org.opengis.util.FactoryException
      Returns the set of authority codes for objects of the given type. The type argument specifies the base type of identified objects.
      Parameters:
      type - the spatial reference objects type.
      Returns:
      the set of authority codes for spatial reference objects of the given type.
      Throws:
      org.opengis.util.FactoryException - if an error occurred while fetching the codes.

    • getDescriptionText

      public org.opengis.util.InternationalString getDescriptionText(String code) throws org.opengis.util.FactoryException
      Gets a description of the object corresponding to a code.
      Specified by:
      getDescriptionText in interface org.opengis.referencing.AuthorityFactory
      Overrides:
      getDescriptionText in class GeodeticAuthorityFactory
      Parameters:
      code - value allocated by authority.
      Returns:
      a description of the object, or null if null if none.
      Throws:
      org.opengis.referencing.NoSuchAuthorityCodeException - if the specified code was not found.
      org.opengis.util.FactoryException - if the query failed for some other reason.

    • createObject

      public org.opengis.referencing.IdentifiedObject createObject(String code) throws org.opengis.util.FactoryException
      Returns an arbitrary object from a code.
      Specified by:
      createObject in interface org.opengis.referencing.AuthorityFactory
      Specified by:
      createObject in class GeodeticAuthorityFactory
      Parameters:
      code - value allocated by authority.
      Returns:
      the object for the given code.
      Throws:
      org.opengis.referencing.NoSuchAuthorityCodeException - if the specified code was not found.
      org.opengis.util.FactoryException - if the object creation failed for some other reason.
      See Also: