Class OptionKey<T>

Type Parameters:
T - the type of option values.
All Implemented Interfaces:
Direct Known Subclasses:

public class OptionKey<T> extends Object implements Serializable
Keys in a map of options for configuring various services (Data­Store, etc). Option­Keys are used for aspects that usually do not need to be configured, except in a few specialized cases. For example most data file formats read by SIS do not require the user to specify the character encoding, since the encoding it is often given in the file header or in the format specification. However if SIS needs to read plain text files and the default platform encoding is not suitable, then the user can specify the desired encoding explicitly using the ENCODING option.

All options are hints and may be silently ignored. For example most Data­Stores will ignore the ENCODING option if irrelevant to their format, or if the encoding is specified in the data file header.

Options are transitive: if a service uses others services for its internal working, the given options may also be given to those dependencies, at implementation choice.

Defining new options

Developers who wish to define their own options can define static constants in a subclass, as in the following example:
public final class MyOptionKey<T> extends OptionKey<T> {
    public static final OptionKey<String> MY_OPTION = new MyOptionKey<>("MY_OPTION", String.class);

    private MyOptionKey(final String name, final Class<T> type) {
        super(name, type);
See Also:

Defined in the sis-utility module

  • Field Details

    • LOCALE

      public static final OptionKey<Locale> LOCALE
      The locale to use for locale-sensitive data. This option determines the language to use for writing international strings when the target storage support only one language. It may also control number and date patterns in some file formats like Comma Separated Values (CSV). However most data formats will ignore this locale.

      This option is not for the locale of logging or warning messages. Messages locale is rather controlled by Data­Store​.set­Locale(Locale).

      See Also:

      public static final OptionKey<TimeZone> TIMEZONE
      The timezone to use when parsing or formatting dates and times without explicit timezone. If this option is not provided, then the default value is format specific. That default is often, but not necessarily, the platform default.
      Upcoming API change — Java time API: the type may be changed to Zone­Id when Apache SIS will target Java 8. This change may be applied in synchronization with GeoAPI 4.0.
      See Also:

      public static final OptionKey<Charset> ENCODING
      The character encoding of document content. This option can be used when the file to read does not describe itself its encoding. For example this option can be used when reading plain text files, but is ignored when reading XML files having a <?xml version="1.0" encoding="…"?> declaration.

      If this option is not provided, then the default value is format specific. That default is often, but not necessarily, the platform default.

      See Also:

      public static final OptionKey<String> URL_ENCODING
      The encoding of a URL (not the encoding of the document content). This option may be used when converting a String or a URL to a URI or a File. The following rules apply:
      • URI are always encoded in UTF-8. Consequently this option is ignored for URI.
      • URL are often encoded in UTF-8, but not necessarily. Other encodings are possible (while not recommended), or some URL may not be encoded at all.
      If this option is not provided, then the URL is assumed not encoded.

      Example: Given the "file:Map%20with%20spaces​.png" URL, then:

      • If the URL encoding option is set to "UTF-8" or "ISO-8859-1", then:
        • the encoded URI will be "file:Map%20with%20spaces​.png";
        • the decoded URI or the file will be "file:Map with spaces​.png".
      • If the URL encoding option is set to null or is not provided, then:
        • the encoded URI will be "file:Map%2520with%2520spaces​.png", i.e. the percent sign will be encoded as "%25";
        • the decoded URI or the file will be "file:Map%20with%20spaces​.png".
      This option has not effect on URI encoding, which is always UTF-8.
      See Also:

      public static final OptionKey<OpenOption[]> OPEN_OPTIONS
      Whether a storage object (e.g. a Data­Store) shall be opened in read, write, append or other modes. The main options that can be provided are:
      Supported open options
      Value Meaning
      StandardOpenOption.READ Open for reading data from the storage object.
      StandardOpenOption.WRITE Open for modifying existing data in the storage object.
      StandardOpenOption.APPEND Open for appending new data in the storage object.
      StandardOpenOption.CREATE Creates a new storage object (file or database) if it does not exist.

      public static final OptionKey<ByteBuffer> BYTE_BUFFER
      The byte buffer to use for input/output operations. Some Data­Store implementations allow a byte buffer to be specified, thus allowing users to choose the buffer capacity, whether the buffer is direct, or to recycle existing buffers.

      It is user's responsibility to ensure that:

      • The buffer does not contains any valuable data, as it will be cleared.
      • The same buffer is not used concurrently by two different Data­Store instances.

      public static final OptionKey<GeometryLibrary> GEOMETRY_LIBRARY
      The library to use for creating geometric objects at reading time. Some libraries are the Java Topology Suite (JTS), ESRI geometry API and Java2D. If this option is not specified, then a default library will be selected among the libraries available in the runtime environment.

      public static final OptionKey<Integer> INDENTATION
      The number of spaces to use for indentation when formatting text files in WKT or XML formats. A value of -1 means to format the whole WKT or XML document on a single line without line feeds or indentation.

      If this option is not provided, then the most typical default value used in Apache SIS is 2. Such small indentation value is used because XML documents defined by OGC standards tend to be verbose.

      See Also:
  • Constructor Details

    • OptionKey

      protected OptionKey(String name, Class<T> type)
      Creates a new key of the given name for values of the given type.
      name - the key name.
      type - the type of values.
  • Method Details

    • getName

      public String getName()
      Returns the name of this option key.
      the name of this option key.
    • getElementType

      public final Class<T> getElementType()
      Returns the type of values associated to this option key.
      the type of values.
    • getValueFrom

      public T getValueFrom(Map<OptionKey<?>,?> options)
      Returns the option value in the given map for this key, or null if none. This is a convenience method for implementers, which can be used as below:
      public <T> T getOption(final OptionKey<T> key) {
          ArgumentChecks.ensureNonNull("key", key);
          return key.getValueFrom(options);
      options - the map where to search for the value, or null if not yet created.
      the current value in the map for the this option, or null if none.
    • setValueInto

      public Map<OptionKey<?>,Object> setValueInto(Map<OptionKey<?>,Object> options, T value)
      Sets a value for this option key in the given map, or in a new map if the given map is null. This is a convenience method for implementers, which can be used as below:
      public <T> void setOption(final OptionKey<T> key, final T value) {
          ArgumentChecks.ensureNonNull("key", key);
          options = key.setValueInto(options, value);
      options - the map where to set the value, or null if not yet created.
      value - the new value for the given option, or null for removing the value.
      the given map of options, or a new map if the given map was null. The returned value may be null if the given map and the given value are both null.
    • equals

      public boolean equals(Object object)
      Returns true if the given object is an instance of the same class having the same name and type.
      equals in class Object
      object - the object to compare with this Option­Key for equality.
    • hashCode

      public int hashCode()
      Returns a hash code value for this object.
      hash­Code in class Object
    • toString

      public String toString()
      Returns a string representation of this option key. The default implementation returns the value of get­Name().
      to­String in class Object