Constructor Detail

• StrLookup

  protected StrLookup()

  Constructor.

Method Detail

• noneLookup

  public static StrLookup<?> noneLookup()

  Returns a lookup which always returns null.

  Returns:

  a lookup that always returns null, not null

• systemPropertiesLookup

  public static StrLookup<String> systemPropertiesLookup()

  Returns a lookup which uses System properties to lookup the key to value.

  If a security manager blocked access to system properties, then null will be returned from every lookup.

  If a null key is used, this lookup will throw a NullPointerException.

  Returns:

  a lookup using system properties, not null

• mapLookup

  public static <V> StrLookup<V> mapLookup(Map<String,V> map)

  Returns a lookup which looks up values using a map.

  If the map is null, then null will be returned from every lookup. The map result object is converted to a string using toString().

  Type Parameters:

  V - the type of the values supported by the lookup

  Parameters:

  map - the map of keys to values, may be null

  Returns:

  a lookup using the map, not null

• lookup

  public abstract String lookup(String key)

  Looks up a String key to a String value.

  The internal implementation may use any mechanism to return the value. The simplest implementation is to use a Map. However, virtually any implementation is possible.

  For example, it would be possible to implement a lookup that used the key as a primary key, and looked up the value on demand from the database Or, a numeric based implementation could be created that treats the key as an integer, increments the value and return the result as a string - converting 1 to 2, 15 to 16 etc.

  The lookup(String) method always returns a String, regardless of the underlying data, by converting it as necessary. For example:

   Map map = new HashMap();
   map.put("number", Integer.valueOf(2));
   assertEquals("2", StrLookup.mapLookup(map).lookup("number"));
   

  Parameters:

  key - the key to be looked up, may be null

  Returns:

  the matching value, null if no match