Package org.apache.commons.configuration2

Interface Configuration

All Superinterfaces:
ImmutableConfiguration, SynchronizerSupport
All Known Subinterfaces:
FileBasedConfiguration, HierarchicalConfiguration<T>
All Known Implementing Classes:
AbstractConfiguration, AbstractHierarchicalConfiguration, AbstractYAMLBasedConfiguration, AppletConfiguration, BaseConfiguration, BaseHierarchicalConfiguration, CombinedConfiguration, CompositeConfiguration, DatabaseConfiguration, DataConfiguration, DynamicCombinedConfiguration, EnvironmentConfiguration, INIConfiguration, JNDIConfiguration, JSONConfiguration, MapConfiguration, PatternSubtreeConfigurationWrapper, PropertiesConfiguration, PropertyListConfiguration, ServletConfiguration, ServletContextConfiguration, ServletFilterConfiguration, ServletRequestConfiguration, SubnodeConfiguration, SubsetConfiguration, SystemConfiguration, XMLConfiguration, XMLPropertiesConfiguration, XMLPropertyListConfiguration, YAMLConfiguration
public interface Configuration extends ImmutableConfiguration, SynchronizerSupport

The main Configuration interface.

This interface allows accessing and manipulating a configuration object. The major part of the methods defined in this interface deals with accessing properties of various data types. There is a generic getProperty() method, which returns the value of the queried property in its raw data type. Other getter methods try to convert this raw data type into a specific data type. If this fails, a ConversionException will be thrown.

For most of the property getter methods an overloaded version exists that allows to specify a default value, which will be returned if the queried property cannot be found in the configuration. The behavior of the methods that do not take a default value in case of a missing property is not defined by this interface and depends on a concrete implementation. E.g. the AbstractConfiguration class, which is the base class of most configuration implementations provided by this package, per default returns null if a property is not found, but provides the setThrowExceptionOnMissing() method, with which it can be configured to throw a NoSuchElementException exception in that case. (Note that getter methods for primitive types in AbstractConfiguration always throw an exception for missing properties because there is no way of overloading the return value.)

With the addProperty() and setProperty() methods new properties can be added to a configuration or the values of properties can be changed. With clearProperty() a property can be removed. Other methods allow to iterate over the contained properties or to create a subset configuration.

  • Method Details

    • addProperty

      void addProperty(String key, Object value)
      Add a property to the configuration. If it already exists then the value stated here will be added to the configuration entry. For example, if the property: 
       resource.loader = file
      is already present in the configuration and you call 
       addProperty("resource.loader", "classpath")
      Then you will end up with a List like the following: 
       ["file", "classpath"]
      Parameters:
      key - The key to add the property to.
      value - The value to add.

    • clear

      void clear()
      Remove all properties from the configuration.

    • clearProperty

      void clearProperty(String key)
      Remove a property from the configuration.
      Parameters:
      key - the key to remove along with corresponding value.

    • getInterpolator

      ConfigurationInterpolator getInterpolator()
      Gets the ConfigurationInterpolator object used by this Configuration. This object is responsible for variable substitution.
      Returns:
      the ConfigurationInterpolator (can be null)

    • installInterpolator

      void installInterpolator(Map<String,? extends Lookup> prefixLookups, Collection<? extends Lookup> defLookups)
      Creates and installs a new ConfigurationInterpolator for this Configuration based on the passed in arguments. This method creates a default ConfigurationInterpolator instance and initializes it with the passed in Lookup objects. It also adds a special default Lookup object that tries to resolve variables by matching them with properties contained in this Configuration. This is also the main difference to the setInterpolator(ConfigurationInterpolator) method which sets the passed in object as is without adding this special lookup.
      Parameters:
      prefixLookups - the map with Lookup objects associated with specific prefixes (can be null)
      defLookups - a collection with default Lookup objects (can be null)
      See Also:

    • setInterpolator

      void setInterpolator(ConfigurationInterpolator ci)
      Sets the ConfigurationInterpolator object to be used by this Configuration. This object is invoked for each access of a string property in order to substitute variables which may be contained. The argument can be null to disable interpolation at all.
      Parameters:
      ci - the new ConfigurationInterpolator

    • setProperty

      void setProperty(String key, Object value)
      Sets a property, this will replace any previously set values. Set values is implicitly a call to clearProperty(key), addProperty(key, value).
      Parameters:
      key - The key of the property to change
      value - The new value

    • subset

      Configuration subset(String prefix)
      Return a decorator Configuration containing every key from the current Configuration that starts with the specified prefix. The prefix is removed from the keys in the subset. For example, if the configuration contains the following properties: 
          prefix.number = 1
    prefix.string = Apache
    prefixed.foo = bar
    prefix = Jakarta
      the Configuration returned by subset("prefix") will contain the properties: 
          number = 1
    string = Apache
    = Jakarta
      (The key for the value "Jakarta" is an empty string)

      Since the subset is a decorator and not a modified copy of the initial Configuration, any change made to the subset is available to the Configuration, and reciprocally.

      Parameters:
      prefix - The prefix used to select the properties.
      Returns:
      a subset configuration
      See Also: