Package org.apache.commons.configuration2

Class SubsetConfiguration

java.lang.Object
org.apache.commons.configuration2.event.BaseEventSource
org.apache.commons.configuration2.AbstractConfiguration
org.apache.commons.configuration2.SubsetConfiguration
All Implemented Interfaces:
Configuration, EventSource, ImmutableConfiguration, SynchronizerSupport
public class SubsetConfiguration extends AbstractConfiguration

A subset of another configuration. The new Configuration object contains every key from the parent Configuration that starts with prefix. The prefix is removed from the keys in the subset.

It is usually not necessary to use this class directly. Instead the Configuration.subset(String) method should be used, which will return a correctly initialized instance.

  • Field Details

  • Constructor Details

    • SubsetConfiguration

      public SubsetConfiguration(Configuration parent, String prefix)
      Create a subset of the specified configuration
      Parameters:
      parent - The parent configuration (must not be null)
      prefix - The prefix used to select the properties
      Throws:
      IllegalArgumentException - if the parent configuration is null

    • SubsetConfiguration

      public SubsetConfiguration(Configuration parent, String prefix, String delimiter)
      Create a subset of the specified configuration
      Parameters:
      parent - The parent configuration (must not be null)
      prefix - The prefix used to select the properties
      delimiter - The prefix delimiter
      Throws:
      NullPointerException - if the parent configuration is null

  • Method Details

    • addPropertyDirect

      public void addPropertyDirect(String key, Object value)
      Description copied from class: AbstractConfiguration
      Adds a key/value pair to the Configuration. Override this method to provide write access to underlying Configuration store.
      Specified by:
      addPropertyDirect in class AbstractConfiguration
      Parameters:
      key - key to use for mapping
      value - object to store

    • clearPropertyDirect

      protected void clearPropertyDirect(String key)
      Description copied from class: AbstractConfiguration
      Removes the specified property from this configuration. This method is called by clearProperty() after it has done some preparations. It must be overridden in sub classes.
      Specified by:
      clearPropertyDirect in class AbstractConfiguration
      Parameters:
      key - the key to be removed

    • containsKeyInternal

      protected boolean containsKeyInternal(String key)
      Description copied from class: AbstractConfiguration
      Actually checks whether the specified key is contained in this configuration. This method is called by containsKey(). It has to be defined by concrete subclasses.
      Specified by:
      containsKeyInternal in class AbstractConfiguration
      Parameters:
      key - the key in question
      Returns:
      true if this key is contained in this configuration, false otherwise

    • containsValueInternal

      protected boolean containsValueInternal(Object value)
      Tests whether this configuration contains one or more matches to this value. This operation stops at first match but may be more expensive than the containsKey method.
      Specified by:
      containsValueInternal in class AbstractConfiguration
      Parameters:
      value - the value in question
      Returns:
      true if and only if some key maps to the value argument in this configuration as determined by the equals method; false otherwise.
      Since:
      2.11.0

    • getChildKey

      protected String getChildKey(String key)
      Gets the key in the subset configuration associated to the specified key in the parent configuration.
      Parameters:
      key - The key in the parent configuration.
      Returns:
      the key in the context of this subset configuration

    • getKeysInternal

      protected Iterator<String> getKeysInternal()
      Description copied from class: AbstractConfiguration
      Actually creates an iterator for iterating over the keys in this configuration. This method is called by getKeys(), it has to be defined by concrete subclasses.
      Specified by:
      getKeysInternal in class AbstractConfiguration
      Returns:
      an Iterator with all property keys in this configuration

    • getKeysInternal

      protected Iterator<String> getKeysInternal(String prefix)
      Description copied from class: AbstractConfiguration
      Gets an Iterator with all property keys starting with the specified prefix. This method is called by AbstractConfiguration.getKeys(String). It is fully implemented by delegating to getKeysInternal() and returning a special iterator which filters for the passed in prefix. Subclasses can override it if they can provide a more efficient way to iterate over specific keys only.
      Overrides:
      getKeysInternal in class AbstractConfiguration
      Parameters:
      prefix - the prefix for the keys to be taken into account
      Returns:
      an Iterator returning the filtered keys

    • getListDelimiterHandler

      public ListDelimiterHandler getListDelimiterHandler()
      Gets the ListDelimiterHandler used by this instance. If the parent configuration extends AbstractConfiguration, the list delimiter handler is obtained from there.
      Overrides:
      getListDelimiterHandler in class AbstractConfiguration
      Returns:
      the ListDelimiterHandler

    • getParent

      public Configuration getParent()
      Gets the parent configuration for this subset.
      Returns:
      the parent configuration

    • getParentKey

      protected String getParentKey(String key)
      Gets the key in the parent configuration associated to the specified key in this subset.
      Parameters:
      key - The key in the subset.
      Returns:
      the key as to be used by the parent

    • getPrefix

      public String getPrefix()
      Gets the prefix used to select the properties in the parent configuration.
      Returns:
      the prefix used by this subset

    • getPropertyInternal

      protected Object getPropertyInternal(String key)
      Description copied from class: AbstractConfiguration
      Actually obtains the value of the specified property. This method is called by getProperty(). Concrete subclasses must define it to fetch the value of the desired property.
      Specified by:
      getPropertyInternal in class AbstractConfiguration
      Parameters:
      key - the key of the property in question
      Returns:
      the (raw) value of this property

    • isEmptyInternal

      protected boolean isEmptyInternal()
      Description copied from class: AbstractConfiguration
      Actually checks whether this configuration contains data. This method is called by isEmpty(). It has to be defined by concrete subclasses.
      Specified by:
      isEmptyInternal in class AbstractConfiguration
      Returns:
      true if this configuration contains no data, false otherwise

    • isThrowExceptionOnMissing

      public boolean isThrowExceptionOnMissing()
      Returns true if missing values throw Exceptions. The subset inherits this feature from its parent if it supports this feature.
      Overrides:
      isThrowExceptionOnMissing in class AbstractConfiguration
      Returns:
      true if missing values throw Exceptions

    • setListDelimiterHandler

      public void setListDelimiterHandler(ListDelimiterHandler listDelimiterHandler)

      Sets the ListDelimiterHandler to be used by this instance. This object is invoked every time when dealing with string properties that may contain a list delimiter and thus have to be split to multiple values. Per default, a ListDelimiterHandler implementation is set which does not support list splitting. This can be changed for instance by setting a DefaultListDelimiterHandler object.

      Warning: Be careful when changing the list delimiter handler when the configuration has already been loaded/populated. List handling is typically applied already when properties are added to the configuration. If later another handler is set which processes lists differently, results may be unexpected; some operations may even cause exceptions.

      If the parent configuration extends AbstractConfiguration, the list delimiter handler is passed to the parent.
      Overrides:
      setListDelimiterHandler in class AbstractConfiguration
      Parameters:
      listDelimiterHandler - the ListDelimiterHandler to be used (must not be null)

    • setPrefix

      public void setPrefix(String prefix)
      Sets the prefix used to select the properties in the parent configuration.
      Parameters:
      prefix - the prefix

    • setThrowExceptionOnMissing

      public void setThrowExceptionOnMissing(boolean throwExceptionOnMissing)
      Allows to set the throwExceptionOnMissing flag. This flag controls the behavior of property getter methods that return objects if the requested property is missing. If the flag is set to false (which is the default value), these methods will return null. If set to true, they will throw a NoSuchElementException exception. Note that getter methods for primitive data types are not affected by this flag. Change the behavior of the parent configuration if it supports this feature.
      Overrides:
      setThrowExceptionOnMissing in class AbstractConfiguration
      Parameters:
      throwExceptionOnMissing - The new value for the property

    • subset

      public Configuration subset(String prefix)
      Description copied from interface: Configuration
      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.

      Specified by:
      subset in interface Configuration
      Overrides:
      subset in class AbstractConfiguration
      Parameters:
      prefix - The prefix used to select the properties.
      Returns:
      a subset configuration
      See Also: