Package org.apache.commons.configuration2

Class CompositeConfiguration

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

CompositeConfiguration allows you to add multiple Configuration objects to an aggregated configuration. If you add Configuration1, and then Configuration2, any properties shared will mean that the value defined by Configuration1 will be returned. If Configuration1 doesn't have the property, then Configuration2 will be checked. You can add multiple different types or the same type of properties file.

When querying properties the order in which child configurations have been added is relevant. To deal with property updates, a so-called in-memory configuration is used. Per default, such a configuration is created automatically. All property writes target this special configuration. There are constructors which allow you to provide a specific in-memory configuration. If used that way, the in-memory configuration is always the last one in the list of child configurations. This means that for query operations all other configurations take precedence.

Alternatively it is possible to mark a child configuration as in-memory configuration when it is added. In this case the treatment of the in-memory configuration is slightly different: it remains in the list of child configurations at the position it was added, i.e. its priority for property queries can be defined by adding the child configurations in the correct order.

This configuration class uses a Synchronizer to control concurrent access. While all methods for reading and writing configuration properties make use of this Synchronizer per default, the methods for managing the list of child configurations and the in-memory configuration (addConfiguration(), getNumberOfConfigurations(), removeConfiguration(), getConfiguration(), getInMemoryConfiguration()) are guarded, too. Because most methods for accessing configuration data delegate to the list of child configurations, the thread-safety of a CompositeConfiguration object also depends on the Synchronizer objects used by these children.

  • Constructor Details

    • CompositeConfiguration

      public CompositeConfiguration()
      Creates an empty CompositeConfiguration object which can then be added some other Configuration files

    • CompositeConfiguration

      public CompositeConfiguration(Collection<? extends Configuration> configurations)
      Create a CompositeConfiguration with an empty in memory configuration and adds the collection of configurations specified.
      Parameters:
      configurations - the collection of configurations to add

    • CompositeConfiguration

      public CompositeConfiguration(Configuration inMemoryConfiguration)
      Creates a CompositeConfiguration object with a specified in-memory configuration. This configuration will store any changes made to the CompositeConfiguration. Note: Use this constructor if you want to set a special type of in-memory configuration. If you have a configuration which should act as both a child configuration and as in-memory configuration, use addConfiguration(Configuration, boolean) with a value of true instead.
      Parameters:
      inMemoryConfiguration - the in memory configuration to use

    • CompositeConfiguration

      public CompositeConfiguration(Configuration inMemoryConfiguration, Collection<? extends Configuration> configurations)
      Creates a CompositeConfiguration with a specified in-memory configuration, and then adds the given collection of configurations.
      Parameters:
      inMemoryConfiguration - the in memory configuration to use
      configurations - the collection of configurations to add
      See Also:

  • Method Details

    • addConfiguration

      public void addConfiguration(Configuration config)
      Add a configuration.
      Parameters:
      config - the configuration to add

    • addConfiguration

      public void addConfiguration(Configuration config, boolean asInMemory)
      Adds a child configuration and optionally makes it the in-memory configuration. This means that all future property write operations are executed on this configuration. Note that the current in-memory configuration is replaced by the new one. If it was created automatically or passed to the constructor, it is removed from the list of child configurations! Otherwise, it stays in the list of child configurations at its current position, but it passes its role as in-memory configuration to the new one.
      Parameters:
      config - the configuration to be added
      asInMemory - true if this configuration becomes the new in-memory configuration, false otherwise
      Since:
      1.8

    • addConfigurationFirst

      public void addConfigurationFirst(Configuration config)
      Add a configuration to the start of the list of child configurations.
      Parameters:
      config - the configuration to add
      Since:
      2.3

    • addConfigurationFirst

      public void addConfigurationFirst(Configuration config, boolean asInMemory)
      Adds a child configuration to the start of the collection and optionally makes it the in-memory configuration. This means that all future property write operations are executed on this configuration. Note that the current in-memory configuration is replaced by the new one. If it was created automatically or passed to the constructor, it is removed from the list of child configurations! Otherwise, it stays in the list of child configurations at its current position, but it passes its role as in-memory configuration to the new one.
      Parameters:
      config - the configuration to be added
      asInMemory - true if this configuration becomes the new in-memory configuration, false otherwise
      Since:
      2.3

    • addPropertyDirect

      protected void addPropertyDirect(String key, Object token)
      Add this property to the in-memory Configuration.
      Specified by:
      addPropertyDirect in class AbstractConfiguration
      Parameters:
      key - The Key to add the property to.
      token - The Value to add.

    • clearInternal

      protected void clearInternal()
      Removes all child configurations and reinitializes the in-memory configuration. Attention: A new in-memory configuration is created; the old one is lost.
      Overrides:
      clearInternal in class AbstractConfiguration

    • 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

    • clone

      public Object clone()
      Returns a copy of this object. This implementation will create a deep clone, i.e. all configurations contained in this composite will also be cloned. This only works if all contained configurations support cloning; otherwise a runtime exception will be thrown. Registered event handlers won't get cloned.
      Overrides:
      clone in class BaseEventSource
      Returns:
      the copy
      Since:
      1.3

    • 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

    • getConfiguration

      public Configuration getConfiguration(int index)
      Gets the configuration at the specified index.
      Parameters:
      index - The index of the configuration to retrieve
      Returns:
      the configuration at this index

    • getInMemoryConfiguration

      public Configuration getInMemoryConfiguration()
      Gets the "in memory configuration". In this configuration changes are stored.
      Returns:
      the in memory 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 key)
      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:
      key - the prefix for the keys to be taken into account
      Returns:
      an Iterator returning the filtered keys

    • getList

      public List<Object> getList(String key, List<?> defaultValue)
      Description copied from interface: ImmutableConfiguration
      Gets a List of strings associated with the given configuration key. If the key doesn't map to an existing object, the default value is returned.
      Specified by:
      getList in interface ImmutableConfiguration
      Overrides:
      getList in class AbstractConfiguration
      Parameters:
      key - The configuration key.
      defaultValue - The default value.
      Returns:
      The associated List of strings.
      See Also:

    • getNumberOfConfigurations

      public int getNumberOfConfigurations()
      Gets the number of configurations.
      Returns:
      the number of configuration

    • getPropertyInternal

      protected Object getPropertyInternal(String key)
      Read property from underlying composite
      Specified by:
      getPropertyInternal in class AbstractConfiguration
      Parameters:
      key - key to use for mapping
      Returns:
      object associated with the given configuration key.

    • getSource

      public Configuration getSource(String key)
      Gets the configuration source, in which the specified key is defined. This method will iterate over all existing child configurations and check whether they contain the specified key. The following constellations are possible:
      • If exactly one child configuration contains the key, this configuration is returned as the source configuration. This may be the in memory configuration (this has to be explicitly checked by the calling application).
      • If none of the child configurations contain the key, null is returned.
      • If the key is contained in multiple child configurations or if the key is null, a IllegalArgumentException is thrown. In this case the source configuration cannot be determined.
      Parameters:
      key - the key to be checked
      Returns:
      the source configuration of this key
      Throws:
      IllegalArgumentException - if the source configuration cannot be determined
      Since:
      1.5

    • getStringArray

      public String[] getStringArray(String key)
      Description copied from class: AbstractConfiguration
      Gets an array of strings associated with the given configuration key. If the key doesn't map to an existing object, an empty array is returned. When a property is added to a configuration, it is checked whether it contains multiple values. This is obvious if the added object is a list or an array. For strings the association ListDelimiterHandler is consulted to find out whether the string can be split into multiple values.
      Specified by:
      getStringArray in interface ImmutableConfiguration
      Overrides:
      getStringArray in class AbstractConfiguration
      Parameters:
      key - The configuration key.
      Returns:
      The associated string array if key is found.
      See Also:

    • 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

    • removeConfiguration

      public void removeConfiguration(Configuration config)
      Remove a configuration. The in memory configuration cannot be removed.
      Parameters:
      config - The configuration to remove

    • 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.

      This implementation ensures that the in memory configuration is correctly initialized.
      Overrides:
      setListDelimiterHandler in class AbstractConfiguration
      Parameters:
      listDelimiterHandler - the ListDelimiterHandler to be used (must not be null)