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Commons Configuration Package
Version 2.0
Release Notes
This document contains the release notes for this version of the Commons
Configuration component. It describes the changes since the previous version.
The Commons Configuration software library provides a generic configuration
interface which enables an application to read configuration data from a variety
of sources.
After a series of alpha and beta releases (please consult the corresponding
release notes below), this is the first final release for Apache Commons
Configuration 2.0.
Version 2.0 is a complete redesign of the Configuration 1.x API with the aim to
fix some limitations in the original design and make the library more flexible
and powerful. Therefore, this release is not a drop-in replacement for Commons
Configuration 1.x; there have been incompatible changes in many areas that
require adaptations on client code. A migration guide is available at
that describes all breaking changes and helps when upgrading to the new
version. One obvious breaking change is the renaming of the main package
(all classes are now located under org.apache.commons.configuration2) and the
Maven coordinates (groupId: org.apache.commons, artifactId:
commons-configuration2). This was necessary to allow both versions to coexist
on the classpath without conflicts.
The user's guide has been completely reworked to describe all features of the
new version. It can be found at
Moved ConfigurationLogger class to io package to avoid cyclic dependencies
between packages.
CombinedConfigurationBuilder now supports inheritance of its parameters to
child configuration sources. This is enabled by default.
Changed generic types in the signatures of a MapConfiguration constructor
and AbstractConfiguration.getList(String, List). These changes were made in
version 1.10 as fixes for CONFIGURATION-557 and CONFIGURATION-558. But it
had been missed to merge them to trunk.
Fixed Bugs:
Fixed two invalid examples in the user's guide for file-based configurations.
When using immutable configurations exceptions thrown by the wrapped
configuration came out as UndeclaredThrowableException. This has been fixed;
now the correct original exception is thrown.
Commons Configuration 2.0 requires Java 1.6 or higher.
Historical list of changes:
For complete information on Apache Commons Configuration, including instructions
on how to submit bug reports, patches, or suggestions for improvement, see the
Apache Commons Configuration website:
Older release notes
Commons Configuration Package
Version 2.0-beta2
Release Notes
After the first beta release in June 2015 there has been some feedback from the
community resulting in (minor) adaptations of the API. In most cases, the
return values of methods have been changed to be more generic. There has also
been a change in the support for logging. Therefore, this second beta release
is provided to make these changes more "official".
This release also includes some bug fixes. The bugs addressed here have partly
existed already in the Configuration 1.0 code base; so these fixes are not all
related to changes introduced in the 2.0 version.
Below is a list of all changes in this version. Please refer to the clirr
report at
for information about changes which break binary compatibility.
References to Commons Logging have been removed from the Configuration API.
It is still possible to influence logging by making use of the new
ConfigurationLogger abstraction.
The return type of ConfigurationBuilder.getConfiguration() was changed from
Configuration to ImmutableConfiguration because this is the base interface
for all configuration objects. Thanks to Jon Weygand.
Adapted the return type of ReloadingFileBasedConfigurationBuilder.configure().
Fixed Bugs:
Fixed a bug in PropertiesConfiguration related to the loading of include
files. The FileHandler used for this purpose was not fully initialized.
XMLConfiguration no longer drops keys when list delimiter characters occur
in element values.
Fixed a problem in the conversion of a flat configuration to a hierarchical
one that could cause the loss of properties in a combined configuration
constructed by an override combiner.
Commons Configuration 2.0-beta2 requires Java 1.6 or higher.
Historical list of changes:
For complete information on Apache Commons Configuration, including instructions
on how to submit bug reports, patches, or suggestions for improvement, see the
Apache Commons Configuration website:
Commons Configuration Package
Version 2.0-beta1
Release Notes
This is the first beta release of Commons Configuration 2.0 after two alpha
versions. There has not been much feedback so far and no requests for API
changes. Therefore, we move forwards to a beta release indicating that the API
can be considered more stable. However, at this stage, changes of the API can
still not be fully excluded.
Below is a list of all changes in this version. Compared to version 2.0-alpha2,
there has only be a single change: an obsolete interface (which had been
overlooked during a major refactoring) was removed. So applications that are
using 2.0-alpha2 should be able to migrate to 2.0-beta1 without problems.
o CONFIGURATION-598: Removed obsolete ConfigurationBuilder interface in the
base package.
Commons Configuration Package
Version 2.0-alpha2
Release Notes
After version 2.0-alpha1 has been out for a while (the corresponding release
notes can be found below), this second alpha release contains a few number of
improvements and new features whose implementation required some changes on
existing interfaces. In most cases, new methods were added offering enhanced
functionality. Because these are typically interfaces implemented by the
library itself client code using the previous alpha version should hardly be
Below is a list of all changes in this version:
New features:
o CONFIGURATION-574: DefaultExpressionEngine can now be customized to match
configuration keys in a case-insensitive manner. This is useful
for instance for dealing with Windows INI files.
o CONFIGURATION-565: Added support for querying encoded properties.
o CONFIGURATION-200: A size() method was added to the ImmutableConfiguration interface.
Fixed Bugs:
o CONFIGURATION-564: PropertiesConfiguration now supports again properties without a
value and a separator character. The keys of such properties
are added to the configuration with an empty String as value.
o CONFIGURATION-427: XMLPropertyListConfiguration can now save arrays in the correct form.
Historical list of changes:
For complete information on Apache Commons Configuration, including instructions on how to submit bug reports,
patches, or suggestions for improvement, see the Apache Commons Configuration website:
Commons Configuration Package
Version 2.0-alpha1
Release Notes
This is the first alpha release for version 2.0 of Commons Configuration.
Version 2 is a major redesign of the Configuration API. It breaks compatibility
in many areas and, therefore, is not a drop-in replacement for Commons
Configuration 1.x. To allow collaboration with an older version of the library
(and to prevent jar and dependency hell), the top-level package and the Maven
coordinates have been changed. There is an upgrade guide available at
describing the most important breaking changes. Be sure to read this
document if you want to switch from a 1.x version to this new version. The
user's guide which can be found at
has been reworked to cover all the new and changed features.
The main purpose of this alpha release is to gather feedback from the
community about the reworked API. IT IS NOT YET PRODUCTION READY. It is
expected that there will still be some changes on the public API.
Below is a list of all changes in this version:
New features:
o CONFIGURATION-579: A migration guide has been created which supports when upgrading from
version 1.x to 2.0.
o CONFIGURATION-559: It is now possible to define default values for initialization
properties of configurations.
o CONFIGURATION-551: The data type conversion mechanism has been made extensible. There is a
new interface ConversionHandler which controls the data type conversions
available for a configuration object. By setting a custom implementation,
conversions can be adapted or extended.
o CONFIGURATION-550: Conversion to Character is now supported.
o CONFIGURATION-541: Multi-file configurations are no longer restricted to XML configuration
files. Arbitrary file-based configurations are now supported.
o CONFIGURATION-535: DatabaseConfiguration now provides get methods for querying its
properties defining the underlying database structures.
o CONFIGURATION-533: DatabaseConfiguration now automatically converts CLOBs to strings if
they appear in property values.
o CONFIGURATION-525: PropertiesConfiguration now keeps a comment at the bottom of a
properties file. A new footer property was added for reading and
writing this footer comment.
o CONFIGURATION-519: Configuration objects are now created via configuration builders. A new
API for configuration builders has been added.
o CONFIGURATION-517: Hierarchical configurations now provide methods to obtain sub
configurations for all child elements of a given key.
o CONFIGURATION-514: Bean declarations now support constructor invocations.
o CONFIGURATION-512: It is now possible to obtain an immutable view on a Configuration or
HierarchicalConfiguration object. New interfaces,
ImmutableConfiguration, and ImmutableHierarchicalConfiguration have
been introduced.
o CONFIGURATION-508: Generic get() methods have been added to the Configuration interface.
These methods expect a target class and try to convert the value of
the specified property to this target class.
o CONFIGURATION-204: With the new reloading mechanism automatic and periodic reloading checks
can be performed.
o CONFIGURATION-202: Reloading checks can now be performed in a background thread.
Fixed Bugs:
o CONFIGURATION-582: Fixed a StringIndexOutOfBoundsException in PropertiesConfigurationLayout
which was caused by lines containing only whitespace.
o CONFIGURATION-572: When a CombinedConfiguration is cleared it removes itself as change
listener from all child configurations. This fixes a possible memory
o CONFIGURATION-570: Fixed a possible ConcurrentModificationException when a SystemConfiguration
instance is passed to the append() or copy() methods.
o CONFIGURATION-567: XMLBeanDeclaration now escapes node names before they are used to
determine nested properties. Thanks to Shen liang.
o CONFIGURATION-591: Removed methods from ConfigurationConverter related to ExtendedProperties.
This class is no longer supported by recent versions of Commons
o CONFIGURATION-590: Removed Serializable interface from all configuration implementations.
Some configuration classes declared this interface without being
actually serializable.
o CONFIGURATION-588: The name of the top-level package and the maven coordinates have been
changed to allow a coexistence of Commons Configuration 1.x with 2.0.
o CONFIGURATION-584: The event mechanism has been reworked. There is now a generic event
listener interface which can be used to receive notifications from
multiple types of event sources.
o CONFIGURATION-578: The user's guide has been fully reworked to cover all new and enhanced
features of version 2.0.
o CONFIGURATION-577: The dependency to Commons Collections is no longer needed.
o CONFIGURATION-576: A new abstract base class for hierarchical configurations was introduced
which supports arbitrary hierarchical data structures. The type of the
nodes used by the configuration can now be specified as a generic type
argument. This makes the integration of other hierarchical structures
o CONFIGURATION-575: Hierarchical configurations now operate on immutable structures.
Data is no longer represented by ConfigurationNode objects. The
ImmutableNode class now serves as data container.
o CONFIGURATION-573: XPathExpressionEngine can now deal with namespace prefixes in node and
attribute names.
o CONFIGURATION-563: The DefaultExpressionEngine class is now immutable. An instance can be
shared between multiple configuration objects.
o CONFIGURATION-562: Improved the API of ExprLookup.
o CONFIGURATION-555: Fixed a bug in the handling of the xml:space attribute in
XMLConfiguration. The attribute is now also applied to the current
element, not only to sub elements.
o CONFIGURATION-554: BeanHelper is no longer a static utility class. Instances can be
created with a specific configuration of bean factories. There is still
a default instance which can be obtained via the BeanHelper.INSTANCE
o CONFIGURATION-553: The code for accessing configuration files has been reworked. Methods
related to locating configuration files have been moved from
ConfigurationUtils to a new FileLocatorUtils class. Customizable
strategy classes (implementing the new FileLocationStrategy) can be
used for searching for configuration files.
o CONFIGURATION-546: BeanHelper can now process BeanDefinitions initializing properties of
collection types of their target beans. Thanks to Justin Couch.
o CONFIGURATION-544: Added missing dependencies to build.xml. Thanks to Oliver Kopp.
o CONFIGURATION-542: The mechanism for synchronizing configurations has been completely
redesigned. It is now based on Synchronizer objects which can be
configured by client code. A new chapter was added to the user's guide
regarding thread-safety of configurations.
o CONFIGURATION-540: MapConfiguration now directly uses a Properties object passed to its
constructor as data store rather than copying it. This allows
SystemConfiguration to be connected to system properties; i.e.
changing a property through SystemConfiguration immediately affects
the corresponding system property.
o CONFIGURATION-539: The deprecated INIConfiguration class was removed.
HierarchicalINIConfiguration was renamed to INIConfiguration.
o CONFIGURATION-537: The deprecated ConfigurationFactory class was removed.
o CONFIGURATION-536: File-based configurations are now implemented in a different way.
The interfaces FileConfiguration and ReloadingStrategy have been
removed, also the base classes AbstractFileConfiguration and
AbstractHierarchicalFileConfiguration. They are replaced by the
FileBased interface and the FileHandler class which implements
central I/O functionality. Reloading is now in the responsibility of
configuration builders.
o CONFIGURATION-534: The includesAllowed property of PropertyConfiguration is now independent
from the existence of a base path.
o CONFIGURATION-530: Concurrent access to configurations and reloading have been completely
redesigned. Because reloading is now handled by configuration builders
there is no need to acquire a lock in order to protected against a
reload operations.
o CONFIGURATION-527: AbstractConfiguration.clearPropertyDirect() is now abstract. Thanks to Matthias Richter.
o CONFIGURATION-526: XMLPropertiesConfiguration now supports loading from and saving to DOM
nodes. Thanks to Oliver Kopp.
o CONFIGURATION-524: Interpolation now works correctly after a configuration was cloned.
The ConfigurationInterpolator instance is now cloned, too.
o CONFIGURATION-521: ConfigurationUtils.fileFromUrl() now correctly handles URL containing
encoded percent characters. Thanks to Oliver Kopp.
o CONFIGURATION-520: Support for reloading of configuration data has been reworked.
o CONFIGURATION-518: Classes and interfaces related to interpolation have been slightly
reworked. ConfigurationInterpolator is now thread-safe. There are
multiple ways to define the ConfigurationInterpolator object to be
used by an AbstractConfiguration instance.
o CONFIGURATION-516: PropertiesConfiguration no longer escapes double quotes on saving.
o CONFIGURATION-515: The visibility of some internal methods of PropertiesConfiguration.PropertiesWriter
has been increased to protected. This simplifies the implementation of
a custom escaping strategy.
o CONFIGURATION-513: HierarchicalConfiguration is now an interface. The base implementation
class is named BaseHierarchicalConfiguration.
o CONFIGURATION-506: Removed obsolete nested classes Node and NodeVisitor of
HierarchicalConfiguration. The related deprecated class
ConfigurationKey was removed, too.
o CONFIGURATION-505: XMLConfiguration no longer supports attributes with multiple values or
list delimiter parsing in attributes. This feature was complex and
error prone and brought little value to the user.
o CONFIGURATION-504: SubnodeConfiguration now provides a new method for clearing it and
removing its root node from the parent configuration. The method
HierarchicalConfiguration.configurationsAt() now returns a list
of SubnodeConfiguration so that it is easier to make direct use of
this feature.
o CONFIGURATION-500: XMLConfiguration now adds attributes of elements defining a list to
all list nodes.
o CONFIGURATION-496: Concurrent access to configurations and reloading have been completely
redesigned. This should reduce the amount of synchronization.
o CONFIGURATION-486: Removed some static fields for specifying global default values.
Using static fields in this way is thread-hostile. There are now
alternatives for setting default values.
o CONFIGURATION-462: Updated dependency to Commons Lang from version 2.6 to 3.1.
o CONFIGURATION-419: EventSource is now an interface. With BaseEventSource there is a
default implementation.
o CONFIGURATION-418: The handling of list delimiters and their escape characters has been
reworked. A new ListDelimiterHandler interface was introduced allowing
applications to customize the treatment of list delimiters.
o CONFIGURATION-330: Concurrent access to configurations has been reworked.
o CONFIGURATION-153: It is now possible to define the strategy used for locating
configuration files.
o CONFIGURATION-136: Reloading can no longer corrupt a configuration instance. This is now
handled by a configuration builder; the original configuration instance
is not modified.
o CONFIGURATION-26: It is now possible to influence the conversion from a container object
(a collection or an array) to a single value (e.g. what is returned by
getString() if the current property has multiple values). Per default,
the first value is returned. By overriding methods of the
configuration's ConversionHandler, this behavior can be changed.
Historical list of changes:
For complete information on Apache Commons Configuration, including instructions on how to submit bug reports,
patches, or suggestions for improvement, see the Apache Commons Configuration website: