Class CombinedConfigurationBuilder
- All Implemented Interfaces:
ConfigurationBuilder<CombinedConfiguration>
,EventSource
- Direct Known Subclasses:
ReloadingCombinedConfigurationBuilder
A specialized ConfigurationBuilder
implementation that creates a CombinedConfiguration
from multiple
configuration sources defined by an XML-based configuration definition file.
This class provides an easy and flexible means for loading multiple configuration sources and combining the results
into a single configuration object. The sources to be loaded are defined in an XML document that can contain certain
tags representing the different supported configuration classes. If such a tag is found, a corresponding
ConfigurationBuilder
class is instantiated and initialized using the classes of the beanutils
package
(namely XMLBeanDeclaration
will be used to
extract the configuration's initialization parameters, which allows for complex initialization scenarios).
It is also possible to add custom tags to the configuration definition file. For this purpose an implementation of
CombinedConfigurationBuilderProvider
has to be created which is responsible for the creation of a
ConfigurationBuilder
associated with the custom tag. An instance of this class has to be registered at the
CombinedBuilderParametersImpl
object which is used to initialize this CombinedConfigurationBuilder
.
This provider will then be called when the corresponding custom tag is detected. For many default configuration
classes providers are already registered.
The configuration definition file has the following basic structure:
<configuration systemProperties="properties file name"> <header> <!-- Optional meta information about the combined configuration --> </header> <override> <!-- Declarations for override configurations --> </override> <additional> <!-- Declarations for union configurations --> </additional> </configuration>
The name of the root element (here configuration
) is arbitrary. The optional systemProperties
attribute identifies the path to a property file containing properties that should be added to the system properties.
If specified on the root element, the system properties are set before the rest of the configuration is processed.
There are two sections (both of them are optional) for declaring override and additional configurations. Configurations in the former section are evaluated in the order of their declaration, and properties of configurations declared earlier hide those of configurations declared later. Configurations in the latter section are combined to a union configuration, i.e. all of their properties are added to a large hierarchical configuration. Configuration declarations that occur as direct children of the root element are treated as override declarations.
Each configuration declaration consists of a tag whose name is associated with a
CombinedConfigurationBuilderProvider
. This can be one of the predefined tags like properties
, or
xml
, or a custom tag, for which a configuration builder provider was registered (as described above).
Attributes and sub elements with specific initialization parameters can be added. There are some reserved attributes
with a special meaning that can be used in every configuration declaration:
Attribute | Meaning |
---|---|
config-name |
Allows specifying a name for this configuration. This name can be used to obtain a reference to the configuration
from the resulting combined configuration (see below). It can also be passed to the getNamedBuilder(String)
method. |
config-at |
With this attribute an optional prefix can be specified for the properties of the corresponding configuration. |
config-optional |
Declares a configuration source as optional. This means that errors that occur when creating the configuration are ignored. |
config-reload |
Many configuration sources support a reloading mechanism. For those sources it is possible to enable reloading by providing this attribute with a value of true. |
The optional header section can contain some meta data about the created configuration itself. For instance,
it is possible to set further properties of the NodeCombiner
objects used for constructing the resulting
configuration.
The default configuration object returned by this builder is an instance of the CombinedConfiguration
class.
This allows for convenient access to the configuration objects maintained by the combined configuration (e.g. for
updates of single configuration objects). It has also the advantage that the properties stored in all declared
configuration objects are collected and transformed into a single hierarchical structure, which can be accessed using
different expression engines. The actual CombinedConfiguration
implementation can be overridden by specifying
the class in the config-class attribute of the result element.
A custom EntityResolver can be used for all XMLConfigurations by adding
<entity-resolver config-class="EntityResolver fully qualified class name">
A specific CatalogResolver can be specified for all XMLConfiguration sources by adding
<entity-resolver catalogFiles="comma separated list of catalog files">
Additional ConfigurationProviders can be added by configuring them in the header section.
<providers> <provider config-tag="tag name" config-class="provider fully qualified class name"/> </providers>
Additional variable resolvers can be added by configuring them in the header section.
<lookups> <lookup config-prefix="prefix" config-class="StrLookup fully qualified class name"/> </lookups>
All declared override configurations are directly added to the resulting combined configuration. If they are given
names (using the config-name
attribute), they can directly be accessed using the
getConfiguration(String)
method of CombinedConfiguration
. The additional configurations are
altogether added to another combined configuration, which uses a union combiner. Then this union configuration is
added to the resulting combined configuration under the name defined by the ADDITIONAL_NAME
constant. The
getNamedBuilder(String)
method can be used to access the ConfigurationBuilder
objects for all
configuration sources which have been assigned a name; care has to be taken that these names are unique.
- Since:
- 1.3
-
Field Summary
Modifier and TypeFieldDescriptionstatic final String
Constant for the name of the additional configuration. -
Constructor Summary
ConstructorDescriptionCreates a new instance ofCombinedConfigurationBuilder
.CombinedConfigurationBuilder
(Map<String, Object> params) Creates a new instance ofCombinedConfigurationBuilder
and sets the specified initialization parameters.CombinedConfigurationBuilder
(Map<String, Object> params, boolean allowFailOnInit) Creates a new instance ofCombinedConfigurationBuilder
and sets the specified initialization parameters and the allowFailOnInit flag. -
Method Summary
Modifier and TypeMethodDescriptionReturns a set with the names of all child configuration builders.configure
(BuilderParameters... params) Appends the content of the specifiedBuilderParameters
objects to the current initialization parameters.protected void
configureEntityResolver
(HierarchicalConfiguration<?> config, XMLBuilderParametersImpl xmlParams) Creates and initializes a defaultEntityResolver
if the definition configuration contains a corresponding declaration.protected CombinedConfiguration
createAdditionalsConfiguration
(CombinedConfiguration resultConfig) Creates theCombinedConfiguration
for the configuration sources in the<additional>
section.protected BeanDeclaration
createResultDeclaration
(Map<String, Object> params) Creates a newBeanDeclaration
which is used for creating new result objects dynamically.protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>>
createXMLDefinitionBuilder
(BuilderParameters builderParams) Creates a default builder for the definition configuration and initializes it with a parameters object.protected Collection<ConfigurationBuilder<? extends Configuration>>
Gets a collection with the builders for all child configuration sources.ConfigurationBuilder<? extends HierarchicalConfiguration<?>>
Gets theConfigurationBuilder
which creates the definition configuration.protected HierarchicalConfiguration<?>
Gets the configuration containing the definition of the combined configuration to be created.ConfigurationBuilder<? extends Configuration>
getNamedBuilder
(String name) Gets the configuration builder with the given name.protected void
Initializes a parameters object for a child builder.protected FileSystem
initFileSystem
(HierarchicalConfiguration<?> config) Creates and initializes a defaultFileSystem
if the definition configuration contains a corresponding declaration.protected void
Initializes a newly created result object.protected void
initSystemProperties
(HierarchicalConfiguration<?> config, String basePath) Handles a file with system properties that may be defined in the definition configuration.protected ConfigurationBuilderProvider
providerForTag
(String tagName) Returns theConfigurationBuilderProvider
for the given tag.protected void
registerConfiguredLookups
(HierarchicalConfiguration<?> defConfig, Configuration resultConfig) Processes customLookup
objects that might be declared in the definition configuration.void
Removes all initialization parameters of this builder.protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>>
setupDefinitionBuilder
(Map<String, Object> params) Obtains theConfigurationBuilder
object which provides access to the configuration containing the definition of the combined configuration to create.Methods inherited from class org.apache.commons.configuration2.builder.BasicConfigurationBuilder
addEventListener, addParameters, connectToReloadingController, copyEventListeners, copyEventListeners, createResult, createResultInstance, fetchBeanHelper, fireBuilderEvent, getConfiguration, getParameters, getResultClass, getResultDeclaration, installEventListener, isAllowFailOnInit, removeEventListener, reset, resetResult, setParameters
-
Field Details
-
ADDITIONAL_NAME
Constant for the name of the additional configuration. If the configuration definition file contains anadditional
section, a special union configuration is created and added under this name to the resulting combined configuration.
-
-
Constructor Details
-
CombinedConfigurationBuilder
public CombinedConfigurationBuilder()Creates a new instance ofCombinedConfigurationBuilder
. No parameters are set. -
CombinedConfigurationBuilder
Creates a new instance ofCombinedConfigurationBuilder
and sets the specified initialization parameters.- Parameters:
params
- a map with initialization parameters
-
CombinedConfigurationBuilder
Creates a new instance ofCombinedConfigurationBuilder
and sets the specified initialization parameters and the allowFailOnInit flag.- Parameters:
params
- a map with initialization parametersallowFailOnInit
- the allowFailOnInit flag
-
-
Method Details
-
builderNames
Returns a set with the names of all child configuration builders. A tag defining a configuration source in the configuration definition file can have the
config-name
attribute. If this attribute is present, the corresponding builder is assigned this name and can be directly accessed through thegetNamedBuilder(String)
method. This method returns a collection with all available builder names.Important note: This method only returns a meaningful result after the result configuration has been created by calling
getConfiguration()
. If called before, always an empty set is returned.- Returns:
- a set with the names of all builders
-
configure
Appends the content of the specifiedBuilderParameters
objects to the current initialization parameters. Calling this method multiple times will create a union of the parameters provided. This method is overridden to adapt the return type.- Overrides:
configure
in classBasicConfigurationBuilder<CombinedConfiguration>
- Parameters:
params
- an arbitrary number of objects with builder parameters- Returns:
- a reference to this builder for method chaining
-
configureEntityResolver
protected void configureEntityResolver(HierarchicalConfiguration<?> config, XMLBuilderParametersImpl xmlParams) throws ConfigurationException Creates and initializes a defaultEntityResolver
if the definition configuration contains a corresponding declaration.- Parameters:
config
- the definition configurationxmlParams
- the (already partly initialized) object with XML parameters; here the new resolver is to be stored- Throws:
ConfigurationException
- if an error occurs
-
createAdditionalsConfiguration
Creates theCombinedConfiguration
for the configuration sources in the<additional>
section. This method is called when the builder constructs the final configuration. It creates a newCombinedConfiguration
and initializes some properties from the result configuration.- Parameters:
resultConfig
- the result configuration (this is the configuration that will be returned by the builder)- Returns:
- the
CombinedConfiguration
for the additional configuration sources - Since:
- 1.7
-
createResultDeclaration
protected BeanDeclaration createResultDeclaration(Map<String, Object> params) throws ConfigurationExceptionCreates a newBeanDeclaration
which is used for creating new result objects dynamically. This implementation creates a specializedBeanDeclaration
object that is initialized from the given map of initialization parameters. TheBeanDeclaration
must be initialized with the result class of this builder, otherwise exceptions will be thrown when the result object is created. Note: This method is invoked in a synchronized block. This implementation evaluates theresult
property of the definition configuration. It creates a combined bean declaration with both the properties specified in the definition file and the properties defined as initialization parameters.- Overrides:
createResultDeclaration
in classBasicConfigurationBuilder<CombinedConfiguration>
- Parameters:
params
- a snapshot of the current initialization parameters- Returns:
- the
BeanDeclaration
for creating result objects - Throws:
ConfigurationException
- if an error occurs
-
createXMLDefinitionBuilder
protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> createXMLDefinitionBuilder(BuilderParameters builderParams) Creates a default builder for the definition configuration and initializes it with a parameters object. This method is called if no definition builder is defined in this builder's parameters. This implementation creates a default file-based builder which produces anXMLConfiguration
; it expects a corresponding file specification. Note: This method is called in a synchronized block.- Parameters:
builderParams
- the parameters object for the builder- Returns:
- the standard builder for the definition configuration
-
getChildBuilders
Gets a collection with the builders for all child configuration sources. This method can be used by derived classes providing additional functionality on top of the declared configuration sources. It only returns a defined value during construction of the result configuration instance.- Returns:
- a collection with the builders for child configuration sources
-
getDefinitionBuilder
public ConfigurationBuilder<? extends HierarchicalConfiguration<?>> getDefinitionBuilder() throws ConfigurationExceptionGets theConfigurationBuilder
which creates the definition configuration.- Returns:
- the builder for the definition configuration
- Throws:
ConfigurationException
- if an error occurs
-
getDefinitionConfiguration
Gets the configuration containing the definition of the combined configuration to be created. This method only returns a defined result during construction of the result configuration. The definition configuration is obtained from the definition builder at first access and then stored temporarily to ensure that during result construction always the same configuration instance is used. (Otherwise, it would be possible that the definition builder returns a different instance when queried multiple times.)- Returns:
- the definition configuration
- Throws:
ConfigurationException
- if an error occurs
-
getNamedBuilder
public ConfigurationBuilder<? extends Configuration> getNamedBuilder(String name) throws ConfigurationException Gets the configuration builder with the given name. With this method a builder of a child configuration which was given a name in the configuration definition file can be accessed directly.
Important note: This method only returns a meaningful result after the result configuration has been created by calling
getConfiguration()
. If called before, always an exception is thrown.- Parameters:
name
- the name of the builder in question- Returns:
- the child configuration builder with this name
- Throws:
ConfigurationException
- if information about named builders is not yet available or no builder with this name exists
-
initChildBuilderParameters
Initializes a parameters object for a child builder. This combined configuration builder has a bunch of properties which may be inherited by child configurations, e.g. the base path, the file system, etc. While processing the builders for child configurations, this method is called for each parameters object for a child builder. It initializes some properties of the passed in parameters objects which are derived from this parent builder.- Parameters:
params
- the parameters object to be initialized
-
initFileSystem
protected FileSystem initFileSystem(HierarchicalConfiguration<?> config) throws ConfigurationException Creates and initializes a defaultFileSystem
if the definition configuration contains a corresponding declaration. The file system returned by this method is used as default for all file-based child configuration sources.- Parameters:
config
- the definition configuration- Returns:
- the default
FileSystem
(may be null) - Throws:
ConfigurationException
- if an error occurs
-
initResultInstance
Initializes a newly created result object. This is the second step of the process of producing a result object for this builder. This implementation uses theBeanHelper
class to initialize the object's property based on theBeanDeclaration
returned byBasicConfigurationBuilder.getResultDeclaration()
. Note: This method is invoked in a synchronized block. This is required because internal state is accessed. Sub classes must not call this method without proper synchronization. This implementation processes the definition configuration in order to- initialize the resulting
CombinedConfiguration
- determine the builders for all configuration sources
- populate the resulting
CombinedConfiguration
- Overrides:
initResultInstance
in classBasicConfigurationBuilder<CombinedConfiguration>
- Parameters:
result
- the object to be initialized- Throws:
ConfigurationException
- if an error occurs
- initialize the resulting
-
initSystemProperties
protected void initSystemProperties(HierarchicalConfiguration<?> config, String basePath) throws ConfigurationException Handles a file with system properties that may be defined in the definition configuration. If such property file is configured, all of its properties are added to the system properties.- Parameters:
config
- the definition configurationbasePath
- the base path defined for this builder (may be null)- Throws:
ConfigurationException
- if an error occurs.
-
providerForTag
Returns theConfigurationBuilderProvider
for the given tag. This method is called during creation of the result configuration. (It is not allowed to call it at another point of time; result is then unpredictable!) It supports all default providers and custom providers added through the parameters object as well.- Parameters:
tagName
- the name of the tag- Returns:
- the provider that was registered for this tag or null if there is none
-
registerConfiguredLookups
protected void registerConfiguredLookups(HierarchicalConfiguration<?> defConfig, Configuration resultConfig) throws ConfigurationException Processes customLookup
objects that might be declared in the definition configuration. EachLookup
object is registered at the definition configuration and at the result configuration. It is also added to all child configurations added to the resulting combined configuration.- Parameters:
defConfig
- the definition configurationresultConfig
- the resulting configuration- Throws:
ConfigurationException
- if an error occurs
-
resetParameters
Removes all initialization parameters of this builder. This method can be called if this builder is to be reused for creating result objects with a different configuration. This implementation resets some specific internal state of this builder.- Overrides:
resetParameters
in classBasicConfigurationBuilder<CombinedConfiguration>
-
setupDefinitionBuilder
protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> setupDefinitionBuilder(Map<String, Object> params) throws ConfigurationExceptionObtains theConfigurationBuilder
object which provides access to the configuration containing the definition of the combined configuration to create. If a definition builder is defined in the parameters, it is used. Otherwise, we check whether the combined builder parameters object contains a parameters object for the definition builder. If this is the case, a builder for anXMLConfiguration
is created and configured with this object. As a last resort, it is looked for aFileBasedBuilderParametersImpl
object in the properties. If found, also a XML configuration builder is created which loads this file. Note: This method is called from a synchronized block.- Parameters:
params
- the current parameters for this builder- Returns:
- the builder for the definition configuration
- Throws:
ConfigurationException
- if an error occurs
-