org.apache.commons.configuration2.builder.combined

Class BaseConfigurationBuilderProvider

java.lang.Object

org.apache.commons.configuration2.builder.combined.BaseConfigurationBuilderProvider

All Implemented Interfaces:

ConfigurationBuilderProvider

Direct Known Subclasses:

CombinedConfigurationBuilderProvider, FileExtensionConfigurationBuilderProvider, MultiFileConfigurationBuilderProvider

public class BaseConfigurationBuilderProvider
extends Object
implements ConfigurationBuilderProvider

A fully-functional, reflection-based implementation of the ConfigurationBuilderProvider interface which can deal with the default tags defining configuration sources.

An instance of this class is initialized with the names of the ConfigurationBuilder class used by this provider and the concrete Configuration class. The ConfigurationBuilder class must be derived from BasicConfigurationBuilder. When asked for the builder object, an instance of the builder class is created and initialized from the bean declaration associated with the current configuration source.

ConfigurationBuilder objects are configured using parameter objects. When declaring configuration sources in XML it should not be necessary to define the single parameter objects. Rather, simple and complex properties are set in the typical way of a bean declaration (i.e. as attributes of the current XML element or as child elements). This class creates all supported parameter objects (whose names also must be provided at construction time) and takes care that their properties are initialized according to the current bean declaration.

The use of reflection to create builder instances allows a generic implementation supporting many concrete builder classes. Another reason for this approach is that builder classes are only loaded if actually needed. Some specialized Configuration implementations require specific external dependencies which should not be mandatory for the use of CombinedConfigurationBuilder. Because such classes are lazily loaded, an application only has to include the dependencies it actually uses.

Since:

2.0

Constructor Summary

Constructors

Constructor and Description
BaseConfigurationBuilderProvider(String bldrCls, String reloadBldrCls, String configCls, Collection<String> paramCls) Creates a new instance of BaseConfigurationBuilderProvider and initializes all its properties.

Method Summary

Modifier and Type	Method and Description
protected void	configureBuilder(BasicConfigurationBuilder<? extends Configuration> builder, ConfigurationDeclaration decl, Collection<BuilderParameters> params) Configures a newly created builder instance with its initialization parameters.
protected BasicConfigurationBuilder<? extends Configuration>	createBuilder(ConfigurationDeclaration decl, Collection<BuilderParameters> params) Creates a new, uninitialized instance of the builder class managed by this provider.
protected Collection<BuilderParameters>	createParameterObjects() Creates a collection of parameter objects to be used for configuring the builder.
protected String	determineBuilderClass(ConfigurationDeclaration decl) Determines the name of the class to be used for a new builder instance.
protected String	determineConfigurationClass(ConfigurationDeclaration decl, Collection<BuilderParameters> params) Determines the name of the configuration class produced by the builder.
String	getBuilderClass() Returns the name of the class of the builder created by this provider.
ConfigurationBuilder<? extends Configuration>	getConfigurationBuilder(ConfigurationDeclaration decl) Returns the builder for the configuration source managed by this provider.
String	getConfigurationClass() Returns the name of the configuration class created by the builder produced by this provider.
Collection<String>	getParameterClasses() Returns an unmodifiable collection with the names of parameter classes supported by this provider.
String	getReloadingBuilderClass() Returns the name of the class of the builder created by this provider if the reload flag is set.
protected void	inheritParentBuilderProperties(ConfigurationDeclaration decl, Collection<BuilderParameters> params) Passes all parameter objects to the parent CombinedConfigurationBuilder so that properties already defined for the parent builder can be added.
protected void	initializeParameterObjects(ConfigurationDeclaration decl, Collection<BuilderParameters> params) Initializes the parameter objects with data stored in the current bean declaration.
protected boolean	isAllowFailOnInit(ConfigurationDeclaration decl) Determines the allowFailOnInit flag for the newly created builder based on the given ConfigurationDeclaration.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BaseConfigurationBuilderProvider

public BaseConfigurationBuilderProvider(String bldrCls,
                                        String reloadBldrCls,
                                        String configCls,
                                        Collection<String> paramCls)

Creates a new instance of BaseConfigurationBuilderProvider and initializes all its properties.

Parameters:

bldrCls - the name of the builder class (must not be null)

reloadBldrCls - the name of a builder class to be used if reloading support is required (null if reloading is not supported)

configCls - the name of the configuration class (must not be null)

paramCls - a collection with the names of parameters classes

Throws:

IllegalArgumentException - if a required parameter is missing

Method Detail

getBuilderClass

public String getBuilderClass()

Returns the name of the class of the builder created by this provider.

Returns:

the builder class

getReloadingBuilderClass

public String getReloadingBuilderClass()

Returns the name of the class of the builder created by this provider if the reload flag is set. If this method returns null, reloading builders are not supported by this provider.

Returns:

the reloading builder class

getConfigurationClass

public String getConfigurationClass()

Returns the name of the configuration class created by the builder produced by this provider.

Returns:

the configuration class

getParameterClasses

public Collection<String> getParameterClasses()

Returns an unmodifiable collection with the names of parameter classes supported by this provider.

Returns:

the parameter classes

getConfigurationBuilder

public ConfigurationBuilder<? extends Configuration> getConfigurationBuilder(ConfigurationDeclaration decl)
                                                                      throws ConfigurationException

Returns the builder for the configuration source managed by this provider. This method is called during processing of the combined configuration definition file. This implementation delegates to some protected methods to create a new builder instance using reflection and to configure it with parameter values defined by the passed in BeanDeclaration.

Specified by:

getConfigurationBuilder in interface ConfigurationBuilderProvider

Parameters:

decl - the bean declaration with initialization parameters for the configuration builder

Returns:

the ConfigurationBuilder object created by this provider

Throws:

ConfigurationException - if an error occurs

isAllowFailOnInit

protected boolean isAllowFailOnInit(ConfigurationDeclaration decl)

Determines the allowFailOnInit flag for the newly created builder based on the given ConfigurationDeclaration. Some combinations of flags in the declaration say that a configuration source is optional, but an empty instance should be created if its creation fail.

Parameters:

decl - the current ConfigurationDeclaration

Returns:

the value of the allowFailOnInit flag

createParameterObjects

protected Collection<BuilderParameters> createParameterObjects()
                                                        throws Exception

Creates a collection of parameter objects to be used for configuring the builder. This method creates instances of the parameter classes passed to the constructor.

Returns:

a collection with parameter objects for the builder

Throws:

Exception - if an error occurs while creating parameter objects via reflection

initializeParameterObjects

protected void initializeParameterObjects(ConfigurationDeclaration decl,
                                          Collection<BuilderParameters> params)
                                   throws Exception

Initializes the parameter objects with data stored in the current bean declaration. This method is called before the newly created builder instance is configured with the parameter objects. It maps attributes of the bean declaration to properties of parameter objects. In addition, it invokes the parent CombinedConfigurationBuilder so that the parameters object can inherit properties already defined for this builder.

Parameters:

decl - the current ConfigurationDeclaration

params - the collection with (uninitialized) parameter objects

Throws:

Exception - if an error occurs

inheritParentBuilderProperties

protected void inheritParentBuilderProperties(ConfigurationDeclaration decl,
                                              Collection<BuilderParameters> params)

Passes all parameter objects to the parent CombinedConfigurationBuilder so that properties already defined for the parent builder can be added. This method is called before the parameter objects are initialized from the definition configuration. This way properties from the parent builder are inherited, but can be overridden for child configurations.

Parameters:

decl - the current ConfigurationDeclaration

params - the collection with (uninitialized) parameter objects

createBuilder

protected BasicConfigurationBuilder<? extends Configuration> createBuilder(ConfigurationDeclaration decl,
                                                                           Collection<BuilderParameters> params)
                                                                    throws Exception

Creates a new, uninitialized instance of the builder class managed by this provider. This implementation determines the builder class to be used by delegating to determineBuilderClass(). It then calls the constructor expecting the configuration class, the map with properties, and theallowFailOnInit flag.

Parameters:

decl - the current ConfigurationDeclaration

params - initialization parameters for the new builder object

Returns:

the newly created builder instance

Throws:

Exception - if an error occurs

configureBuilder

protected void configureBuilder(BasicConfigurationBuilder<? extends Configuration> builder,
                                ConfigurationDeclaration decl,
                                Collection<BuilderParameters> params)
                         throws Exception

Configures a newly created builder instance with its initialization parameters. This method is called after a new instance was created using reflection. This implementation passes the parameter objects to the builder's configure() method.

Parameters:

builder - the builder to be initialized

decl - the current ConfigurationDeclaration

params - the collection with initialization parameter objects

Throws:

Exception - if an error occurs

determineBuilderClass

protected String determineBuilderClass(ConfigurationDeclaration decl)
                                throws ConfigurationException

Determines the name of the class to be used for a new builder instance. This implementation selects between the normal and the reloading builder class, based on the passed in ConfigurationDeclaration. If a reloading builder is desired, but this provider has no reloading support, an exception is thrown.

Parameters:

decl - the current ConfigurationDeclaration

Returns:

the name of the builder class

Throws:

ConfigurationException - if the builder class cannot be determined

determineConfigurationClass

protected String determineConfigurationClass(ConfigurationDeclaration decl,
                                             Collection<BuilderParameters> params)
                                      throws ConfigurationException

Determines the name of the configuration class produced by the builder. This method is called when obtaining the arguments for invoking the constructor of the builder class. This implementation just returns the pre-configured configuration class name. Derived classes may determine this class name dynamically based on the passed in parameters.

Parameters:

decl - the current ConfigurationDeclaration

params - the collection with parameter objects

Returns:

the name of the builder's result configuration class

Throws:

ConfigurationException - if an error occurs