org.apache.commons.configuration2.beanutils

Class BeanHelper

java.lang.Object

org.apache.commons.configuration2.beanutils.BeanHelper

public final class BeanHelper
extends Object

A helper class for creating bean instances that are defined in configuration files.

This class provides utility methods related to bean creation operations. These methods simplify such operations because a client need not deal with all involved interfaces. Usually, if a bean declaration has already been obtained, a single method call is necessary to create a new bean instance.

This class also supports the registration of custom bean factories. Implementations of the BeanFactory interface can be registered under a symbolic name using the registerBeanFactory() method. In the configuration file the name of the bean factory can be specified in the bean declaration. Then this factory will be used to create the bean.

In order to create beans using BeanHelper, create and instance of this class and initialize it accordingly - a default BeanFactory can be passed to the constructor, and additional bean factories can be registered (see above). Then this instance can be used to create beans from BeanDeclaration objects. BeanHelper is thread-safe. So an instance can be passed around in an application and shared between multiple components.

Since:

1.3

Field Summary

Fields

Modifier and Type	Field and Description
static BeanHelper	INSTANCE A default instance of BeanHelper which can be shared between arbitrary components.

Constructor Summary

Constructors

Constructor and Description
BeanHelper() Creates a new instance of BeanHelper with the default instance of DefaultBeanFactory as default BeanFactory.
BeanHelper(BeanFactory defFactory) Creates a new instance of BeanHelper and sets the specified default BeanFactory.

Method Summary

Modifier and Type	Method and Description
static void	copyProperties(Object dest, Object orig) Copies matching properties from the source bean to the destination bean using a specially configured PropertyUtilsBean instance.
Object	createBean(BeanDeclaration data) Returns a bean instance for the specified declaration.
Object	createBean(BeanDeclaration data, Class<?> defaultClass) Returns a bean instance for the specified declaration.
Object	createBean(BeanDeclaration data, Class<?> defaultClass, Object param) The main method for creating and initializing beans from a configuration.
static org.apache.commons.beanutils.DynaBean	createWrapDynaBean(Object bean) Creates a DynaBean instance which wraps the passed in bean.
BeanFactory	deregisterBeanFactory(String name) Deregisters the bean factory with the given name.
BeanFactory	getDefaultBeanFactory() Returns the default bean factory.
void	initBean(Object bean, BeanDeclaration data) Initializes the passed in bean.
static void	initBeanProperties(Object bean, BeanDeclaration data) Initializes the beans properties.
void	registerBeanFactory(String name, BeanFactory factory) Register a bean factory under a symbolic name.
Set<String>	registeredFactoryNames() Returns a set with the names of all currently registered bean factories.
static void	setProperty(Object bean, String propName, Object value) Set a property on the bean only if the property exists

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final BeanHelper INSTANCE

A default instance of BeanHelper which can be shared between arbitrary components. If no special configuration is needed, this instance can be used throughout an application. Otherwise, new instances can be created with their own configuration.

Constructor Detail

BeanHelper

public BeanHelper()

Creates a new instance of BeanHelper with the default instance of DefaultBeanFactory as default BeanFactory.

BeanHelper

public BeanHelper(BeanFactory defFactory)

Creates a new instance of BeanHelper and sets the specified default BeanFactory.

Parameters:

defFactory - the default BeanFactory (can be null, then a default instance is used)

Method Detail

registerBeanFactory

public void registerBeanFactory(String name,
                                BeanFactory factory)

Register a bean factory under a symbolic name. This factory object can then be specified in bean declarations with the effect that this factory will be used to obtain an instance for the corresponding bean declaration.

Parameters:

name - the name of the factory

factory - the factory to be registered

deregisterBeanFactory

public BeanFactory deregisterBeanFactory(String name)

Deregisters the bean factory with the given name. After that this factory cannot be used any longer.

Parameters:

name - the name of the factory to be deregistered

Returns:

the factory that was registered under this name; null if there was no such factory

registeredFactoryNames

public Set<String> registeredFactoryNames()

Returns a set with the names of all currently registered bean factories.

Returns:

a set with the names of the registered bean factories

getDefaultBeanFactory

public BeanFactory getDefaultBeanFactory()

Returns the default bean factory.

Returns:

the default bean factory

initBean

public void initBean(Object bean,
                     BeanDeclaration data)

Initializes the passed in bean. This method will obtain all the bean's properties that are defined in the passed in bean declaration. These properties will be set on the bean. If necessary, further beans will be created recursively.

Parameters:

bean - the bean to be initialized

data - the bean declaration

Throws:

ConfigurationRuntimeException - if a property cannot be set

initBeanProperties

public static void initBeanProperties(Object bean,
                                      BeanDeclaration data)

Initializes the beans properties.

Parameters:

bean - the bean to be initialized

data - the bean declaration

Throws:

ConfigurationRuntimeException - if a property cannot be set

createWrapDynaBean

public static org.apache.commons.beanutils.DynaBean createWrapDynaBean(Object bean)

Creates a DynaBean instance which wraps the passed in bean.

Parameters:

bean - the bean to be wrapped (must not be null)

Returns:

a DynaBean wrapping the passed in bean

Throws:

IllegalArgumentException - if the bean is null

Since:

2.0

copyProperties

public static void copyProperties(Object dest,
                                  Object orig)
                           throws IllegalAccessException,
                                  InvocationTargetException,
                                  NoSuchMethodException

Copies matching properties from the source bean to the destination bean using a specially configured PropertyUtilsBean instance. This method ensures that enhanced introspection is enabled when doing the copy operation.

Parameters:

dest - the destination bean

orig - the source bean

Throws:

NoSuchMethodException - exception thrown by PropertyUtilsBean

InvocationTargetException - exception thrown by PropertyUtilsBean

IllegalAccessException - exception thrown by PropertyUtilsBean

Since:

2.0

setProperty

public static void setProperty(Object bean,
                               String propName,
                               Object value)

Set a property on the bean only if the property exists

Parameters:

bean - the bean

propName - the name of the property

value - the property's value

Throws:

ConfigurationRuntimeException - if the property is not writeable or an error occurred

createBean

public Object createBean(BeanDeclaration data,
                         Class<?> defaultClass,
                         Object param)

The main method for creating and initializing beans from a configuration. This method will return an initialized instance of the bean class specified in the passed in bean declaration. If this declaration does not contain the class of the bean, the passed in default class will be used. From the bean declaration the factory to be used for creating the bean is queried. The declaration may here return null, then a default factory is used. This factory is then invoked to perform the create operation.

Parameters:

data - the bean declaration

defaultClass - the default class to use

param - an additional parameter that will be passed to the bean factory; some factories may support parameters and behave different depending on the value passed in here

Returns:

the new bean

Throws:

ConfigurationRuntimeException - if an error occurs

createBean

public Object createBean(BeanDeclaration data,
                         Class<?> defaultClass)

Returns a bean instance for the specified declaration. This method is a short cut for createBean(data, null, null);.

Parameters:

data - the bean declaration

defaultClass - the class to be used when in the declaration no class is specified

Returns:

the new bean

Throws:

ConfigurationRuntimeException - if an error occurs

createBean

public Object createBean(BeanDeclaration data)

Returns a bean instance for the specified declaration. This method is a short cut for createBean(data, null);.

Parameters:

data - the bean declaration

Returns:

the new bean

Throws:

ConfigurationRuntimeException - if an error occurs