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## org.apache.commons.configuration.beanutils
Class BeanHelper

    java.lang.Object
      org.apache.commons.configuration.beanutils.BeanHelper

    public final class BeanHelper

extends Object

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

This class provides static 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.

Since:
  1.3
Version:
  $Id: BeanHelper.java 1208762 2011-11-30 20:40:32Z oheger $
Author:
  Commons Configuration team

Method Summary
`static Object` | `createBean(BeanDeclaration data)` Returns a bean instance for the specified declaration.
`static Object` | `createBean(BeanDeclaration data, Class<?> defaultClass)` Returns a bean instance for the specified declaration.
`static Object` | `createBean(BeanDeclaration data, Class<?> defaultClass, Object param)` The main method for creating and initializing beans from a configuration.
`static BeanFactory` | `deregisterBeanFactory(String name)` Deregisters the bean factory with the given name.
`static BeanFactory` | `getDefaultBeanFactory()` Returns the default bean factory.
`static void` | `initBean(Object bean, BeanDeclaration data)` Initializes the passed in bean.
`static void` | `initBeanProperties(Object bean, BeanDeclaration data)` Initializes the beans properties.
`static void` | `registerBeanFactory(String name, BeanFactory factory)` Register a bean factory under a symbolic name.
`static Set<String>` | `registeredFactoryNames()` Returns a set with the names of all currently registered bean factories.
`static void` | `setDefaultBeanFactory(BeanFactory factory)` Sets the default bean factory.
`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`

Method Detail

### registerBeanFactory

    public static 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 static 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 static 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 static BeanFactory getDefaultBeanFactory()

  Returns the default bean factory.

  Returns:
    the default bean factory

### setDefaultBeanFactory

    public static void setDefaultBeanFactory(BeanFactory factory)

  Sets the default bean factory. This factory will be used for all create operations, for which no special factory is provided in the bean declaration.

  Parameters:
    `factory` - the default bean factory (must not be null)

### initBean

    public static void initBean(Object bean,
                                BeanDeclaration data)
                         throws ConfigurationRuntimeException

  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)
                                   throws ConfigurationRuntimeException

  Initializes the beans properties.

  Parameters:
    `bean` - the bean to be initialized
    `data` - the bean declaration
  Throws:
    `ConfigurationRuntimeException` - if a property cannot be set

### 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 static Object createBean(BeanDeclaration data,
                                    Class<?> defaultClass,
                                    Object param)
                             throws ConfigurationRuntimeException

  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 static Object createBean(BeanDeclaration data,
                                    Class<?> defaultClass)
                             throws ConfigurationRuntimeException

  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 static Object createBean(BeanDeclaration data)
                             throws ConfigurationRuntimeException

  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

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