Package 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 Details

    • 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 Details

    • BeanHelper

      public BeanHelper()
      Constructs a new instance of BeanHelper with the default instance of DefaultBeanFactory as default BeanFactory.

    • BeanHelper

      public BeanHelper(BeanFactory defaultBeanFactory)
      Constructs a new instance of BeanHelper and sets the specified default BeanFactory.
      Parameters:
      defaultBeanFactory - the default BeanFactory (can be null, then a default instance is used)

  • Method Details

    • registerBeanFactory

      public void registerBeanFactory(String name, BeanFactory factory)
      Registers 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()
      Gets 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()
      Gets 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)
      Sets 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 writable 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)
      Creates 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)
      Creates 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