Package org.apache.commons.beanutils

# Class BeanToPropertyValueTransformer

java.lang.Object
org.apache.commons.beanutils.BeanToPropertyValueTransformer

All Implemented Interfaces:
  `org.apache.commons.collections.Transformer`

public class BeanToPropertyValueTransformer extends Object implements org.apache.commons.collections.Transformer

`Transformer` that outputs a property value.

An implementation of `org.apache.commons.collections.Transformer` that transforms the object provided by returning the value of a specified property of the object. The constructor for `BeanToPropertyValueTransformer` requires the name of the property that will be used in the transformation. The property can be a simple, nested, indexed, or mapped property as defined by `org.apache.commons.beanutils.PropertyUtils`. If any object in the property path specified by `propertyName` is `null` then the outcome is based on the value of the `ignoreNull` attribute.

A typical usage might look like:

     // create the transformer
     BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city" );

     // transform the Collection
     Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer );

This would take a `Collection` of person objects and return a `Collection` of objects which represents the cities in which each person lived. Assuming...

- The top level object in the `peeopleCollection` is an object which represents a person.
- The person object has a `getAddress()` method which returns an object which represents a person's address.
- The address object has a `getCity()` method which returns an object which represents the city in which a person lives.

See Also:
  - `PropertyUtils`
  - `Transformer`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `BeanToPropertyValueTransformer(String propertyName)`
  Constructs a Transformer which does not ignore nulls.
  `BeanToPropertyValueTransformer(String propertyName, boolean ignoreNull)`
  Constructs a Transformer and sets ignoreNull.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `String`
  `getPropertyName()`
  Returns the name of the property that will be used in the transformation of the bean.
  `boolean`
  `isIgnoreNull()`
  Returns the flag which determines whether `null` objects in the property path will genenerate an `IllegalArgumentException` or not.
  `Object`
  `transform(Object object)`
  Returns the value of the property named in the transformer's constructor for the object provided.

  ### Methods inherited from class java.lang.Object

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

- ## Constructor Details

  - ### BeanToPropertyValueTransformer

    public BeanToPropertyValueTransformer(String propertyName)
    Constructs a Transformer which does not ignore nulls. Constructor which takes the name of the property that will be used in the transformation and assumes `ignoreNull` to be `false`.
    Parameters:
      `propertyName` - The name of the property that will be used in the transformation.
    Throws:
      `IllegalArgumentException` - If the `propertyName` is `null` or empty.

  - ### BeanToPropertyValueTransformer

    public BeanToPropertyValueTransformer(String propertyName, boolean ignoreNull)
    Constructs a Transformer and sets ignoreNull. Constructor which takes the name of the property that will be used in the transformation and a boolean which determines whether `null` objects in the property path will genenerate an `IllegalArgumentException` or not.
    Parameters:
      `propertyName` - The name of the property that will be used in the transformation.
      `ignoreNull` - Determines whether `null` objects in the property path will genenerate an `IllegalArgumentException` or not.
    Throws:
      `IllegalArgumentException` - If the `propertyName` is `null` or empty.

- ## Method Details

  - ### getPropertyName

    public String getPropertyName()
    Returns the name of the property that will be used in the transformation of the bean.
    Returns:
      The name of the property that will be used in the transformation of the bean.

  - ### isIgnoreNull

    public boolean isIgnoreNull()
    Returns the flag which determines whether `null` objects in the property path will genenerate an `IllegalArgumentException` or not. If set to `true` then if any objects in the property path evaluate to `null` then the `IllegalArgumentException` throw by `PropertyUtils` will be logged but not rethrown and `null` will be returned. If set to `false` then if any objects in the property path evaluate to `null` then the `IllegalArgumentException` throw by `PropertyUtils` will be logged and rethrown.
    Returns:
      The flag which determines whether `null` objects in the property path will genenerate an `IllegalArgumentException` or not.

  - ### transform

    public Object transform(Object object)
    Returns the value of the property named in the transformer's constructor for the object provided. If any object in the property path leading up to the target property is `null` then the outcome will be based on the value of the `ignoreNull` attribute. By default, `ignoreNull` is `false` and would result in an `IllegalArgumentException` if an object in the property path leading up to the target property is `null`.
    Specified by:
      `transform` in interface `org.apache.commons.collections.Transformer`
    Parameters:
      `object` - The object to be transformed.
    Returns:
      The value of the property named in the transformer's constructor for the object provided.
    Throws:
      `IllegalArgumentException` - If an IllegalAccessException, InvocationTargetException, or NoSuchMethodException is thrown when trying to access the property specified on the object provided. Or if an object in the property path provided is `null` and `ignoreNull` is set to `false`.