org.apache.commons.beanutils

## Class LazyDynaClass

- java.lang.Object
- - org.apache.commons.beanutils.BasicDynaClass
  - - org.apache.commons.beanutils.LazyDynaClass

- All Implemented Interfaces:
    Serializable, DynaClass, MutableDynaClass

      public class LazyDynaClass
      extends BasicDynaClass
      implements MutableDynaClass

  DynaClass which implements the `MutableDynaClass` interface.

  A `MutableDynaClass` is a specialized extension to `DynaClass` that allows properties to be added or removed dynamically.

  This implementation has one slightly unusual default behaviour - calling the `getDynaProperty(name)` method for a property which doesn't exist returns a `DynaProperty` rather than `null`. The reason for this is that `BeanUtils` calls this method to check if a property exists before trying to set the value. This would defeat the object of the `LazyDynaBean` which automatically adds missing properties when any of its `set()` methods are called. For this reason the `isDynaProperty(name)` method has been added to this implementation in order to determine if a property actually exists. If the more normal behaviour of returning `null` is required, then this can be achieved by calling the `setReturnNull(true)`.

  The `add(name, type, readable, writable)` method is not implemented and always throws an `UnsupportedOperationException`. I believe this attributes need to be added to the `DynaProperty` class in order to control read/write facilities.

  Version:
    $Id$
  See Also:
    `LazyDynaBean`, Serialized Form

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected boolean` | `restricted` Controls whether changes to this DynaClass's properties are allowed.
    `protected boolean` | `returnNull` Controls whether the `getDynaProperty()` method returns null if a property doesn't exist - or creates a new one.

    - ### Fields inherited from class org.apache.commons.beanutils.BasicDynaClass

      `constructor, constructorTypes, constructorValues, dynaBeanClass, name, properties, propertiesMap`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `LazyDynaClass()` Construct a new LazyDynaClass with default parameters.
    `LazyDynaClass(String name)` Construct a new LazyDynaClass with the specified name.
    `LazyDynaClass(String name, Class<?> dynaBeanClass)` Construct a new LazyDynaClass with the specified name and DynaBean class.
    `LazyDynaClass(String name, Class<?> dynaBeanClass, DynaProperty[] properties)` Construct a new LazyDynaClass with the specified name, DynaBean class and properties.
    `LazyDynaClass(String name, DynaProperty[] properties)` Construct a new LazyDynaClass with the specified name and properties.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `add(DynaProperty property)` Add a new dynamic property.
    `void` | `add(String name)` Add a new dynamic property with no restrictions on data type, readability, or writeability.
    `void` | `add(String name, Class<?> type)` Add a new dynamic property with the specified data type, but with no restrictions on readability or writeability.
    `void` | `add(String name, Class<?> type, boolean readable, boolean writeable)` Add a new dynamic property with the specified data type, readability, and writeability.
    `DynaProperty` | `getDynaProperty(String name)` Return a property descriptor for the specified property.
    `boolean` | `isDynaProperty(String name)` Indicate whether a property actually exists.
    `boolean` | `isRestricted()` Is this DynaClass currently restricted.
    `boolean` | `isReturnNull()` Should this DynaClass return a `null` from the `getDynaProperty(name)` method if the property doesn't exist.
    `void` | `remove(String name)` Remove the specified dynamic property, and any associated data type, readability, and writeability, from this dynamic class.
    `void` | `setRestricted(boolean restricted)` Set whether this DynaClass is currently restricted.
    `void` | `setReturnNull(boolean returnNull)` Set whether this DynaClass should return a `null` from the `getDynaProperty(name)` method if the property doesn't exist.

    - ### Methods inherited from class org.apache.commons.beanutils.BasicDynaClass

      `getDynaBeanClass, getDynaProperties, getName, newInstance, setDynaBeanClass, setProperties`

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

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

    - ### Methods inherited from interface org.apache.commons.beanutils.DynaClass

      `getDynaProperties, getName, newInstance`

- - ### Field Detail

    - #### restricted

          protected boolean restricted

      Controls whether changes to this DynaClass's properties are allowed.

    - #### returnNull

          protected boolean returnNull

      Controls whether the `getDynaProperty()` method returns null if a property doesn't exist - or creates a new one.

      Default is `false`.

  - ### Constructor Detail

    - #### LazyDynaClass

          public LazyDynaClass()

      Construct a new LazyDynaClass with default parameters.

    - #### LazyDynaClass

          public LazyDynaClass(String name)

      Construct a new LazyDynaClass with the specified name.
      Parameters:
        `name` - Name of this DynaBean class

    - #### LazyDynaClass

          public LazyDynaClass(String name,
                               Class<?> dynaBeanClass)

      Construct a new LazyDynaClass with the specified name and DynaBean class.
      Parameters:
        `name` - Name of this DynaBean class
        `dynaBeanClass` - The implementation class for new instances

    - #### LazyDynaClass

          public LazyDynaClass(String name,
                               DynaProperty[] properties)

      Construct a new LazyDynaClass with the specified name and properties.
      Parameters:
        `name` - Name of this DynaBean class
        `properties` - Property descriptors for the supported properties

    - #### LazyDynaClass

          public LazyDynaClass(String name,
                               Class<?> dynaBeanClass,
                               DynaProperty[] properties)

      Construct a new LazyDynaClass with the specified name, DynaBean class and properties.
      Parameters:
        `name` - Name of this DynaBean class
        `dynaBeanClass` - The implementation class for new instances
        `properties` - Property descriptors for the supported properties

  - ### Method Detail

    - #### isRestricted

          public boolean isRestricted()

      Is this DynaClass currently restricted.

      If restricted, no changes to the existing registration of property names, data types, readability, or writeability are allowed.

      Specified by:
        `isRestricted` in interface `MutableDynaClass`
      Returns:
        `true` if this `MutableDynaClass` cannot be changed otherwise `false`

    - #### setRestricted

          public void setRestricted(boolean restricted)

      Set whether this DynaClass is currently restricted.

      If restricted, no changes to the existing registration of property names, data types, readability, or writeability are allowed.

      Specified by:
        `setRestricted` in interface `MutableDynaClass`
      Parameters:
        `restricted` - `true` if this `MutableDynaClass` cannot be changed otherwise `false`

    - #### isReturnNull

          public boolean isReturnNull()

      Should this DynaClass return a `null` from the `getDynaProperty(name)` method if the property doesn't exist.
      Returns:
        `true` if a `null` `DynaProperty` should be returned if the property doesn't exist, otherwise `false` if a new `DynaProperty` should be created.

    - #### setReturnNull

          public void setReturnNull(boolean returnNull)

      Set whether this DynaClass should return a `null` from the `getDynaProperty(name)` method if the property doesn't exist.
      Parameters:
        `returnNull` - `true` if a `null` `DynaProperty` should be returned if the property doesn't exist, otherwise `false` if a new `DynaProperty` should be created.

    - #### add

          public void add(String name)

      Add a new dynamic property with no restrictions on data type, readability, or writeability.
      Specified by:
        `add` in interface `MutableDynaClass`
      Parameters:
        `name` - Name of the new dynamic property
      Throws:
        `IllegalArgumentException` - if name is null
        `IllegalStateException` - if this DynaClass is currently restricted, so no new properties can be added

    - #### add

          public void add(String name,
                          Class<?> type)

      Add a new dynamic property with the specified data type, but with no restrictions on readability or writeability.
      Specified by:
        `add` in interface `MutableDynaClass`
      Parameters:
        `name` - Name of the new dynamic property
        `type` - Data type of the new dynamic property (null for no restrictions)
      Throws:
        `IllegalArgumentException` - if name is null
        `IllegalStateException` - if this DynaClass is currently restricted, so no new properties can be added

    - #### add

          public void add(String name,
                          Class<?> type,
                          boolean readable,
                          boolean writeable)

      Add a new dynamic property with the specified data type, readability, and writeability.

      N.B.Support for readable/writeable properties has not been implemented and this method always throws a `UnsupportedOperationException`.

      I'm not sure the intention of the original authors for this method, but it seems to me that readable/writable should be attributes of the `DynaProperty` class (which they are not) and is the reason this method has not been implemented.

      Specified by:
        `add` in interface `MutableDynaClass`
      Parameters:
        `name` - Name of the new dynamic property
        `type` - Data type of the new dynamic property (null for no restrictions)
        `readable` - Set to `true` if this property value should be readable
        `writeable` - Set to `true` if this property value should be writeable
      Throws:
        `UnsupportedOperationException` - anytime this method is called

    - #### add

          protected void add(DynaProperty property)

      Add a new dynamic property.
      Parameters:
        `property` - Property the new dynamic property to add.
      Throws:
        `IllegalArgumentException` - if name is null
        `IllegalStateException` - if this DynaClass is currently restricted, so no new properties can be added

    - #### remove

          public void remove(String name)

      Remove the specified dynamic property, and any associated data type, readability, and writeability, from this dynamic class. NOTE - This does NOT cause any corresponding property values to be removed from DynaBean instances associated with this DynaClass.
      Specified by:
        `remove` in interface `MutableDynaClass`
      Parameters:
        `name` - Name of the dynamic property to remove
      Throws:
        `IllegalArgumentException` - if name is null
        `IllegalStateException` - if this DynaClass is currently restricted, so no properties can be removed

    - #### getDynaProperty

          public DynaProperty getDynaProperty(String name)

      Return a property descriptor for the specified property.

      If the property is not found and the `returnNull` indicator is `true`, this method always returns `null`.

      If the property is not found and the `returnNull` indicator is `false` a new property descriptor is created and returned (although its not actually added to the DynaClass's properties). This is the default beahviour.

      The reason for not returning a `null` property descriptor is that `BeanUtils` uses this method to check if a property exists before trying to set it - since these Lazy implementations automatically add any new properties when they are set, returning `null` from this method would defeat their purpose.

      Specified by:
        `getDynaProperty` in interface `DynaClass`
      Overrides:
        `getDynaProperty` in class `BasicDynaClass`
      Parameters:
        `name` - Name of the dynamic property for which a descriptor is requested
      Returns:
        The dyna property for the specified name
      Throws:
        `IllegalArgumentException` - if no property name is specified

    - #### isDynaProperty

          public boolean isDynaProperty(String name)

      Indicate whether a property actually exists.

      N.B. Using `getDynaProperty(name) == null` doesn't work in this implementation because that method might return a DynaProperty if it doesn't exist (depending on the `returnNull` indicator).

      Parameters:
        `name` - The name of the property to check
      Returns:
        `true` if there is a property of the specified name, otherwise `false`
      Throws:
        `IllegalArgumentException` - if no property name is specified

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