org.apache.commons.beanutils
Class LazyDynaClass

java.lang.Object
  |
  +--org.apache.commons.beanutils.BasicDynaClass
        |
        +--org.apache.commons.beanutils.LazyDynaClass
All Implemented Interfaces:
DynaClass, MutableDynaClass, java.io.Serializable

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.

Author:
Niall Pemberton
See Also:
LazyDynaBean, Serialized Form

Field Summary
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
LazyDynaClass()
          Construct a new LazyDynaClass with default parameters.
LazyDynaClass(java.lang.String name)
          Construct a new LazyDynaClass with the specified name.
LazyDynaClass(java.lang.String name, java.lang.Class dynaBeanClass)
          Construct a new LazyDynaClass with the specified name and DynaBean class.
LazyDynaClass(java.lang.String name, java.lang.Class dynaBeanClass, DynaProperty[] properties)
          Construct a new LazyDynaClass with the specified name, DynaBean class and properties.
LazyDynaClass(java.lang.String name, DynaProperty[] properties)
          Construct a new LazyDynaClass with the specified name and properties.
 
Method Summary
protected  void add(DynaProperty property)
          Add a new dynamic property.
 void add(java.lang.String name)
          Add a new dynamic property with no restrictions on data type, readability, or writeability.
 void add(java.lang.String name, java.lang.Class type)
          Add a new dynamic property with the specified data type, but with no restrictions on readability or writeability.
 void add(java.lang.String name, java.lang.Class type, boolean readable, boolean writeable)
          Add a new dynamic property with the specified data type, readability, and writeability.
 DynaProperty getDynaProperty(java.lang.String name)
          Return a property descriptor for the specified property.
 boolean isDynaProperty(java.lang.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(java.lang.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(java.lang.String name)
Construct a new LazyDynaClass with the specified name.

Parameters:
name - Name of this DynaBean class

LazyDynaClass

public LazyDynaClass(java.lang.String name,
                     java.lang.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(java.lang.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(java.lang.String name,
                     java.lang.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 intances
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

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 - The new restricted state

isReturnNull

public boolean isReturnNull()
Should this DynaClass return a null from the getDynaProperty(name) method if the property doesn't exist.


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.


add

public void add(java.lang.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:
java.lang.IllegalArgumentException - if name is null
java.lang.IllegalStateException - if this DynaClass is currently restricted, so no new properties can be added

add

public void add(java.lang.String name,
                java.lang.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:
java.lang.IllegalArgumentException - if name is null
java.lang.IllegalStateException - if this DynaClass is currently restricted, so no new properties can be added

add

public void add(java.lang.String name,
                java.lang.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:
java.lang.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:
java.lang.IllegalArgumentException - if name is null
java.lang.IllegalStateException - if this DynaClass is currently restricted, so no new properties can be added

remove

public void remove(java.lang.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:
java.lang.IllegalArgumentException - if name is null
java.lang.IllegalStateException - if this DynaClass is currently restricted, so no properties can be removed

getDynaProperty

public DynaProperty getDynaProperty(java.lang.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
Throws:
java.lang.IllegalArgumentException - if no property name is specified

isDynaProperty

public boolean isDynaProperty(java.lang.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).

Throws:
java.lang.IllegalArgumentException - if no property name is specified


Copyright (c) 2001-2004 - Apache Software Foundation