org.apache.commons.chain.impl
Class ContextBase

java.lang.Object
  java.util.AbstractMap<K,V>
      java.util.HashMap
          org.apache.commons.chain.impl.ContextBase

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map, Context

Direct Known Subclasses:

WebContext

public class ContextBase
extends java.util.HashMap
implements Context

Convenience base class for Context implementations.

In addition to the minimal functionality required by the Context interface, this class implements the recommended support for Attribute-Property Transparency. This is implemented by analyzing the available JavaBeans properties of this class (or its subclass), exposes them as key-value pairs in the Map, with the key being the name of the property itself.

IMPLEMENTATION NOTE - Because empty is a read-only property defined by the Map interface, it may not be utilized as an attribute key or property name.

Version:

$Revision: 499247 $ $Date: 2007-01-24 04:09:44 +0000 (Wed, 24 Jan 2007) $

Author:

Craig R. McClanahan

See Also:

Serialized Form

Nested Class Summary

private class	ContextBase.EntrySetImpl Private implementation of Set that implements the semantics required for the value returned by entrySet().
private class	ContextBase.EntrySetIterator Private implementation of Iterator for the Set returned by entrySet().
private class	ContextBase.MapEntryImpl Private implementation of Map.Entry for each item in EntrySetImpl.
private class	ContextBase.ValuesImpl Private implementation of Collection that implements the semantics required for the value returned by values().
private class	ContextBase.ValuesIterator Private implementation of Iterator for the Collection returned by values().

Nested classes/interfaces inherited from class java.util.AbstractMap

java.util.AbstractMap.SimpleEntry<K,V>, java.util.AbstractMap.SimpleImmutableEntry<K,V>

Nested classes/interfaces inherited from interface java.util.Map

java.util.Map.Entry<K,V>

Field Summary

private java.util.Map	descriptors The PropertyDescriptors for all JavaBeans properties of this Context implementation class, keyed by property name.
private java.beans.PropertyDescriptor[]	pd The same PropertyDescriptors as an array.
private static java.lang.Object	singleton Distinguished singleton value that is stored in the map for each key that is actually a property.
private static java.lang.Object[]	zeroParams Zero-length array of parameter values for calling property getters.

Constructor Summary

ContextBase()
Default, no argument constructor.

ContextBase(java.util.Map map)
Initialize the contents of this Context by copying the values from the specified Map.

Method Summary

void	clear() Override the default Map behavior to clear all keys and values except those corresponding to JavaBeans properties.
boolean	containsValue(java.lang.Object value) Override the default Map behavior to return true if the specified value is present in either the underlying Map or one of the local property values.
private java.util.Iterator	entriesIterator() Return an Iterator over the set of Map.Entry objects representing our key-value pairs.
private java.util.Map.Entry	entry(java.lang.Object key) Return a Map.Entry for the specified key value, if it is present; otherwise, return null.
java.util.Set	entrySet() Override the default Map behavior to return a Set that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.
java.lang.Object	get(java.lang.Object key) Override the default Map behavior to return the value of a local property if the specified key matches a local property name.
private void	initialize() Customize the contents of our underlying Map so that it contains keys corresponding to all of the JavaBeans properties of the Context implementation class.
boolean	isEmpty() Override the default Map behavior to return true if the underlying Map only contains key-value pairs for local properties (if any).
java.util.Set	keySet() Override the default Map behavior to return a Set that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.
java.lang.Object	put(java.lang.Object key, java.lang.Object value) Override the default Map behavior to set the value of a local property if the specified key matches a local property name.
void	putAll(java.util.Map map) Override the default Map behavior to call the put() method individually for each key-value pair in the specified Map.
private java.lang.Object	readProperty(java.beans.PropertyDescriptor descriptor) Get and return the value for the specified property.
private boolean	remove(java.util.Map.Entry entry) Remove the specified key-value pair, if it exists, and return true.
java.lang.Object	remove(java.lang.Object key) Override the default Map behavior to throw UnsupportedOperationException on any attempt to remove a key that is the name of a local property.
java.util.Collection	values() Override the default Map behavior to return a Collection that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.
private java.util.Iterator	valuesIterator() Return an Iterator over the set of values in this Map.
private void	writeProperty(java.beans.PropertyDescriptor descriptor, java.lang.Object value) Set the value for the specified property.

Methods inherited from class java.util.HashMap

clone, containsKey, size

Methods inherited from class java.util.AbstractMap

equals, hashCode, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Map

containsKey, equals, hashCode, size

Field Detail

descriptors

private transient java.util.Map descriptors

The PropertyDescriptors for all JavaBeans properties of this Context implementation class, keyed by property name. This collection is allocated only if there are any JavaBeans properties.

pd

private transient java.beans.PropertyDescriptor[] pd

The same PropertyDescriptors as an array.

singleton

private static java.lang.Object singleton

Distinguished singleton value that is stored in the map for each key that is actually a property. This value is used to ensure that equals() comparisons will always fail.

zeroParams

private static java.lang.Object[] zeroParams

Zero-length array of parameter values for calling property getters.

Constructor Detail

ContextBase

public ContextBase()

Default, no argument constructor.

ContextBase

public ContextBase(java.util.Map map)

Initialize the contents of this Context by copying the values from the specified Map. Any keys in map that correspond to local properties will cause the setter method for that property to be called.

Parameters:

map - Map whose key-value pairs are added

Throws:

java.lang.IllegalArgumentException - if an exception is thrown writing a local property value

java.lang.UnsupportedOperationException - if a local property does not have a write method.

Method Detail

clear

public void clear()

Override the default Map behavior to clear all keys and values except those corresponding to JavaBeans properties.

Specified by:

clear in interface java.util.Map

Overrides:

clear in class java.util.HashMap

containsValue

public boolean containsValue(java.lang.Object value)

Override the default Map behavior to return true if the specified value is present in either the underlying Map or one of the local property values.

Specified by:

containsValue in interface java.util.Map

Overrides:

containsValue in class java.util.HashMap

Parameters:

value - the value look for in the context.

Returns:

true if found in this context otherwise false.

Throws:

java.lang.IllegalArgumentException - if a property getter throws an exception

entrySet

public java.util.Set entrySet()

Override the default Map behavior to return a Set that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.

Specified by:

entrySet in interface java.util.Map

Overrides:

entrySet in class java.util.HashMap

Returns:

Set of entries in the Context.

get

public java.lang.Object get(java.lang.Object key)

Override the default Map behavior to return the value of a local property if the specified key matches a local property name.

IMPLEMENTATION NOTE - If the specified key identifies a write-only property, null will arbitrarily be returned, in order to avoid difficulties implementing the contracts of the Map interface.

Specified by:

get in interface java.util.Map

Overrides:

get in class java.util.HashMap

Parameters:

key - Key of the value to be returned

Returns:

The value for the specified key.

Throws:

java.lang.IllegalArgumentException - if an exception is thrown reading this local property value

java.lang.UnsupportedOperationException - if this local property does not have a read method.

isEmpty

public boolean isEmpty()

Override the default Map behavior to return true if the underlying Map only contains key-value pairs for local properties (if any).

Specified by:

isEmpty in interface java.util.Map

Overrides:

isEmpty in class java.util.HashMap

Returns:

true if this Context is empty, otherwise false.

keySet

public java.util.Set keySet()

Override the default Map behavior to return a Set that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.

Specified by:

keySet in interface java.util.Map

Overrides:

keySet in class java.util.HashMap

Returns:

The set of keys for objects in this Context.

put

public java.lang.Object put(java.lang.Object key,
                            java.lang.Object value)

Override the default Map behavior to set the value of a local property if the specified key matches a local property name.

Specified by:

put in interface java.util.Map

Overrides:

put in class java.util.HashMap

Parameters:

key - Key of the value to be stored or replaced

value - New value to be stored

Returns:

The value added to the Context.

Throws:

java.lang.IllegalArgumentException - if an exception is thrown reading or wrting this local property value

java.lang.UnsupportedOperationException - if this local property does not have both a read method and a write method

putAll

public void putAll(java.util.Map map)

Override the default Map behavior to call the put() method individually for each key-value pair in the specified Map.

Specified by:

putAll in interface java.util.Map

Overrides:

putAll in class java.util.HashMap

Parameters:

map - Map containing key-value pairs to store (or replace)

Throws:

java.lang.IllegalArgumentException - if an exception is thrown reading or wrting a local property value

java.lang.UnsupportedOperationException - if a local property does not have both a read method and a write method

remove

public java.lang.Object remove(java.lang.Object key)

Override the default Map behavior to throw UnsupportedOperationException on any attempt to remove a key that is the name of a local property.

Specified by:

remove in interface java.util.Map

Overrides:

remove in class java.util.HashMap

Parameters:

key - Key to be removed

Returns:

The value removed from the Context.

Throws:

java.lang.UnsupportedOperationException - if the specified key matches the name of a local property

values

public java.util.Collection values()

Override the default Map behavior to return a Collection that meets the specified default behavior except for attempts to remove the key for a property of the Context implementation class, which will throw UnsupportedOperationException.

Specified by:

values in interface java.util.Map

Overrides:

values in class java.util.HashMap

Returns:

The collection of values in this Context.

entriesIterator

private java.util.Iterator entriesIterator()

Return an Iterator over the set of Map.Entry objects representing our key-value pairs.

entry

private java.util.Map.Entry entry(java.lang.Object key)

Return a Map.Entry for the specified key value, if it is present; otherwise, return null.

Parameters:

key - Attribute key or property name

initialize

private void initialize()

Customize the contents of our underlying Map so that it contains keys corresponding to all of the JavaBeans properties of the Context implementation class.

Throws:

java.lang.IllegalArgumentException - if an exception is thrown writing this local property value

java.lang.UnsupportedOperationException - if this local property does not have a write method.

readProperty

private java.lang.Object readProperty(java.beans.PropertyDescriptor descriptor)

Get and return the value for the specified property.

Parameters:

descriptor - PropertyDescriptor for the specified property

Throws:

java.lang.IllegalArgumentException - if an exception is thrown reading this local property value

java.lang.UnsupportedOperationException - if this local property does not have a read method.

remove

private boolean remove(java.util.Map.Entry entry)

Remove the specified key-value pair, if it exists, and return true. If this pair does not exist, return false.

Parameters:

entry - Key-value pair to be removed

Throws:

java.lang.UnsupportedOperationException - if the specified key identifies a property instead of an attribute

valuesIterator

private java.util.Iterator valuesIterator()

Return an Iterator over the set of values in this Map.

writeProperty

private void writeProperty(java.beans.PropertyDescriptor descriptor,
                           java.lang.Object value)

Set the value for the specified property.

Parameters:

descriptor - PropertyDescriptor for the specified property

value - The new value for this property (must be of the correct type)

Throws:

java.lang.IllegalArgumentException - if an exception is thrown writing this local property value

java.lang.UnsupportedOperationException - if this local property does not have a write method.