org.apache.velocity.context

Class AbstractContext

public abstract class AbstractContext extends InternalContextBase implements Context, Serializable

This class is the abstract base class for all conventional Velocity Context implementations. Simply extend this class and implement the abstract routines that access your preferred storage method. Takes care of context chaining. Also handles / enforces policy on null keys and values : The default implementation of this for application use is org.apache.velocity.VelocityContext. All thanks to Fedor for the chaining idea.

Version: $Id: AbstractContext.java,v 1.8.8.1 2004/03/03 23:22:54 geirm Exp $

Author: Geir Magnusson Jr. Fedor Karpelevitch Jason van Zyl

Field Summary
ContextinnerContext
the chained Context if any
Constructor Summary
AbstractContext()
default CTOR
AbstractContext(Context inner)
Chaining constructor accepts a Context argument.
Method Summary
booleancontainsKey(Object key)
Indicates whether the specified key is in the context.
Objectget(String key)
Gets the value corresponding to the provided key from the context.
ContextgetChainedContext()
returns innerContext if one is chained
Object[]getKeys()
Get all the keys for the values in the context
abstract booleaninternalContainsKey(Object key)
Implement to determine if a key is in the storage.
abstract ObjectinternalGet(String key)
Implement to return a value from the context storage.
abstract Object[]internalGetKeys()
Implement to return an object array of key strings from your storage.
abstract ObjectinternalPut(String key, Object value)
Implement to put a value into the context storage.
abstract ObjectinternalRemove(Object key)
I mplement to remove an item from your storage.
Objectput(String key, Object value)
Adds a name/value pair to the context.
Objectremove(Object key)
Removes the value associated with the specified key from the context.

Field Detail

innerContext

private Context innerContext
the chained Context if any

Constructor Detail

AbstractContext

public AbstractContext()
default CTOR

AbstractContext

public AbstractContext(Context inner)
Chaining constructor accepts a Context argument. It will relay get() operations into this Context in the even the 'local' get() returns null.

Parameters: inner context to be chained

Method Detail

containsKey

public boolean containsKey(Object key)
Indicates whether the specified key is in the context. Provided for debugging purposes.

Parameters: key The key to look for.

Returns: true if the key is in the context, false if not.

get

public Object get(String key)
Gets the value corresponding to the provided key from the context. Supports the chaining context mechanism. If the 'local' context doesn't have the value, we try to get it from the chained context.

Parameters: key The name of the desired value.

Returns: The value corresponding to the provided key or null if the key param is null.

getChainedContext

public Context getChainedContext()
returns innerContext if one is chained

Returns: Context if chained, null if not

getKeys

public Object[] getKeys()
Get all the keys for the values in the context

Returns: Object[] of keys in the Context. Does not return keys in chained context.

internalContainsKey

public abstract boolean internalContainsKey(Object key)
Implement to determine if a key is in the storage.

Currently, this method is not used internally by the Velocity core.

Parameters: key key to test for existance

Returns: true if found, false if not

internalGet

public abstract Object internalGet(String key)
Implement to return a value from the context storage.

The implementation of this method is required for proper operation of a Context implementation in general Velocity use.

Parameters: key key whose associated value is to be returned

Returns: object stored in the context

internalGetKeys

public abstract Object[] internalGetKeys()
Implement to return an object array of key strings from your storage.

Currently, this method is not used internally by the Velocity core.

Returns: array of keys

internalPut

public abstract Object internalPut(String key, Object value)
Implement to put a value into the context storage.

The implementation of this method is required for proper operation of a Context implementation in general Velocity use.

Parameters: key key with which to associate the value value value to be associated with the key

Returns: previously stored value if exists, or null

internalRemove

public abstract Object internalRemove(Object key)
I mplement to remove an item from your storage.

Currently, this method is not used internally by the Velocity core.

Parameters: key key to remove

Returns: object removed if exists, else null

put

public Object put(String key, Object value)
Adds a name/value pair to the context.

Parameters: key The name to key the provided value with. value The corresponding value.

Returns: Object that was replaced in the the Context if applicable or null if not.

remove

public Object remove(Object key)
Removes the value associated with the specified key from the context.

Parameters: key The name of the value to remove.

Returns: The value that the key was mapped to, or null if unmapped.

Copyright B) 2002 Apache Software Foundation. All Rights Reserved.