org.apache.velocity.context

Class AbstractContext

Implemented Interfaces:
Context, Serializable, InternalEventContext, InternalHousekeepingContext
Known Direct Subclasses:
VelocityContext

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 2001/10/22 03:53:23 jon Exp $

Authors:
Geir Magnusson Jr.
Fedor Karpelevitch
Jason van Zyl

Nested Class Summary

Field Summary

private Context
innerContext
the chained Context if any

Fields inherited from class org.apache.velocity.context.InternalContextBase

currentResource, eventCartridge, introspectionCache, templateNameStack

Constructor Summary

AbstractContext()
default CTOR
AbstractContext(Context inner)
Chaining constructor accepts a Context argument.

Method Summary

boolean
containsKey(Object key)
Indicates whether the specified key is in the context.
Object
get(String key)
Gets the value corresponding to the provided key from the context.
Context
getChainedContext()
returns innerContext if one is chained
Object[]
getKeys()
Get all the keys for the values in the context
boolean
internalContainsKey(Object key)
Implement to determine if a key is in the storage.
Object
internalGet(String key)
Implement to return a value from the context storage.
Object[]
internalGetKeys()
Implement to return an object array of key strings from your storage.
Object
internalPut(String key, Object value)
Implement to put a value into the context storage.
Object
internalRemove(Object key)
I mplement to remove an item from your storage.
Object
put(String key, Object value)
Adds a name/value pair to the context.
Object
remove(Object key)
Removes the value associated with the specified key from the context.

Methods inherited from class org.apache.velocity.context.InternalContextBase

attachEventCartridge, getCurrentResource, getCurrentTemplateName, getEventCartridge, getTemplateNameStack, icacheGet, icachePut, popCurrentTemplateName, pushCurrentTemplateName, setCurrentResource

Field Details

innerContext

private Context innerContext
the chained Context if any

Constructor Details

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 Details

containsKey

public boolean containsKey(Object key)
Indicates whether the specified key is in the context. Provided for debugging purposes.
Specified by:
containsKey in interface Context

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.
Specified by:
get in interface 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
Specified by:
getKeys in interface Context

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


internalContainsKey

public 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 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 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 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 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.
Specified by:
put in interface 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.
Specified by:
remove in interface Context

Parameters:
key - The name of the value to remove.

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


Copyright © 2003 Apache Software Foundation. All Rights Reserved.