org.apache.velocity.context
Class AbstractContext

java.lang.Object
  |
  +--org.apache.velocity.context.InternalContextBase
        |
        +--org.apache.velocity.context.AbstractContext
All Implemented Interfaces:
Context, InternalEventContext, InternalHousekeepingContext, java.io.Serializable
Direct Known Subclasses:
VelocityContext

public abstract class AbstractContext
extends InternalContextBase
implements Context, java.io.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 $
Author:
Geir Magnusson Jr., Fedor Karpelevitch, Jason van Zyl
See Also:
Serialized Form

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(java.lang.Object key)
          Indicates whether the specified key is in the context.
 java.lang.Object get(java.lang.String key)
          Gets the value corresponding to the provided key from the context.
 Context getChainedContext()
          returns innerContext if one is chained
 java.lang.Object[] getKeys()
          Get all the keys for the values in the context
abstract  boolean internalContainsKey(java.lang.Object key)
          Implement to determine if a key is in the storage.
abstract  java.lang.Object internalGet(java.lang.String key)
          Implement to return a value from the context storage.
abstract  java.lang.Object[] internalGetKeys()
          Implement to return an object array of key strings from your storage.
abstract  java.lang.Object internalPut(java.lang.String key, java.lang.Object value)
          Implement to put a value into the context storage.
abstract  java.lang.Object internalRemove(java.lang.Object key)
          I mplement to remove an item from your storage.
 java.lang.Object put(java.lang.String key, java.lang.Object value)
          Adds a name/value pair to the context.
 java.lang.Object remove(java.lang.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
 
Methods inherited from class java.lang.Object
, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait
 

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

internalGet

public abstract java.lang.Object internalGet(java.lang.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

internalPut

public abstract java.lang.Object internalPut(java.lang.String key,
                                             java.lang.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

internalContainsKey

public abstract boolean internalContainsKey(java.lang.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

internalGetKeys

public abstract java.lang.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

internalRemove

public abstract java.lang.Object internalRemove(java.lang.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 java.lang.Object put(java.lang.String key,
                            java.lang.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.

get

public java.lang.Object get(java.lang.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.

containsKey

public boolean containsKey(java.lang.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.

getKeys

public java.lang.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.

remove

public java.lang.Object remove(java.lang.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.

getChainedContext

public Context getChainedContext()
returns innerContext if one is chained
Returns:
Context if chained, null if not


Copyright © 2003 Apache Software Foundation. All Rights Reserved.