org.codehaus.plexus.context

Class DefaultContext

public class DefaultContext extends Object implements Context

Default implementation of Context. This implementation is a static hierarchial store. It has the normal get() and put methods. The hide method will hide a property. When a property has been hidden the context will not search in the parent context for the value.

Version: $Id: DefaultContext.java 1323 2004-12-20 23:00:59Z jvanzyl $

Author: Avalon Development Team

Nested Class Summary
static class	DefaultContext.Hidden This class is only used as a marker in the map to indicate a hidden value.

Field Summary
Map	contextData Context data.
static DefaultContext.Hidden	HIDDEN_MAKER
Context	parent Parent Context.
boolean	readOnly Is the context read only.

Constructor Summary
	DefaultContext(Map contextData, Context parent) Create a Context with specified data and parent.
	DefaultContext(Map contextData) Create a empty Context with specified data.
	DefaultContext(Context parent) Create a Context with specified parent.
	DefaultContext() Create a empty Context with no parent.

Method Summary
protected void	checkWriteable() Utility method to check if context is writeable and if not throw exception.
boolean	contains(Object key) Returns true if the map or the parent map contains the key.
Object	get(Object key) Returns the value of the key.
protected Map	getContextData() Utility method to retrieve context data.
protected Context	getParent() Get parent context if any.
void	hide(Object key) Hides the item in the context.
void	makeReadOnly() Make the context read-only.
void	put(Object key, Object value) Helper method for adding items to Context.

Field Detail

contextData

private Map contextData

Context data.

HIDDEN_MAKER

private static DefaultContext.Hidden HIDDEN_MAKER

parent

private Context parent

Parent Context.

readOnly

private boolean readOnly

Is the context read only.

Constructor Detail

DefaultContext

public DefaultContext(Map contextData, Context parent)

Create a Context with specified data and parent.

Parameters: contextData the context data parent the parent Context (may be null)

DefaultContext

public DefaultContext(Map contextData)

Create a empty Context with specified data.

Parameters: contextData the context data

DefaultContext

public DefaultContext(Context parent)

Create a Context with specified parent.

Parameters: parent the parent Context (may be null)

DefaultContext

public DefaultContext()

Create a empty Context with no parent.

Method Detail

checkWriteable

protected void checkWriteable()

Utility method to check if context is writeable and if not throw exception.

Throws: java.lang.IllegalStateException if context is read only

contains

public boolean contains(Object key)

Returns true if the map or the parent map contains the key.

Parameters: key The key to search for.

Returns: Returns true if the key was found.

get

public Object get(Object key)

Returns the value of the key. If the key can't be found it will throw a exception.

Parameters: key The key of the value to look up.

Returns: Returns

Throws: ContextException If the key doesn't exist.

getContextData

protected Map getContextData()

Utility method to retrieve context data.

Returns: the context data

getParent

protected Context getParent()

Get parent context if any.

Returns: the parent Context (may be null)

hide

public void hide(Object key)

Hides the item in the context. After remove(key) has been called, a get(key) will always fail, even if the parent context has such a mapping.

Parameters: key the items key

Throws: java.lang.IllegalStateException if context is read only

makeReadOnly

public void makeReadOnly()

Make the context read-only. Any attempt to write to the context via put() will result in an IllegalStateException.

put

public void put(Object key, Object value)

Helper method for adding items to Context.

Parameters: key the items key value the item

Throws: java.lang.IllegalStateException if context is read only