/******************************************************************************* * Copyright (c) 2000, 2004 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.core.expressions; import org.eclipse.core.runtime.CoreException; /** * An evaluation context is used to manage a set of objects needed during * XML expression evaluation. A context has a parent context, can manage * a set of named variables and has a default variable. The default variable * is used during XML expression evaluation if no explicit variable is * referenced. *
* This interface is not intended to be implemented by clients. Clients
* are allowed to instantiate EvaluationContext
.
*
null
if
* this is the root of the evaluation context hierarchy.
*
* @return the parent evaluation context or null
*/
public IEvaluationContext getParent();
/**
* Returns the root evaluation context.
*
* @return the root evaluation context
*/
public IEvaluationContext getRoot();
/**
* Specifies whether this evaluation context allows activation
* of plug-ins for testers used in the expression tree. To actual
* trigger the plug-in loading this flag has to be set to
* true
and the actual test expression must have the
* attribute forcePluginActivation
set to
* true
as well.
*
* @param value whether this evaluation context allows plug-in
* activation
*/
public void setAllowPluginActivation(boolean value);
/**
* Returns whether this evaluation context supports plug-in
* activation.
*
* @return whether plug-in activation is supported or not
*/
public boolean getAllowPluginActivation();
/**
* Returns the default variable.
*
* @return the default variable or null
if
* no default variable is managed.
*/
public Object getDefaultVariable();
/**
* Adds a new named variable to this context. If a variable
* with the name already exists the new one overrides the
* existing one.
*
* @param name the variable's name
* @param value the variable's value
*/
public void addVariable(String name, Object value);
/**
* Removes the variable managed under the given name
* from this evaluation context.
*
* @param name the variable's name
* @return the currently stored value or null
if
* the variable doesn't exist
*/
public Object removeVariable(String name);
/**
* Returns the variable managed under the given name.
*
* @param name the variable's name
* @return the variable's value or null
if the content
* doesn't manage a variable with the given name
*/
public Object getVariable(String name);
/**
* Resolves a variable for the given name and arguments. This
* method can be used to dynamically resolve variable such as
* plug-in descriptors, resources, etc. The method is used
* by the resolve
expression.
*
* @param name the variable to resolve
* @param args an object array of arguments used to resolve the
* variable
* @return the variable's value or null
if no variable
* can be resolved for the given name and arguments
* @exception CoreException if an errors occurs while resolving
* the variable
*/
public Object resolveVariable(String name, Object[] args) throws CoreException;
}