/*******************************************************************************
* CogTool Copyright Notice and Distribution Terms
* CogTool 1.3, Copyright (c) 2005-2013 Carnegie Mellon University
* This software is distributed under the terms of the FSF Lesser
* Gnu Public License (see LGPL.txt).
*
* CogTool is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* CogTool is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
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* CogTool makes use of several third-party components, with the
* following notices:
*
* Eclipse SWT version 3.448
* Eclipse GEF Draw2D version 3.2.1
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*
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* ACT-R 6.0
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* Copyright (c) 1998-2007 Dan Bothell, Mike Byrne, Christian Lebiere &
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package edu.cmu.cs.hcii.cogtool.util;
import java.lang.reflect.Array;
import java.util.EventObject;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
/**
* Provides a mechanism for Attribute-Value behavior for properties on an
* object, i.e. properties that can be explicitly set to a particular value or
* set to use a "default value" as defined by an external authority.
*
* @see edu.cmu.cs.hcii.cogtool.util.Attributed
*/
public interface IAttributed extends IAlerter
{
/**
* Alert raised when setAuthority is invoked
*/
public static class AuthorityChange extends EventObject
{
/**
* The previous value of the authority
*/
public IAttributed oldAuthority;
public AuthorityChange(IAttributed attributed,
IAttributed prevAuthority)
{
super(attributed);
oldAuthority = prevAuthority;
}
}
/**
* Alert raised when setAttribute or unsetAttribute is invoked
*/
public static class AttributeChange extends EventObject
{
/**
* Set to true if setAttribute; false if unsetAttribute
*/
public boolean isSet;
/**
* Which attribute was set/unset
*/
public String attribute;
public AttributeChange(IAttributed attributed,
String attributeName,
boolean setting)
{
super(attributed);
attribute = attributeName;
isSet = setting;
}
}
/**
* Object to hold an attribute's definition (should be protected,
* but Java won't allow it).
*/
public static class AttributeDefinition<T>
{
public final String attrName;
public final Class<T> attrType;
public final T defaultValue;
public AttributeDefinition(String name, Class<T> type, T value)
{
if ((name == null) || (name.equals(""))) {
throw new IllegalArgumentException("Attribute name may not be null or empty");
}
if (type == null) {
throw new IllegalArgumentException("Attribute type may not be null");
}
this.attrName = name;
this.attrType = type;
this.defaultValue = value;
}
/**
* Default implementation for fetching the component type
* when the attribute value is an array. Used during the loading
* of attribute values when using ObjectSaver/ObjectLoader
* persistence support.
*
* Subclasses may override to support type evolution.
*/
protected Class<?> getArrayEltType()
{
return this.attrType.getComponentType();
}
/**
* Default implementation for fetching the aggregate value to
* hold the component values when loading attribute values using
* ObjectSaver/ObjectLoader persistence support.
*
* If the attribute value is not an array, the registered subclass
* instance must override this method to create and return the
* appropriate aggregate value (e.g., ArrayList(), HashMap(), etc.)
*/
public Object createAggregate(int count)
{
if (this.attrType.isArray()) {
return Array.newInstance(getArrayEltType(), count);
}
throw new IllegalStateException("Unknown aggregate type");
}
}
/**
* Global registry to hold attribute definitions
*/
public static class AttributeRegistry
{
public static AttributeRegistry ONLY = new AttributeRegistry();
// Maps name to AttributeDefinition
protected Map<String, AttributeDefinition<?>> attributeDefns =
new HashMap<String, AttributeDefinition<?>>();
protected AttributeRegistry() { }
public AttributeDefinition<?> getAttributeDefn(String attr)
{
return attributeDefns.get(attr);
}
/**
* Defines a new attribute and installs a default value. Call only
* once for each attribute type.
*
* @param attr a string identifier for the attribute to act upon
* @param type the value type allowed for this attribute
* @param value the default value for this attribute (could be null)
* @throws IllegalStateException if this attribute is already defined
* @throws IllegalArgumentException if attr == null, attr is empty,
* or type == null
*/
public <T> void defineAttribute(String attr,
Class<T> type,
T defaultValue)
{
AttributeDefinition<?> defn = getAttributeDefn(attr);
if (defn != null) {
throw new IllegalStateException("Cannot redefine attribute type: "
+ attr);
}
attributeDefns.put(attr,
new AttributeDefinition<T>(attr,
type,
defaultValue));
}
/**
* Method to register an attribute definition; generally,
* defineAttribute should be used; however, to support non-array
* aggregate attribute values (or array values that must "evolve"),
* registration must use an instance of an AttributeDefinition subclass.
*
* @param defn the instance of an AttributeDefinition subclass
* @throws IllegalStateException if this attribute is already defined
*/
public void registerAttribute(AttributeDefinition<?> defn)
{
AttributeDefinition<?> existingDefn =
getAttributeDefn(defn.attrName);
if (existingDefn != null) {
throw new IllegalStateException("Cannot redefine attribute type: "
+ defn.attrName);
}
attributeDefns.put(defn.attrName, defn);
}
/**
* Determine whether an attribute of the given name has been registered
* (that is, subsequent calls to getAttributeDefaultValue and
* getAttributeType will succeed.
*/
public boolean isDefined(String attr)
{
return attributeDefns.containsKey(attr);
}
/**
* Accessor for the stored value type of a named attribute.
*
* @param attr a string identifier for the attribute to act upon
* @return the Class of the value type for attr
* @throws IllegalStateException if the attribute is not defined
*/
public Class<?> getAttributeType(String attr)
{
AttributeDefinition<?> defn = getAttributeDefn(attr);
if (defn == null) {
throw new IllegalStateException("Undefined attribute type: "
+ attr);
}
return defn.attrType;
}
/**
* Accessor for the stored default value of a named attribute.
*
* @param attr a string identifier for the attribute to act upon
* @return the default value for attr
* @throws IllegalStateException if the attribute is not defined
*/
public Object getAttributeDefaultValue(String attr)
{
AttributeDefinition<?> defn = getAttributeDefn(attr);
if (defn == null) {
throw new IllegalStateException("Undefined attribute type: "
+ attr);
}
return defn.defaultValue;
}
/**
* Fetch the requested attribute value from the given IAttributed
* but, if it is <code>null</code>, then return the attribute's
* default value.
*/
public Object getAttribute(IAttributed attributed, String attrName)
{
if (attributed != null) {
return attributed.getAttribute(attrName);
}
return getAttributeDefaultValue(attrName);
}
}
/**
* Accesses the authority for the actual value of undefined attributes,
* i.e. the "parent" in the attribute-definition hierarchy. If this is an
* attribute hierarchy root, null is returned.
*
* @return the source of actual values of "default value" attributes
*/
public IAttributed getAuthority();
/**
* Mutates the authority for actual values of attributes not set locally.
* Ordinarily, this is set only once in the lifetime of an
* IAttributed, but it is possible to dynamically change the attribute-
* definition hierarchy at runtime. Note that changing the authority implies
* a possible change of value for all attributes currently using attributes
* undefined locally, which must be broadcast to all appropriate listeners.
*
* If the authority hierarchy does not provide a value, getAttribute will
* return the default value associated with the attribute.
*
* Raises an AuthorityChange alert.
*
* @param auth a source of actual values for "default value" attributes
*/
public void setAuthority(IAttributed auth);
/**
* Checks who in the authority hierarchy defines the given attribute.
* A return value of <code>null</code> indicates that a getAttribute
* would return the attribute type's default value. If the return value
* is equal to the receiver (i.e., <code>this</code>), then the value
* is defined "locally".
*
* @param attr a string identifier for the attribute to act upon
* @return the object in the authority hierarchy of the method receiver
* that defines a value for the given attribute; null if none
* @throws IllegalStateException if the attribute is not defined
*/
public IAttributed getDefiner(String attr);
/**
* Accessor for the value of the named attribute. This method always
* returns an "actual" value, which may be null.
*
* Note that the value returned here is by reference. Clients should code
* defensively to avoid unintended consequences.
*
* @param attr a string identifier for the attribute to act upon
* @return an actual stored value for the named attribute, which may be null
* @throws IllegalStateException if the attribute is not defined
*/
public Object getAttribute(String attr);
/**
* Determine if the value of the given attribute for the receiver
* is the default value.
*
* @param attr a string identifier for the attribute
* @return true if and only if the value returned is the same as
* the default value associated with the attribute
* @throws IllegalStateException if the attribute is not defined
*/
public boolean isAttributeDefault(String attr);
/**
* Mutator for the value of the named attribute.
* If the provided value does not match the value type defined for this
* attribute via the defineAttribute() method, an IllegalArgumentException
* will be thrown.
*
* Note that value is stored by reference. Clients should code defensively
* to avoid unintended consequences. Also note that the semantics of change
* notification for collections may vary between implementations due to
* performance concerns.
*
* Raises an AttributeChange alert.
*
* @param attr a string identifier for the attribute to act upon
* @param value the new value for the named attribute
* @throws IllegalStateException if the attribute is not defined
* @throws IllegalArgumentException iff the value type defined via
* defineAttribute(attr, ...) does not match the type of value
*/
public void setAttribute(String attr, Object value);
/**
* Because <code>null</code> is a valid attribute value, this method
* should be used to remove an attribute from being defined locally.
*
* Raises an AttributeChange alert.
*
* @param attr a string identifier for the attribute to act upon
* @throws IllegalStateException if the attribute is not defined
*/
public void unsetAttribute(String attr);
/**
* Enumerate the names of the attributes defined locally for this object.
*/
public Iterator<AttributeDefinition<?>> getLocalAttributeNames();
/**
* Copy the locally defined attributes from the argument to the receiver.
*/
public void copyAttributes(IAttributed fromAttributed);
}