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/*
* Copyright (c) 2003 The Visigoth Software Society. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Visigoth Software Society (http://www.visigoths.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the
* project contributors may be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
* 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
* nor may "FreeMarker" or "Visigoth" appear in their names
* without prior written permission of the Visigoth Software Society.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE VISIGOTH SOFTWARE SOCIETY OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Visigoth Software Society. For more
* information on the Visigoth Software Society, please see
* http://www.visigoths.org/
*/
package freemarker.core;
import freemarker.template.Template;
/**
* A class that allows one to associate custom data with a configuration,
* a template, or environment. It works pretty much like {@link ThreadLocal}, a
* class that allows one to associate custom data with a thread.
* @author Attila Szegedi
* @version $Id: CustomAttribute.java,v 1.3 2003/11/10 14:05:22 ddekany Exp $
*/
public class CustomAttribute
{
/**
* Constant used in the constructor specifying that this attribute is
* scoped by the environment.
*/
public static final int SCOPE_ENVIRONMENT = 0;
/**
* Constant used in the constructor specifying that this attribute is
* scoped by the template.
*/
public static final int SCOPE_TEMPLATE = 1;
/**
* Constant used in the constructor specifying that this attribute is
* scoped by the configuration.
*/
public static final int SCOPE_CONFIGURATION = 2;
// We use an internal key instead of 'this' so that malicious subclasses
// overriding equals() and hashCode() can't gain access to other attribute
// values. That's also the reason why get() and set() are marked final.
private final Object key = new Object();
private final int scope;
/**
* Creates a new custom attribute with the specified scope
* @param scope one of SCOPE_ constants.
*/
public CustomAttribute(int scope) {
if(scope != SCOPE_ENVIRONMENT &&
scope != SCOPE_TEMPLATE &&
scope != SCOPE_CONFIGURATION) {
throw new IllegalArgumentException();
}
this.scope = scope;
}
/**
* This method is invoked when {@link #get()} is invoked without
* {@link #set(Object)} being invoked before it to define the value in the
* current scope. Override it to create the attribute value on-demand.
* @return the initial value for the custom attribute. By default returns null.
*/
protected Object create() {
return null;
}
/**
* @return the value of the attribute in the context of the current environment.
* @throws IllegalStateException if there is no current environment (and
* hence also no current template and configuration), therefore the
* attribute's current scope object can't be resolved.
*/
public final Object get() {
return getScopeConfigurable().getCustomAttribute(key, this);
}
/**
* @return the value of a template-scope attribute in the context of a
* given template.
* @throws UnsupportedOperationException if this custom attribute is not a
* template-scope attribute
* @throws NullPointerException if t is null
*/
public final Object get(Template t) {
if(scope != SCOPE_TEMPLATE) {
throw new UnsupportedOperationException("This is not a template-scope attribute");
}
return ((Configurable)t).getCustomAttribute(key, this);
}
/**
* Sets the value of the attribute in the context of the current environment.
* @param value the new value of the attribute
* @throws IllegalStateException if there is no current environment (and
* hence also no current template and configuration), therefore the
* attribute's current scope object can't be resolved.
*/
public final void set(Object value) {
getScopeConfigurable().setCustomAttribute(key, value);
}
/**
* Sets the value of a template-scope attribute in the context of the given
* template.
* @param value the new value of the attribute
* @param t the template
* @throws UnsupportedOperationException if this custom attribute is not a
* template-scope attribute
* @throws NullPointerException if t is null
*/
public final void set(Object value, Template t) {
if(scope != SCOPE_TEMPLATE) {
throw new UnsupportedOperationException("This is not a template-scope attribute");
}
((Configurable)t).setCustomAttribute(key, value);
}
private Configurable getScopeConfigurable() {
Configurable c = Environment.getCurrentEnvironment();
if(c == null) {
throw new IllegalStateException("No current environment");
}
switch(scope) {
case SCOPE_ENVIRONMENT: {
return c;
}
case SCOPE_TEMPLATE: {
return c.getParent();
}
case SCOPE_CONFIGURATION: {
return c.getParent().getParent();
}
default: {
throw new Error();
}
}
}
}
