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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 visigoths@visigoths.org.
  *
  * 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;
 
A class that allows one to associate custom data with a configuration, a template, or environment. It works pretty much like java.lang.ThreadLocal, a class that allows one to associate custom data with a thread.

Author(s):
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

Parameters:
scope one of SCOPE_ constants.
 
     public CustomAttribute(int scope) {
         if(scope !=  && 
            scope !=  && 
            scope != ) {
                 throw new IllegalArgumentException();
             }
        this. = scope;
    }
    
    
This method is invoked when get() is invoked without set(java.lang.Object) being invoked before it to define the value in the current scope. Override it to create the attribute value on-demand.

Returns:
the initial value for the custom attribute. By default returns null.
    protected Object create() {
        return null;
    }
    
    

Returns:
the value of the attribute in the context of the current environment.
Throws:
java.lang.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(this);
    }
    
    

Returns:
the value of a template-scope attribute in the context of a given template.
Throws:
java.lang.UnsupportedOperationException if this custom attribute is not a template-scope attribute
java.lang.NullPointerException if t is null
    public final Object get(Template t) {
        if( != ) {
            throw new UnsupportedOperationException("This is not a template-scope attribute");
        }
        return ((Configurable)t).getCustomAttribute(this);
    }
    
    
Sets the value of the attribute in the context of the current environment.

Parameters:
value the new value of the attribute
Throws:
java.lang.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(value);
    }

    
Sets the value of a template-scope attribute in the context of the given template.

Parameters:
value the new value of the attribute
t the template
Throws:
java.lang.UnsupportedOperationException if this custom attribute is not a template-scope attribute
java.lang.NullPointerException if t is null
    public final void set(Object valueTemplate t) {
        if( != ) {
            throw new UnsupportedOperationException("This is not a template-scope attribute");
        }
        ((Configurable)t).setCustomAttribute(value);
    }
    private Configurable getScopeConfigurable() {
        Configurable c = Environment.getCurrentEnvironment();
        if(c == null) {
            throw new IllegalStateException("No current environment");
        }
        switch() {
            case : {
                return c;
            }
            case : {
                return c.getParent();
            }
            case : {
                return c.getParent().getParent();
            }
            default: {
                throw new Error();
            }
        }
    }
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