src/main/java/freemarker/template/TemplateTransformModel.java

/*
 * Copyright (c) 2003 The Visigoth Software Society. All rights
 * reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 * 2. Redistributions in binary form must reproduce the above copyright
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 * 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.
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 * 4. Neither the name "FreeMarker", "Visigoth", nor any of the names of the 
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 * 5. Products derived from this software may not be called "FreeMarker" or "Visigoth"
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 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * This software consists of voluntary contributions made by many
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 * information on the Visigoth Software Society, please see
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 */

package freemarker.template;

import java.io.IOException;
import java.io.Writer;
import java.util.Map;

import freemarker.template.utility.DeepUnwrap;

/**
 * "transform" template language data type: user-defined directives 
 * (much like macros) specialized on filtering output; you should rather use the newer {@link TemplateDirectiveModel}
 * instead. This certainly will be deprecated in FreeMarker 2.4.
 * 
 * @author Attila Szegedi
 */
public interface TemplateTransformModel extends TemplateModel {

     /**
      * Returns a writer that will be used by the engine to feed the
      * transformation input to the transform. Each call to this method
      * must return a new instance of the writer so that the transformation
      * is thread-safe.
      * @param out the character stream to which to write the transformed output
      * @param args the arguments (if any) passed to the transformation as a 
      * map of key/value pairs where the keys are strings and the arguments are
      * TemplateModel instances. This is never null. If you need to convert the
      * template models to POJOs, you can use the utility methods in the 
      * {@link DeepUnwrap} class.
      * @return a writer to which the engine will feed the transformation 
      * input, or null if the transform does not support nested content (body).
      * The returned writer can implement the {@link TransformControl}
      * interface if it needs advanced control over the evaluation of the 
      * transformation body.
      */
     Writer getWriter(Writer out, Map args) 
         throws TemplateModelException, IOException;
}