001// ***************************************************************************************************************************
002// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
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004// * to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance            *
005// * with the License.  You may obtain a copy of the License at                                                              *
006// *                                                                                                                         *
007// *  http://www.apache.org/licenses/LICENSE-2.0                                                                             *
008// *                                                                                                                         *
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011// * specific language governing permissions and limitations under the License.                                              *
012// ***************************************************************************************************************************
013package org.apache.juneau.svl;
014
015/**
016 * Abstract superclass of all Simple Var Language variables that write their values directly to a writer.
017 *
018 * <p>
019 * Note the difference between this class and {@link SimpleVar} that returns simple string values.
020 * <br>Unlike the {@link SimpleVar} class, the output from this class cannot contain nested variables.
021 * <br>However, this class can be more efficient for variables that produce large amounts of output so that the creation
022 * of large in-memory strings is avoided.
023 *
024 * <p>
025 * Subclasses must implement the following method:
026 * <ul class='javatree'>
027 *    <li class='jm'>{@link #resolveTo(VarResolverSession, java.io.Writer, String)}
028 * </ul>
029 *
030 * <h5 class='section'>See Also:</h5><ul>
031 *    <li class='link'><a class="doclink" href="../../../../index.html#jm.SimpleVariableLanguage">Simple Variable Language</a>
032 * </ul>
033 */
034public abstract class StreamedVar extends Var {
035
036   /**
037    * Constructor.
038    *
039    * @param name The variable name (e.g. <js>"C"</js> for variables of the form <js>"$C{...}"</js>)
040    */
041   public StreamedVar(String name) {
042      super(name, true);
043   }
044
045   @Override /* Var */
046   public String resolve(VarResolverSession session, String arg) throws Exception {
047      throw new UnsupportedOperationException("Cannot call resolve() on StreamedVar class");
048   }
049}