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package org.apache.juneau.svl;

/**
 * Abstract superclass of all Simple Var Language variables that write their values directly to a writer.
 *
 * <p>
 * Note the difference between this class and {@link SimpleVar} that returns simple string values.
 * <br>Unlike the {@link SimpleVar} class, the output from this class cannot contain nested variables.
 * <br>However, this class can be more efficient for variables that produce large amounts of output so that the creation
 * of large in-memory strings is avoided.
 *
 * <p>
 * Subclasses must implement the following method:
 * <ul class='javatree'>
 * 	<li class='jm'>{@link #resolveTo(VarResolverSession, java.io.Writer, String)}
 * </ul>
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc juneau-marshall.SimpleVariableLanguage.SvlVariables}
 * </ul>
 */
public abstract class StreamedVar extends Var {

	/**
	 * Constructor.
	 *
	 * @param name The variable name (e.g. <js>"C"</js> for variables of the form <js>"$C{...}"</js>)
	 */
	public StreamedVar(String name) {
		super(name, true);
	}

	@Override /* Var */
	public String resolve(VarResolverSession session, String arg) throws Exception {
		throw new UnsupportedOperationException("Cannot call resolve() on StreamedVar class");
	}
}
