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package org.apache.juneau.svl;

import static org.apache.juneau.internal.StringUtils.*;

/**
 * Interface for the resolution of vars that can have one or more keys where the first non-null resolution is returned.
 *
 * <p>
 * For example, to resolve the system property <js>"myProperty"</js> but then resolve <js>"myProperty2"</js> if the
 * property doesn't exist: <js>"$S{myProperty1,myProperty2}"</js>
 *
 * <p>
 * Subclasses must implement the following method:
 * <ul class='javatree'>
 * 	<li class='jm'>{@link #resolve(VarResolverSession, String)}
 * </ul>
 *
 * <ul class='seealso'>
 * 	<li class='link'>{@doc jm.SimpleVariableLanguage}
 * 	<li class='extlink'>{@source}
 * </ul>
 */
public abstract class MultipartResolvingVar extends SimpleVar {

	/**
	 * Constructor.
	 *
	 * @param name The name of this variable.
	 */
	public MultipartResolvingVar(String name) {
		super(name);
	}

	@Override /* Var*/
	public String doResolve(VarResolverSession session, String s) throws Exception {
		int i = s.indexOf(',');
		if (i == -1)
			return resolve(session, s.trim());
		for (String s2 : split(s)) {
			String v = resolve(session, s2);
			if (v != null)
				return v;
		}
		return null;
	}
}
