StateVisitor.java

package org.dcache.services.info.base;

import java.util.Map;

/**
 * Interface for an algorithm that wishes to iterate over the current state.
 * Any algorithm that wishes to operate over the dCache state must implement
 * this interface.
 * <p>
 * Subclasses of StateValues will call the corresponding method.
 * <p>
 * StateComposite objects call visitCompositePreDescend() before visiting
 * their children. Once all children have been visited the StateComposite
 * will call visitCompositePostDescend().
 * <p>
 * For both StateComposite methods, the metadata parameter is either null or
 * references a keyword-value repository of metadata. This metadata is
 * specific for the particular StateComposite. The metadata is persistent and
 * independent of the actual contents of the State tree; it is linked to a
 * nodes path within the state.
 * <p>
 *
 * @author Paul Millar <paul.millar@desy.de>
 */
public interface StateVisitor extends StateGuide
{
    /* All subclasses of StateValue must be represented here. */

    void visitString(StatePath path, StringStateValue value);

    void visitInteger(StatePath path, IntegerStateValue value);

    void visitBoolean(StatePath path, BooleanStateValue value);

    void visitFloatingPoint(StatePath path, FloatingPointStateValue value);

    /* StateComposites call pre- and post- traversal */

    void visitCompositePreDescend(StatePath path, Map<String, String> metadata);

    void visitCompositePostDescend(StatePath path, Map<String, String> metadata);
}