odata2-lib/odata-api/src/main/java/org/apache/olingo/odata2/api/uri/expression/Visitable.java

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package org.apache.olingo.odata2.api.uri.expression;

import org.apache.olingo.odata2.api.exception.ODataApplicationException;

/**
 * The interface {@link Visitable} is part of the visitor pattern used to traverse
 * the expression tree build from a $filter expression string or $orderby expression string.
 * It is implemented by each class used as node in an expression tree.
 * 
 * @see ExpressionVisitor
 * 
 */
public interface Visitable {

  /**
   * Method {@link #accept(ExpressionVisitor)} is called when traversing the expression tree. This method is invoked on
   * each
   * expression used as node in an expression tree. The implementations should
   * behave as follows:
   * <li>Call accept on all sub nodes and store the returned Objects
   * <li>Call the appropriate method on the {@link ExpressionVisitor} instance and provide the stored objects to that
   * instance
   * <li>Return the object which should be passed to the processing algorithm of the parent expression node
   * <br>
   * <br>
   * @param visitor
   * Object ( implementing {@link ExpressionVisitor}) whose methods are called during traversing a expression node of
   * the expression tree.
   * @return
   * Object which should be passed to the processing algorithm of the parent expression node
   * @throws ExceptionVisitExpression
   * Exception occurred the OData library while traversing the tree
   * @throws ODataApplicationException
   * Exception thrown by the application who implemented the visitor
   */
  Object accept(ExpressionVisitor visitor) throws ExceptionVisitExpression, ODataApplicationException;
}