package org.apache.commons.ognl;

 /*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *   http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 import org.apache.commons.ognl.enhance.ExpressionAccessor;

 /**

  * JJTree interface for AST nodes, as modified to handle the OGNL operations getValue and setValue. JJTree's original

  * comment: All AST nodes must implement this interface. It provides basic machinery for constructing the parent and

  * child relationships between nodes.

  * 

  * @author Luke Blanshard (blanshlu@netscape.net)

  * @author Drew Davidson (drew@ognl.org)

  */

 public interface Node

     extends JavaSource

 {

     /**

      * This method is called after the node has been made the current node. It indicates that child nodes can now be

      * added to it.

      */

     void jjtOpen();

     /**

      * This method is called after all the child nodes have been added.

      */

     void jjtClose();

     /**

      * This pair of methods are used to inform the node of its parent.

      */

     void jjtSetParent( Node n );

     Node jjtGetParent();

     /**

      * This method tells the node to add its argument to the node's list of children.

      */

     void jjtAddChild( Node n, int i );

     /**

      * This method returns a child node. The children are numbered from zero, left to right.

      */

     Node jjtGetChild( int i );

     /** Return the number of children the node has. */

     int jjtGetNumChildren();

     // OGNL additions to Node:

     /**

      * Extracts the value from the given source object that is appropriate for this node within the given context.

      */

     Object getValue( OgnlContext context, Object source )

         throws OgnlException;

     /**

      * Sets the given value in the given target as appropriate for this node within the given context.

      */

     void setValue( OgnlContext context, Object target, Object value )

         throws OgnlException;

     /**

      * Gets the compiled bytecode enhanced expression accessor for getting/setting values.

      * 

      * @return The accessor for this node, or null if none has been compiled for it.

      */

     ExpressionAccessor getAccessor();

     /**

      * Sets a new compiled accessor for this node expression.

      * 

      * @param accessor The compiled representation of this node.

      */

     void setAccessor( ExpressionAccessor accessor );

     /**

      * Supports the Visitor pattern. The method which corresponds to

      * the runtime type of this Node will be called.

      *

      * @param visitor The visitor to accept.

      * @param data    The second parameter to pass through to visitor.visit

      * @param <R>     The return type of the visitor.visit method.

      * @param <P>     The type of the second parameter type.

      * @return the value returned by visitor.visit

      * @throws NullPointerException if visitor is null

      * @throws RuntimeException     if visitor.visit throws an exception.

      */

     <R, P> R accept( NodeVisitor<? extends R, ? super P> visitor, P data )

         throws OgnlException;

 }