/******************************************************************************* | |
* Copyright (c) 1998, 2013 Oracle and/or its affiliates. All rights reserved. | |
* This program and the accompanying materials are made available under the | |
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 | |
* which accompanies this distribution. | |
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html | |
* and the Eclipse Distribution License is available at | |
* http://www.eclipse.org/org/documents/edl-v10.php. | |
* | |
* Contributors: | |
* Oracle - initial API and implementation from Oracle TopLink | |
******************************************************************************/ | |
package org.eclipse.persistence.internal.expressions; | |
import java.util.*; | |
import org.eclipse.persistence.expressions.*; | |
/** | |
* Used to itterate an expression tree, through inner subclasses. | |
*/ | |
public abstract class ExpressionIterator { | |
/** Allow the iteration to build a result. */ | |
protected Object result; | |
/** Some iterations require a statement. */ | |
protected SQLSelectStatement statement; | |
/** Some iterations require a more general parameter. */ | |
protected Object parameter; | |
/** | |
* Block constructor comment. | |
*/ | |
public ExpressionIterator() { | |
super(); | |
} | |
public Object getResult() { | |
return result; | |
} | |
public SQLSelectStatement getStatement() { | |
return statement; | |
} | |
/** | |
* Answers if this expression has already been visited. | |
* For a faster iteration override to insure expressions are only | |
* visited/processed once. | |
*/ | |
public boolean hasAlreadyVisited(Expression expression) { | |
return false; | |
} | |
/** | |
* INTERNAL: | |
* This method must be defined by subclasses to implement the logic of the iteratation. | |
*/ | |
public abstract void iterate(Expression expression); | |
/** | |
* INTERNAL: | |
*/ | |
public void iterateOn(Vector expressions) { | |
for (Enumeration expressionEnum = expressions.elements(); expressionEnum.hasMoreElements();) { | |
iterate((Expression)expressionEnum.nextElement()); | |
} | |
} | |
/** | |
* INTERNAL: | |
* Return the call. | |
*/ | |
public void iterateOn(Expression expression) { | |
expression.iterateOn(this); | |
} | |
public void setResult(Object result) { | |
this.result = result; | |
} | |
public void setStatement(SQLSelectStatement statement) { | |
this.statement = statement; | |
} | |
/** | |
* Normally an Iterator will not go into the where clause of | |
* an SQLSubSelectExpression. I.e. when aliasing the parent statement | |
* is aliased before the subselects may even be normalized. An iterator to | |
* alias the SubSelect must be run later. | |
*/ | |
public boolean shouldIterateOverSubSelects() { | |
return false; | |
} | |
} |