/*******************************************************************************
* Copyright (c) 2006, 2015 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
*
******************************************************************************/
package org.eclipse.persistence.jpa.jpql.parser;
import org.eclipse.persistence.jpa.jpql.WordParser;
/**
* This {@link ResultVariableFactory} creates a new {@link ResultVariable} when the portion of the
* query to parse starts with or without <b>AS</b>.
*
* @see ResultVariable
*
* @version 2.5
* @since 2.3
* @author Pascal Filion
*/
@SuppressWarnings("nls")
public final class ResultVariableFactory extends ExpressionFactory {
/**
* Caches the visitor that determines if the parent {@link Expression} is the top-level
* <code><b>SELECT</b></code> clause.
*/
private SelectClauseVisitor selectClauseVisitor;
/**
* The unique identifier of this {@link ResultVariableFactory}.
*/
public static final String ID = "result_variable";
/**
* Creates a new <code>ResultVariableFactory</code>.
*/
public ResultVariableFactory() {
super(ID, Expression.AS);
}
/**
* {@inheritDoc}
*/
@Override
protected AbstractExpression buildExpression(AbstractExpression parent,
WordParser wordParser,
String word,
JPQLQueryBNF queryBNF,
AbstractExpression expression,
boolean tolerant) {
SelectClauseVisitor visitor = selectClauseVisitor();
try {
if (expression != null) {
parent.accept(visitor);
if (!visitor.supported) {
expression = null;
}
}
}
finally {
visitor.supported = false;
}
// There was already an expression parsed, we'll assume it's a valid
// expression and it will have an identification variable, and the identifier is optional
// Example: "SELECT e.salary / 1000D n" or "SELECT e.salary / 1000D AS n"
if (((expression != null) || word.equalsIgnoreCase(Expression.AS)) &&
(word.indexOf(".") == -1)) {
ResultVariable resultVariable = new ResultVariable(parent, expression);
resultVariable.parse(wordParser, tolerant);
return resultVariable;
}
// Use the default factory
ExpressionFactory factory = getExpressionRegistry().getExpressionFactory(LiteralExpressionFactory.ID);
return factory.buildExpression(parent, wordParser, word, queryBNF, expression, tolerant);
}
private SelectClauseVisitor selectClauseVisitor() {
if (selectClauseVisitor == null) {
selectClauseVisitor = new SelectClauseVisitor();
}
return selectClauseVisitor;
}
/**
* This visitor determines whether the result variable should set the parsed expression as the
* select expression or not. The allowed locations are:
* <ul>
* <li>Root: To support parsing a JPQL fragment.</li>
* <li>Top-level <code><b>SELECT</b></code> clause: default valid location.</li>
* <li>Subquery <code><b>SELECT</b></code> clause: to support from within the
* <code><b>FROM</b></code> clause.</li>
* </ul>
*/
private static class SelectClauseVisitor extends AbstractExpressionVisitor {
/**
* Indicates if the result variable should have already parsed expression as its select expression.
*/
boolean supported;
/**
* {@inheritDoc}
*/
@Override
public void visit(JPQLExpression expression) {
this.supported = true;
}
/**
* {@inheritDoc}
*/
@Override
public void visit(SelectClause expression) {
this.supported = true;
}
/**
* {@inheritDoc}
*/
@Override
public void visit(SimpleSelectClause expression) {
this.supported = true;
}
}
}