/*****************************************************************
* 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.
****************************************************************/
package org.apache.cayenne.access.translator.ejbql;
import org.apache.cayenne.ejbql.EJBQLBaseVisitor;
import org.apache.cayenne.ejbql.EJBQLExpression;
/**
* A translator of EJBQL SELECT statements into SQL.
*
* @since 3.0
*/
public class EJBQLSelectTranslator extends EJBQLBaseVisitor {
protected EJBQLTranslationContext context;
protected EJBQLSelectTranslator(EJBQLTranslationContext context) {
this.context = context;
}
EJBQLTranslationContext getContext() {
return context;
}
@Override
public boolean visitDistinct(EJBQLExpression expression) {
// "distinct" is appended via a marker as sometimes a later match on to-many would
// require a DISTINCT insertion.
context.pushMarker(context.makeDistinctMarker(), true);
context.append(" DISTINCT");
context.popMarker();
return true;
}
@Override
public boolean visitFrom(EJBQLExpression expression, int finishedChildIndex) {
context.append(" FROM");
context.setAppendingResultColumns(false);
expression.visit(context.getTranslatorFactory().getFromTranslator(context));
context.markCurrentPosition(context.makeWhereMarker());
context.markCurrentPosition(context.makeEntityQualifierMarker());
return false;
}
@Override
public boolean visitGroupBy(EJBQLExpression expression) {
context.append(" GROUP BY");
expression.visit(context.getTranslatorFactory().getGroupByTranslator(context));
return false;
}
@Override
public boolean visitHaving(EJBQLExpression expression) {
context.append(" HAVING");
expression.visit(context.getTranslatorFactory().getConditionTranslator(context));
return false;
}
@Override
public boolean visitOrderBy(EJBQLExpression expression) {
context.append(" ORDER BY");
expression.visit(context.getTranslatorFactory().getOrderByTranslator(context));
return false;
}
@Override
public boolean visitSelect(EJBQLExpression expression) {
// this ensures that result columns are appeneded only in top-level select, but
// not subselect (as 'visitSelect' is not called on subselect)
context.setAppendingResultColumns(true);
return true;
}
@Override
public boolean visitSelectClause(EJBQLExpression expression) {
context.append("SELECT");
context.markCurrentPosition(context.makeDistinctMarker());
return true;
}
@Override
public boolean visitSelectExpressions(EJBQLExpression expression) {
expression.visit(context.getTranslatorFactory().getSelectColumnsTranslator(
context));
return false;
}
@Override
public boolean visitWhere(EJBQLExpression expression) {
// "WHERE" is appended via a marker as it may have been already appended when an
// entity inheritance qualifier was applied.
context.pushMarker(context.makeWhereMarker(), true);
context.append(" WHERE");
context.popMarker();
if (context.findOrCreateMarkedBuffer(context.makeEntityQualifierMarker()).length() > 0) {
context.append(" AND");
}
expression.visit(context.getTranslatorFactory().getConditionTranslator(context));
return false;
}
}