OptionalOrElseMethod.java

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Copyright (c) 2016 Andy Jefferson and others. All rights reserved.
Licensed 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
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
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Contributors:
    ...
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package org.datanucleus.store.rdbms.sql.method;

import java.util.List;

import org.datanucleus.exceptions.NucleusException;
import org.datanucleus.store.rdbms.mapping.java.BigDecimalMapping;
import org.datanucleus.store.rdbms.mapping.java.BigIntegerMapping;
import org.datanucleus.store.rdbms.mapping.java.BooleanMapping;
import org.datanucleus.store.rdbms.mapping.java.DoubleMapping;
import org.datanucleus.store.rdbms.mapping.java.FloatMapping;
import org.datanucleus.store.rdbms.mapping.java.IntegerMapping;
import org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping;
import org.datanucleus.store.rdbms.mapping.java.LongMapping;
import org.datanucleus.store.rdbms.mapping.java.OptionalMapping;
import org.datanucleus.store.rdbms.mapping.java.ShortMapping;
import org.datanucleus.store.rdbms.mapping.java.StringMapping;
import org.datanucleus.store.rdbms.sql.expression.CaseBooleanExpression;
import org.datanucleus.store.rdbms.sql.expression.CaseExpression;
import org.datanucleus.store.rdbms.sql.expression.CaseNumericExpression;
import org.datanucleus.store.rdbms.sql.expression.CaseStringExpression;
import org.datanucleus.store.rdbms.sql.expression.NullLiteral;
import org.datanucleus.store.rdbms.sql.expression.OptionalExpression;
import org.datanucleus.store.rdbms.sql.expression.SQLExpression;

/**
 * Method for evaluating {optionalExpr1}.orElse().
 * Returns a XXXExpression representing "CASE WHEN col IS NOT NULL THEN col ELSE otherVal END".
 */
public class OptionalOrElseMethod extends AbstractSQLMethod
{
    /* (non-Javadoc)
     * @see org.datanucleus.store.rdbms.sql.method.SQLMethod#getExpression(org.datanucleus.store.rdbms.sql.expression.SQLExpression, java.util.List)
     */
    public SQLExpression getExpression(SQLExpression expr, List<SQLExpression> args)
    {
        if (args != null && args.size() != 1)
        {
            throw new NucleusException("Optional.orElse should be passed 1 argument");
        }

        SQLExpression elseExpr = args.get(0);

        OptionalMapping opMapping = (OptionalMapping) ((OptionalExpression)expr).getJavaTypeMapping();
        JavaTypeMapping javaMapping = opMapping.getWrappedMapping();
        SQLExpression getExpr = exprFactory.newExpression(stmt, expr.getSQLTable(),javaMapping);
        SQLExpression isNotNullExpr = exprFactory.newExpression(stmt, expr.getSQLTable(),javaMapping).ne(new NullLiteral(stmt, javaMapping, null, null));
        if (javaMapping instanceof StringMapping)
        {
            return new CaseStringExpression(new SQLExpression[] {isNotNullExpr}, new SQLExpression[] {getExpr}, elseExpr);
        }
        else if (javaMapping instanceof IntegerMapping || javaMapping instanceof LongMapping || javaMapping instanceof ShortMapping ||
                javaMapping instanceof FloatMapping || javaMapping instanceof DoubleMapping || javaMapping instanceof BigIntegerMapping || javaMapping instanceof BigDecimalMapping)
        // TODO Maybe use javaMapping.getJavaType compared to Number to avoid the check above
        {
            return new CaseNumericExpression(new SQLExpression[] {isNotNullExpr}, new SQLExpression[] {getExpr}, elseExpr);
        }
        else if (javaMapping instanceof BooleanMapping)
        {
            return new CaseBooleanExpression(new SQLExpression[] {isNotNullExpr}, new SQLExpression[] {getExpr}, elseExpr);
        }
        return new CaseExpression(new SQLExpression[] {isNotNullExpr}, new SQLExpression[] {getExpr}, elseExpr);
    }
}