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Plugin for DataNucleus providing persistence to RDBMS datastores.

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/**********************************************************************
Copyright (c) 2009 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
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.

Contributors:
    ...
**********************************************************************/
package org.datanucleus.store.rdbms.sql.operation;

import java.util.ArrayList;
import java.util.List;

import org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping;
import org.datanucleus.store.rdbms.sql.expression.SQLExpression;
import org.datanucleus.store.rdbms.sql.expression.SQLLiteral;
import org.datanucleus.store.rdbms.sql.expression.StringExpression;
import org.datanucleus.store.rdbms.sql.expression.StringLiteral;

/**
 * Implementation of a conversion from a NumericExpression to a StringExpression.
 * Results in CAST(expr AS VARCHAR(4000))
 * The second expression argument is not used; the first arg is converted to a StringExpression.
 */
public class NumericToStringOperation implements SQLOperation
{
    /* (non-Javadoc)
     * @see org.datanucleus.store.rdbms.sql.operation.SQLOperation#getExpression(org.datanucleus.store.rdbms.sql.expression.SQLExpression, org.datanucleus.store.rdbms.sql.expression.SQLExpression)
     */
    public SQLExpression getExpression(SQLExpression expr, SQLExpression expr2)
    {
        JavaTypeMapping m = expr.getSQLStatement().getSQLExpressionFactory().getMappingForType(String.class, false);
        if (expr instanceof SQLLiteral)
        {
            // Just convert the literal value directly
            if (((SQLLiteral)expr).getValue() == null)
            {
                return new StringLiteral(expr.getSQLStatement(), m, null, null);
            }
            return new StringLiteral(expr.getSQLStatement(), m, ((SQLLiteral)expr).getValue().toString(), null);
        }

        List args = new ArrayList();
        args.add(expr);
        List types = new ArrayList();
        types.add("VARCHAR(4000)");
        return new StringExpression(expr.getSQLStatement(), m, "CAST", args, types);
    }
}