org.datanucleus.store.rdbms.sql.expression.ColumnExpression Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of datanucleus-rdbms Show documentation
Plugin for DataNucleus providing persistence to RDBMS datastores.
There is a newer version: 6.0.7
/**********************************************************************
Copyright (c) 2008 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.expression;

import org.datanucleus.query.expression.Expression;
import org.datanucleus.store.rdbms.mapping.java.JavaTypeMapping;
import org.datanucleus.store.rdbms.sql.SQLStatement;
import org.datanucleus.store.rdbms.sql.SQLTable;
import org.datanucleus.store.rdbms.table.Column;

/**
 * Representation of a column expression.
 * Used within ObjectExpression for handling particular columns representing an object.
 */
public class ColumnExpression extends SQLExpression
{
    /** The column this represents. Only used when not a parameter. */
    Column column;

    Object value;

    boolean omitTableFromString = false;

    /**
     * Constructor for an SQL expression for a parameter.
     * @param stmt The statement
     * @param parameterName Name of the parameter
     * @param mapping Mapping for the column
     * @param value The value for the parameter for this column
     * @param colNumber Column number of the mapping being represented here
     */
    protected ColumnExpression(SQLStatement stmt, String parameterName, JavaTypeMapping mapping, Object value, int colNumber)
    {
        super(stmt, null, mapping);
        st.appendParameter(parameterName, mapping, value, colNumber);
    }

    /**
     * Constructor for an SQL expression for a column.
     * @param stmt The statement
     * @param table The table in the statement
     * @param col The column
     */
    protected ColumnExpression(SQLStatement stmt, SQLTable table, Column col)
    {
        super(stmt, table, null);
        this.column = col;
        st.append(toString());
    }

    /**
     * Constructor for an SQL expression for a literal value.
     * @param stmt The statement
     * @param value The literal value
     */
    protected ColumnExpression(SQLStatement stmt, Object value)
    {
        super(stmt, null, null);
        this.value = value;
        st.append(toString());
    }

    public BooleanExpression eq(SQLExpression expr)
    {
        return new BooleanExpression(this, Expression.OP_EQ, expr);
    }

    public BooleanExpression noteq(SQLExpression expr)
    {
        return new BooleanExpression(this, Expression.OP_NOTEQ, expr);
    }

    public void setOmitTableFromString(boolean omitTable)
    {
        // Part of UPDATE ... SET clause, and we can't use the table, so mark as ignoring, rollback the SQL, and regenerate
        this.omitTableFromString = omitTable;
        this.st.clearStatement();
        this.st.append(toString());
    }

    /**
     * Stringifier method to return this "column" in a form for use in SQL statements.
     * This can be of the following form(s)
     *      * TABLEALIAS.MYCOLUMN
     * MYTABLE.MYCOLUMN
     * 
     * @return The String form for use
     */
    public String toString()
    {
        if (value != null)
        {
            if (value instanceof String || value instanceof Character)
            {
                return "'" + value + "'";
            }

            return "" + value;
        }
        if (table == null)
        {
            // Column parameter
            return "?";
        }

        if (omitTableFromString)
        {
            return column.getIdentifier().toString();
        }

        if (table.getAlias() != null)
        {
            return table.getAlias() + "." + column.getIdentifier().toString();
        }

        return table.getTable() + "." + column.getIdentifier().toString();
    }
}