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package oracle.toplink.essentials.queryframework;
import java.util.*;
import oracle.toplink.essentials.mappings.converters.*;
import oracle.toplink.essentials.internal.helper.*;
import oracle.toplink.essentials.exceptions.*;
import oracle.toplink.essentials.internal.queryframework.*;
import oracle.toplink.essentials.internal.sessions.AbstractRecord;
/**
* <p><b>Purpose</b>:
* Concrete class to perform a direct read.
* <p>
* <p><b>Responsibilities</b>:
* Used in conjunction with DirectCollectionMapping.
* This can be used to read a single column of data (i.e. one field).
* A container (implementing Collection) of the data values is returned.
*
* @author Yvon Lavoie
* @since TOPLink/Java 1.0
*/
public class DirectReadQuery extends DataReadQuery {
/** Allows user defined conversion between the result value and the database value. */
protected Converter valueConverter;
/**
* PUBLIC:
* Initialize the state of the query.
*/
public DirectReadQuery() {
super();
}
/**
* PUBLIC:
* Initialize the query to use the specified SQL string.
*/
public DirectReadQuery(String sqlString) {
super(sqlString);
}
/**
* PUBLIC:
* Initialize the query to use the specified call.
*/
public DirectReadQuery(Call call) {
super(call);
}
/**
* PUBLIC:
* Return the converter on the query.
* A converter can be used to convert between the result value and database value.
*/
public Converter getValueConverter() {
return valueConverter;
}
/**
* PUBLIC:
* Set the converter on the query.
* A converter can be used to convert between the result value and database value.
*/
public void setValueConverter(Converter valueConverter) {
this.valueConverter = valueConverter;
}
/**
* INTERNAL:
* Used by cursored stream.
* Return the first field in the row.
*/
public Object buildObject(AbstractRecord row) {
Object value = row.get(row.getFields().firstElement());
if (getValueConverter() != null) {
value = getValueConverter().convertDataValueToObjectValue(value, session);
}
return value;
}
/**
* INTERNAL:
* The results are *not* in a cursor, build the collection.
*/
public Object executeNonCursor() throws DatabaseException, QueryException {
ContainerPolicy cp = getContainerPolicy();
Vector rows = getQueryMechanism().executeSelect();
Object result = cp.containerInstance(rows.size());
DatabaseField resultDirectField = null;
for (Enumeration stream = rows.elements(); stream.hasMoreElements();) {
AbstractRecord row = (AbstractRecord)stream.nextElement();
if (resultDirectField == null) {
resultDirectField = (DatabaseField)row.getFields().firstElement();
}
Object value = row.get(resultDirectField);
if (getValueConverter() != null) {
value = getValueConverter().convertDataValueToObjectValue(value, session);
}
cp.addInto(value, result, getSession());
}
return result;
}
}