org.hibernate.dialect.ResultColumnReferenceStrategy Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2010, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
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*/
package org.hibernate.dialect;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
/**
* Defines how we need to reference columns in the group-by, having, and order-by
* clauses.
*
* @author Steve Ebersole
*/
public class ResultColumnReferenceStrategy implements Serializable {
private static final Map INSTANCES = new HashMap();
/**
* This strategy says to reference the result columns by the qualified column name
* found in the result source. This strategy is not strictly allowed by ANSI SQL
* but is Hibernate's legacy behavior and is also the fastest of the strategies; thus
* it should be used if supported by the underlying database.
*/
public static final ResultColumnReferenceStrategy SOURCE = new ResultColumnReferenceStrategy( "source");
/**
* For databases which do not support {@link #SOURCE}, ANSI SQL defines two allowable
* approaches. One is to reference the result column by the alias it is given in the
* result source (if it is given an alias). This strategy says to use this approach.
*
* The other QNSI SQL compliant approach is {@link #ORDINAL}.
*/
public static final ResultColumnReferenceStrategy ALIAS = new ResultColumnReferenceStrategy( "alias" );
/**
* For databases which do not support {@link #SOURCE}, ANSI SQL defines two allowable
* approaches. One is to reference the result column by the ordinal position at which
* it appears in the result source. This strategy says to use this approach.
*
* The other QNSI SQL compliant approach is {@link #ALIAS}.
*/
public static final ResultColumnReferenceStrategy ORDINAL = new ResultColumnReferenceStrategy( "ordinal" );
static {
ResultColumnReferenceStrategy.INSTANCES.put( ResultColumnReferenceStrategy.SOURCE.name, ResultColumnReferenceStrategy.SOURCE );
ResultColumnReferenceStrategy.INSTANCES.put( ResultColumnReferenceStrategy.ALIAS.name, ResultColumnReferenceStrategy.ALIAS );
ResultColumnReferenceStrategy.INSTANCES.put( ResultColumnReferenceStrategy.ORDINAL.name, ResultColumnReferenceStrategy.ORDINAL );
}
private final String name;
public ResultColumnReferenceStrategy(String name) {
this.name = name;
}
public String toString() {
return name;
}
private Object readResolve() throws ObjectStreamException {
return parse( name );
}
public static ResultColumnReferenceStrategy parse(String name) {
return ( ResultColumnReferenceStrategy ) ResultColumnReferenceStrategy.INSTANCES.get( name );
}
}