org.hibernate.criterion.Projection Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
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* indicated by the @author tags or express copyright attribution
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* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
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* 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.
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*/
package org.hibernate.criterion;
import java.io.Serializable;
import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.type.Type;
/**
* An object-oriented representation of a query result set projection in a {@link Criteria} query.
* Built-in projection types are provided by the {@link Projections} factory class. This interface might be
* implemented by application classes that define custom projections.
*
* @author Gavin King
* @author Steve Ebersole
*
* @see Projections
* @see Criteria
*/
public interface Projection extends Serializable {
/**
* Render the SQL fragment to be used in the SELECT clause.
*
* @param criteria The local criteria to which this project is attached (for resolution).
* @param position The number of columns rendered in the SELECT clause before this projection. Generally
* speaking this is useful to ensure uniqueness of the individual columns aliases.
* @param criteriaQuery The overall criteria query instance.
* @return The SQL fragment to plug into the SELECT
* @throws HibernateException Indicates a problem performing the rendering
*/
public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery)
throws HibernateException;
/**
* Render the SQL fragment to be used in the GROUP BY clause
*
* @param criteria The local criteria to which this project is attached (for resolution).
* @param criteriaQuery The overall criteria query instance.
* @return The SQL fragment to plug into the GROUP BY
* @throws HibernateException Indicates a problem performing the rendering
*/
public String toGroupSqlString(Criteria criteria, CriteriaQuery criteriaQuery)
throws HibernateException;
/**
* Types returned by the rendered SQL {@link #toSqlString fragment}. In other words what are the types
* that would represent the values this projection asked to be pulled into the result set?
*
* @param criteria The local criteria to which this project is attached (for resolution).
* @param criteriaQuery The overall criteria query instance.
* @return The return types.
* @throws HibernateException Indicates a problem resolving the types
*/
public Type[] getTypes(Criteria criteria, CriteriaQuery criteriaQuery)
throws HibernateException;
/**
* Get the return types for a particular user-visible alias.
*
* Differs from {@link #getTypes(org.hibernate.Criteria, CriteriaQuery)} in that here we are only interested in
* the types related to the given criteria-level alias.
*
* @param alias The criteria-level alias for which to find types.
* @param criteria The local criteria to which this project is attached (for resolution).
* @param criteriaQuery The overall criteria query instance.
* @return The return types; expected to return null if this projection does not understand this alias.
* @throws HibernateException Indicates a problem resolving the types
*/
public Type[] getTypes(String alias, Criteria criteria, CriteriaQuery criteriaQuery)
throws HibernateException;
/**
* Get the SQL column aliases used by this projection for the columns it writes for inclusion into the
* SELECT clause ({@link #toSqlString}. Hibernate always uses column aliases to extract data from the
* JDBC {@link java.sql.ResultSet}, so it is important that these be implemented correctly in order for
* Hibernate to be able to extract these val;ues correctly.
*
* @param position Just as in {@link #toSqlString}, represents the number of columns rendered
* prior to this projection.
* @return The columns aliases.
*/
public String[] getColumnAliases(int position);
/**
* Get the SQL column aliases used by this projection for the columns it writes for inclusion into the
* SELECT clause ({@link #toSqlString} for a particular criteria-level alias.
*
* @param alias The criteria-level alias
* @param position Just as in {@link #toSqlString}, represents the number of columns rendered
* prior to this projection.
* @return The columns aliases pertaining to a particular criteria-level alias; expected to return null if
* this projection does not understand this alias.
*/
public String[] getColumnAliases(String alias, int position);
/**
* Get the criteria-level aliases for this projection (ie. the ones that will be passed to the
* {@link org.hibernate.transform.ResultTransformer})
*
* @return The aliases
*/
public String[] getAliases();
/**
* Is this projection fragment (SELECT clause) also part of the GROUP BY
*
* @return True if the projection is also part of the GROUP BY; false otherwise.
*/
public boolean isGrouped();
}