org.hibernate.criterion
Interface Projection

All Superinterfaces:

Serializable

All Known Subinterfaces:

EnhancedProjection

All Known Implementing Classes:

AggregateProjection, AliasedProjection, AvgProjection, CountProjection, Distinct, IdentifierProjection, ProjectionList, Property, PropertyProjection, RowCountProjection, SimpleProjection, SQLProjection

public interface Projection
extends Serializable

An object-oriented representation of a query result set projection in a Criteria query. Built-in projection types are provided by the Projections factory class. This interface might be implemented by application classes that define custom projections.

Author:

Gavin King, Steve Ebersole

See Also:

Projections, Criteria

Method Summary

String[]	getAliases() Get the criteria-level aliases for this projection (ie.
String[]	getColumnAliases(int position) Get the SQL column aliases used by this projection for the columns it writes for inclusion into the SELECT clause (toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery).
String[]	getColumnAliases(String alias, int position) Get the SQL column aliases used by this projection for the columns it writes for inclusion into the SELECT clause (toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery) for a particular criteria-level alias.
Type[]	getTypes(Criteria criteria, CriteriaQuery criteriaQuery) Types returned by the rendered SQL fragment.
Type[]	getTypes(String alias, Criteria criteria, CriteriaQuery criteriaQuery) Get the return types for a particular user-visible alias.
boolean	isGrouped() Is this projection fragment (SELECT clause) also part of the GROUP BY
String	toGroupSqlString(Criteria criteria, CriteriaQuery criteriaQuery) Render the SQL fragment to be used in the GROUP BY clause
String	toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery) Render the SQL fragment to be used in the SELECT clause.

Method Detail

toSqlString

String toSqlString(Criteria criteria,
                   int position,
                   CriteriaQuery criteriaQuery)
                   throws HibernateException

Render the SQL fragment to be used in the SELECT clause.

Parameters:

criteria - The local criteria to which this project is attached (for resolution).

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.

criteriaQuery - The overall criteria query instance.

Returns:

The SQL fragment to plug into the SELECT

Throws:

HibernateException - Indicates a problem performing the rendering

toGroupSqlString

String toGroupSqlString(Criteria criteria,
                        CriteriaQuery criteriaQuery)
                        throws HibernateException

Render the SQL fragment to be used in the GROUP BY clause

Parameters:

criteria - The local criteria to which this project is attached (for resolution).

criteriaQuery - The overall criteria query instance.

Returns:

The SQL fragment to plug into the GROUP BY

Throws:

HibernateException - Indicates a problem performing the rendering

getTypes

Type[] getTypes(Criteria criteria,
                CriteriaQuery criteriaQuery)
                throws HibernateException

Types returned by the rendered SQL fragment. In other words what are the types that would represent the values this projection asked to be pulled into the result set?

Parameters:

criteria - The local criteria to which this project is attached (for resolution).

criteriaQuery - The overall criteria query instance.

Returns:

The return types.

Throws:

HibernateException - Indicates a problem resolving the types

getTypes

Type[] getTypes(String alias,
                Criteria criteria,
                CriteriaQuery criteriaQuery)
                throws HibernateException

Get the return types for a particular user-visible alias.

Differs from getTypes(org.hibernate.Criteria, CriteriaQuery) in that here we are only interested in the types related to the given criteria-level alias.

Parameters:

alias - The criteria-level alias for which to find types.

criteria - The local criteria to which this project is attached (for resolution).

criteriaQuery - The overall criteria query instance.

Returns:

The return types; expected to return null if this projection does not understand this alias.

Throws:

HibernateException - Indicates a problem resolving the types

getColumnAliases

String[] getColumnAliases(int position)

Get the SQL column aliases used by this projection for the columns it writes for inclusion into the SELECT clause (toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery). Hibernate always uses column aliases to extract data from the JDBC ResultSet, so it is important that these be implemented correctly in order for Hibernate to be able to extract these val;ues correctly.

Parameters:

position - Just as in toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery), represents the number of columns rendered prior to this projection.

Returns:

The columns aliases.

getColumnAliases

String[] getColumnAliases(String alias,
                          int position)

Get the SQL column aliases used by this projection for the columns it writes for inclusion into the SELECT clause (toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery) for a particular criteria-level alias.

Parameters:

alias - The criteria-level alias

position - Just as in toSqlString(org.hibernate.Criteria, int, org.hibernate.criterion.CriteriaQuery), represents the number of columns rendered prior to this projection.

Returns:

The columns aliases pertaining to a particular criteria-level alias; expected to return null if this projection does not understand this alias.

getAliases

String[] getAliases()

Get the criteria-level aliases for this projection (ie. the ones that will be passed to the ResultTransformer)

Returns:

The aliases

isGrouped

boolean isGrouped()

Is this projection fragment (SELECT clause) also part of the GROUP BY

Returns:

True if the projection is also part of the GROUP BY; false otherwise.