Loader (Hibernate JavaDocs)
Date: 2012-04-05

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## org.hibernate.loader
Class Loader

    java.lang.Object
      org.hibernate.loader.Loader

Direct Known Subclasses:
  BasicLoader, CustomLoader

    public abstract class Loader

extends Object

Abstract superclass of object loading (and querying) strategies. This class implements useful common functionality that concrete loaders delegate to. It is not intended that this functionality would be directly accessed by client code. (Hence, all methods of this class are declared `protected` or `private`.) This class relies heavily upon the `Loadable` interface, which is the contract between this class and `EntityPersister`s that may be loaded by it.
The present implementation is able to load any number of columns of entities and at most one collection role per query.

See Also:
  `Loadable`

Field Summary
`protected static CoreMessageLogger` | `LOG`

Constructor Summary
`Loader(SessionFactoryImplementor factory)`

Method Summary
`protected String` | `applyLocks(String sql, LockOptions lockOptions, Dialect dialect)` Append `FOR UPDATE OF` clause, if necessary.
`protected void` | `applyPostLoadLocks(Object[] row, LockMode[] lockModesArray, SessionImplementor session)`
`protected boolean` | `areResultSetRowsTransformedImmediately()` Are rows transformed immediately after being read from the ResultSet?
`protected void` | `autoDiscoverTypes(ResultSet rs)`
`protected int` | `bindNamedParameters(PreparedStatement statement, Map namedParams, int startIndex, SessionImplementor session)` Bind named parameters to the JDBC prepared statement.
`protected int` | `bindParameterValues(PreparedStatement statement, QueryParameters queryParameters, int startIndex, SessionImplementor session)` Bind all parameter values into the prepared statement in preparation for execution.
`protected int` | `bindPositionalParameters(PreparedStatement statement, QueryParameters queryParameters, int startIndex, SessionImplementor session)` Bind positional parameter values to the JDBC prepared statement.
`protected void` | `checkScrollability()` Check whether the current loader can support returning ScrollableResults.
`protected List` | `doList(SessionImplementor session, QueryParameters queryParameters)` Actually execute a query, ignoring the query cache
`protected void` | `extractKeysFromResultSet(Loadable[] persisters, QueryParameters queryParameters, ResultSet resultSet, SessionImplementor session, EntityKey[] keys, LockMode[] lockModes, List hydratedObjects)`
`protected String[]` | `getAliases()` Get the SQL table aliases of entities whose associations are subselect-loadable, returning null if this loader does not support subselect loading
`protected abstract CollectionAliases[]` | `getCollectionAliases()`
`protected int[]` | `getCollectionOwners()` Get the index of the entity that owns the collection, or -1 if there is no owner in the query results (ie.
`protected CollectionPersister[]` | `getCollectionPersisters()` An (optional) persister for a collection to be initialized; only collection loaders return a non-null value
`protected int[][]` | `getCompositeKeyManyToOneTargetIndices()`
`protected abstract EntityAliases[]` | `getEntityAliases()` Get the result set descriptor
`protected boolean[]` | `getEntityEagerPropertyFetches()` An array indicating whether the entities have eager property fetching enabled.
`protected abstract Loadable[]` | `getEntityPersisters()` An array of persisters of entity classes contained in each row of results; implemented by all subclasses
`SessionFactoryImplementor` | `getFactory()`
`protected abstract LockMode[]` | `getLockModes(LockOptions lockOptions)` What lock options does this load entities with?
`int[]` | `getNamedParameterLocs(String name)`
`protected EntityType[]` | `getOwnerAssociationTypes()` An array of the owner types corresponding to the `getOwners()` returns.
`protected int[]` | `getOwners()` An array of indexes of the entity that owns a one-to-one association to the entity at the given index (-1 if there is no "owner").
`protected String` | `getQueryIdentifier()` Identifies the query for statistics reporting, if null, no statistics will be reported
`protected Object` | `getResultColumnOrRow(Object[] row, ResultTransformer transformer, ResultSet rs, SessionImplementor session)` Get the actual object that is returned in the user-visible result list.
`protected List` | `getResultList(List results, ResultTransformer resultTransformer)`
`protected Object[]` | `getResultRow(Object[] row, ResultSet rs, SessionImplementor session)`
`protected String[]` | `getResultRowAliases()` Returns the aliases that corresponding to a result row.
`protected ResultSet` | `getResultSet(PreparedStatement st, boolean autodiscovertypes, boolean callable, RowSelection selection, SessionImplementor session)` Fetch a `PreparedStatement`, call `setMaxRows` and then execute it, advance to the first result and return an SQL `ResultSet`
`protected abstract String` | `getSQLString()` The SQL query string to be called; implemented by all subclasses
`protected boolean` | `hasSubselectLoadableCollections()`
`protected boolean[]` | `includeInResultRow()`
`protected boolean` | `isSingleRowLoader()` Return false is this loader is a batch entity loader
`protected boolean` | `isSubselectLoadingEnabled()`
`protected List` | `list(SessionImplementor session, QueryParameters queryParameters, Set querySpaces, Type[] resultTypes)` Return the query results, using the query cache, called by subclasses that implement cacheable queries
`void` | `loadCollection(SessionImplementor session, Serializable id, Type type)` Called by subclasses that initialize collections
`void` | `loadCollectionBatch(SessionImplementor session, Serializable[] ids, Type type)` Called by wrappers that batch initialize collections
`protected void` | `loadCollectionSubselect(SessionImplementor session, Serializable[] ids, Object[] parameterValues, Type[] parameterTypes, Map namedParameters, Type type)` Called by subclasses that batch initialize collections
`protected List` | `loadEntity(SessionImplementor session, Object key, Object index, Type keyType, Type indexType, EntityPersister persister)` Called by subclasses that load entities
`protected List` | `loadEntity(SessionImplementor session, Object id, Type identifierType, Object optionalObject, String optionalEntityName, Serializable optionalIdentifier, EntityPersister persister, LockOptions lockOptions)` Called by subclasses that load entities
`List` | `loadEntityBatch(SessionImplementor session, Serializable[] ids, Type idType, Object optionalObject, String optionalEntityName, Serializable optionalId, EntityPersister persister, LockOptions lockOptions)` Called by wrappers that batch load entities
`Object` | `loadSequentialRowsForward(ResultSet resultSet, SessionImplementor session, QueryParameters queryParameters, boolean returnProxies)` Loads a single logical row from the result set moving forward.
`Object` | `loadSequentialRowsReverse(ResultSet resultSet, SessionImplementor session, QueryParameters queryParameters, boolean returnProxies, boolean isLogicallyAfterLast)` Loads a single logical row from the result set moving forward.
`Object` | `loadSingleRow(ResultSet resultSet, SessionImplementor session, QueryParameters queryParameters, boolean returnProxies)` Loads a single row from the result set.
`protected boolean` | `needsFetchingScroll()` Does the result set to be scrolled contain collection fetches?
`protected void` | `postInstantiate()` Calculate and cache select-clause suffixes.
`protected PreparedStatement` | `prepareQueryStatement(QueryParameters queryParameters, boolean scroll, SessionImplementor session)` Obtain a `PreparedStatement` with all parameters pre-bound.
`protected String` | `preprocessSQL(String sql, QueryParameters parameters, Dialect dialect)` Modify the SQL, adding lock hints and comments, if necessary
`protected ResultTransformer` | `resolveResultTransformer(ResultTransformer resultTransformer)` Determine the actual ResultTransformer that will be used to transform query results.
`protected ScrollableResults` | `scroll(QueryParameters queryParameters, Type[] returnTypes, HolderInstantiator holderInstantiator, SessionImplementor session)` Return the query results, as an instance of `ScrollableResults`
`String` | `toString()`
`protected boolean` | `upgradeLocks()` Does this query return objects that might be already cached by the session, whose lock mode may need upgrading

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

### LOG

    protected static final CoreMessageLogger LOG

Constructor Detail

### Loader

    public Loader(SessionFactoryImplementor factory)

Method Detail

### getSQLString

    protected abstract String getSQLString()

  The SQL query string to be called; implemented by all subclasses

  Returns:
    The sql command this loader should use to get its `ResultSet`.

### getEntityPersisters

    protected abstract Loadable[] getEntityPersisters()

  An array of persisters of entity classes contained in each row of results; implemented by all subclasses

  Returns:
    The entity persisters.

### getEntityEagerPropertyFetches

    protected boolean[] getEntityEagerPropertyFetches()

  An array indicating whether the entities have eager property fetching enabled.

  Returns:
    Eager property fetching indicators.

### getOwners

    protected int[] getOwners()

  An array of indexes of the entity that owns a one-to-one association to the entity at the given index (-1 if there is no "owner"). The indexes contained here are relative to the result of `getEntityPersisters()`.

  Returns:
    The owner indicators (see discussion above).

### getOwnerAssociationTypes

    protected EntityType[] getOwnerAssociationTypes()

  An array of the owner types corresponding to the `getOwners()` returns. Indices indicating no owner would be null here.

  Returns:
    The types for the owners.

### getCollectionPersisters

    protected CollectionPersister[] getCollectionPersisters()

  An (optional) persister for a collection to be initialized; only collection loaders return a non-null value

### getCollectionOwners

    protected int[] getCollectionOwners()

  Get the index of the entity that owns the collection, or -1 if there is no owner in the query results (ie. in the case of a collection initializer) or no collection.

### getCompositeKeyManyToOneTargetIndices

    protected int[][] getCompositeKeyManyToOneTargetIndices()

### getLockModes

    protected abstract LockMode[] getLockModes(LockOptions lockOptions)

  What lock options does this load entities with?

  Parameters:
    `lockOptions` - a collection of lock options specified dynamically via the Query interface

### applyLocks

    protected String applyLocks(String sql,
                                LockOptions lockOptions,
                                Dialect dialect)
                         throws HibernateException

  Append `FOR UPDATE OF` clause, if necessary. This empty superclass implementation merely returns its first argument.

  Throws:
    `HibernateException`

### upgradeLocks

    protected boolean upgradeLocks()

  Does this query return objects that might be already cached by the session, whose lock mode may need upgrading

### isSingleRowLoader

    protected boolean isSingleRowLoader()

  Return false is this loader is a batch entity loader

### getAliases

    protected String[] getAliases()

  Get the SQL table aliases of entities whose associations are subselect-loadable, returning null if this loader does not support subselect loading

### preprocessSQL

    protected String preprocessSQL(String sql,
                                   QueryParameters parameters,
                                   Dialect dialect)
                            throws HibernateException

  Modify the SQL, adding lock hints and comments, if necessary

  Throws:
    `HibernateException`

### loadSingleRow

    public Object loadSingleRow(ResultSet resultSet,
                                SessionImplementor session,
                                QueryParameters queryParameters,
                                boolean returnProxies)
                         throws HibernateException

  Loads a single row from the result set. This is the processing used from the ScrollableResults where no collection fetches were encountered.

  Parameters:
    `resultSet` - The result set from which to do the load.
    `session` - The session from which the request originated.
    `queryParameters` - The query parameters specified by the user.
    `returnProxies` - Should proxies be generated
  Returns:
    The loaded "row".
  Throws:
    `HibernateException`

### loadSequentialRowsForward

    public Object loadSequentialRowsForward(ResultSet resultSet,
                                            SessionImplementor session,
                                            QueryParameters queryParameters,
                                            boolean returnProxies)
                                     throws HibernateException

  Loads a single logical row from the result set moving forward. This is the processing used from the ScrollableResults where there were collection fetches encountered; thus a single logical row may have multiple rows in the underlying result set.

  Parameters:
    `resultSet` - The result set from which to do the load.
    `session` - The session from which the request originated.
    `queryParameters` - The query parameters specified by the user.
    `returnProxies` - Should proxies be generated
  Returns:
    The loaded "row".
  Throws:
    `HibernateException`

### loadSequentialRowsReverse

    public Object loadSequentialRowsReverse(ResultSet resultSet,
                                            SessionImplementor session,
                                            QueryParameters queryParameters,
                                            boolean returnProxies,
                                            boolean isLogicallyAfterLast)
                                     throws HibernateException

  Loads a single logical row from the result set moving forward. This is the processing used from the ScrollableResults where there were collection fetches encountered; thus a single logical row may have multiple rows in the underlying result set.

  Parameters:
    `resultSet` - The result set from which to do the load.
    `session` - The session from which the request originated.
    `queryParameters` - The query parameters specified by the user.
    `returnProxies` - Should proxies be generated
  Returns:
    The loaded "row".
  Throws:
    `HibernateException`

### extractKeysFromResultSet

    protected void extractKeysFromResultSet(Loadable[] persisters,
                                            QueryParameters queryParameters,
                                            ResultSet resultSet,
                                            SessionImplementor session,
                                            EntityKey[] keys,
                                            LockMode[] lockModes,
                                            List hydratedObjects)
                                     throws SQLException

  Throws:
    `SQLException`

### applyPostLoadLocks

    protected void applyPostLoadLocks(Object[] row,
                                      LockMode[] lockModesArray,
                                      SessionImplementor session)

### isSubselectLoadingEnabled

    protected boolean isSubselectLoadingEnabled()

### hasSubselectLoadableCollections

    protected boolean hasSubselectLoadableCollections()

### resolveResultTransformer

    protected ResultTransformer resolveResultTransformer(ResultTransformer resultTransformer)

  Determine the actual ResultTransformer that will be used to transform query results.

  Parameters:
    `resultTransformer` - the specified result transformer
  Returns:
    the actual result transformer

### getResultList

    protected List getResultList(List results,
                                 ResultTransformer resultTransformer)
                          throws QueryException

  Throws:
    `QueryException`

### areResultSetRowsTransformedImmediately

    protected boolean areResultSetRowsTransformedImmediately()

  Are rows transformed immediately after being read from the ResultSet?

  Returns:
    true, if getResultColumnOrRow() transforms the results; false, otherwise

### getResultRowAliases

    protected String[] getResultRowAliases()

  Returns the aliases that corresponding to a result row.

  Returns:
    Returns the aliases that corresponding to a result row.

### getResultColumnOrRow

    protected Object getResultColumnOrRow(Object[] row,
                                          ResultTransformer transformer,
                                          ResultSet rs,
                                          SessionImplementor session)
                                   throws SQLException,
                                          HibernateException

  Get the actual object that is returned in the user-visible result list. This empty implementation merely returns its first argument. This is overridden by some subclasses.

  Throws:
    `SQLException`
    `HibernateException`

### includeInResultRow

    protected boolean[] includeInResultRow()

### getResultRow

    protected Object[] getResultRow(Object[] row,
                                    ResultSet rs,
                                    SessionImplementor session)
                             throws SQLException,
                                    HibernateException

  Throws:
    `SQLException`
    `HibernateException`

### prepareQueryStatement

    protected final PreparedStatement prepareQueryStatement(QueryParameters queryParameters,
                                                            boolean scroll,
                                                            SessionImplementor session)
                                                     throws SQLException,
                                                            HibernateException

  Obtain a `PreparedStatement` with all parameters pre-bound. Bind JDBC-style `?` parameters, named parameters, and limit parameters.

  Throws:
    `SQLException`
    `HibernateException`

### bindParameterValues

    protected int bindParameterValues(PreparedStatement statement,
                                      QueryParameters queryParameters,
                                      int startIndex,
                                      SessionImplementor session)
                               throws SQLException

  Bind all parameter values into the prepared statement in preparation for execution.

  Parameters:
    `statement` - The JDBC prepared statement
    `queryParameters` - The encapsulation of the parameter values to be bound.
    `startIndex` - The position from which to start binding parameter values.
    `session` - The originating session.
  Returns:
    The number of JDBC bind positions actually bound during this method execution.
  Throws:
    `SQLException` - Indicates problems performing the binding.

### bindPositionalParameters

    protected int bindPositionalParameters(PreparedStatement statement,
                                           QueryParameters queryParameters,
                                           int startIndex,
                                           SessionImplementor session)
                                    throws SQLException,
                                           HibernateException

  Bind positional parameter values to the JDBC prepared statement.

  Positional parameters are those specified by JDBC-style ? parameters in the source query. It is (currently) expected that these come before any named parameters in the source query.

  Parameters:
    `statement` - The JDBC prepared statement
    `queryParameters` - The encapsulation of the parameter values to be bound.
    `startIndex` - The position from which to start binding parameter values.
    `session` - The originating session.
  Returns:
    The number of JDBC bind positions actually bound during this method execution.
  Throws:
    `SQLException` - Indicates problems performing the binding.
    `HibernateException` - Indicates problems delegating binding to the types.

### bindNamedParameters

    protected int bindNamedParameters(PreparedStatement statement,
                                      Map namedParams,
                                      int startIndex,
                                      SessionImplementor session)
                               throws SQLException,
                                      HibernateException

  Bind named parameters to the JDBC prepared statement.

  This is a generic implementation, the problem being that in the general case we do not know enough information about the named parameters to perform this in a complete manner here. Thus this is generally overridden on subclasses allowing named parameters to apply the specific behavior. The most usual limitation here is that we need to assume the type span is always one...

  Parameters:
    `statement` - The JDBC prepared statement
    `namedParams` - A map of parameter names to values
    `startIndex` - The position from which to start binding parameter values.
    `session` - The originating session.
  Returns:
    The number of JDBC bind positions actually bound during this method execution.
  Throws:
    `SQLException` - Indicates problems performing the binding.
    `HibernateException` - Indicates problems delegating binding to the types.

### getNamedParameterLocs

    public int[] getNamedParameterLocs(String name)

### getResultSet

    protected final ResultSet getResultSet(PreparedStatement st,
                                           boolean autodiscovertypes,
                                           boolean callable,
                                           RowSelection selection,
                                           SessionImplementor session)
                                    throws SQLException,
                                           HibernateException

  Fetch a `PreparedStatement`, call `setMaxRows` and then execute it, advance to the first result and return an SQL `ResultSet`

  Throws:
    `SQLException`
    `HibernateException`

### autoDiscoverTypes

    protected void autoDiscoverTypes(ResultSet rs)

### loadEntity

    protected final List loadEntity(SessionImplementor session,
                                    Object id,
                                    Type identifierType,
                                    Object optionalObject,
                                    String optionalEntityName,
                                    Serializable optionalIdentifier,
                                    EntityPersister persister,
                                    LockOptions lockOptions)
                             throws HibernateException

  Called by subclasses that load entities

  Parameters:
    `persister` - only needed for logging
    `lockOptions` -
  Throws:
    `HibernateException`

### loadEntity

    protected final List loadEntity(SessionImplementor session,
                                    Object key,
                                    Object index,
                                    Type keyType,
                                    Type indexType,
                                    EntityPersister persister)
                             throws HibernateException

  Called by subclasses that load entities

  Parameters:
    `persister` - only needed for logging
  Throws:
    `HibernateException`

### loadEntityBatch

    public final List loadEntityBatch(SessionImplementor session,
                                      Serializable[] ids,
                                      Type idType,
                                      Object optionalObject,
                                      String optionalEntityName,
                                      Serializable optionalId,
                                      EntityPersister persister,
                                      LockOptions lockOptions)
                               throws HibernateException

  Called by wrappers that batch load entities

  Parameters:
    `persister` - only needed for logging
    `lockOptions` -
  Throws:
    `HibernateException`

### loadCollection

    public final void loadCollection(SessionImplementor session,
                                     Serializable id,
                                     Type type)
                              throws HibernateException

  Called by subclasses that initialize collections

  Throws:
    `HibernateException`

### loadCollectionBatch

    public final void loadCollectionBatch(SessionImplementor session,
                                          Serializable[] ids,
                                          Type type)
                                   throws HibernateException

  Called by wrappers that batch initialize collections

  Throws:
    `HibernateException`

### loadCollectionSubselect

    protected final void loadCollectionSubselect(SessionImplementor session,
                                                 Serializable[] ids,
                                                 Object[] parameterValues,
                                                 Type[] parameterTypes,
                                                 Map namedParameters,
                                                 Type type)
                                          throws HibernateException

  Called by subclasses that batch initialize collections

  Throws:
    `HibernateException`

### list

    protected List list(SessionImplementor session,
                        QueryParameters queryParameters,
                        Set querySpaces,
                        Type[] resultTypes)
                 throws HibernateException

  Return the query results, using the query cache, called by subclasses that implement cacheable queries

  Throws:
    `HibernateException`

### doList

    protected List doList(SessionImplementor session,
                          QueryParameters queryParameters)
                   throws HibernateException

  Actually execute a query, ignoring the query cache

  Throws:
    `HibernateException`

### checkScrollability

    protected void checkScrollability()
                               throws HibernateException

  Check whether the current loader can support returning ScrollableResults.

  Throws:
    `HibernateException`

### needsFetchingScroll

    protected boolean needsFetchingScroll()

  Does the result set to be scrolled contain collection fetches?

  Returns:
    True if it does, and thus needs the special fetching scroll functionality; false otherwise.

### scroll

    protected ScrollableResults scroll(QueryParameters queryParameters,
                                       Type[] returnTypes,
                                       HolderInstantiator holderInstantiator,
                                       SessionImplementor session)
                                throws HibernateException

  Return the query results, as an instance of `ScrollableResults`

  Parameters:
    `queryParameters` - The parameters with which the query should be executed.
    `returnTypes` - The expected return types of the query
    `holderInstantiator` - If the return values are expected to be wrapped in a holder, this is the thing that knows how to wrap them.
    `session` - The session from which the scroll request originated.
  Returns:
    The ScrollableResults instance.
  Throws:
    `HibernateException` - Indicates an error executing the query, or constructing the ScrollableResults.

### postInstantiate

    protected void postInstantiate()

  Calculate and cache select-clause suffixes. Must be called by subclasses after instantiation.

### getEntityAliases

    protected abstract EntityAliases[] getEntityAliases()

  Get the result set descriptor

### getCollectionAliases

    protected abstract CollectionAliases[] getCollectionAliases()

### getQueryIdentifier

    protected String getQueryIdentifier()

  Identifies the query for statistics reporting, if null, no statistics will be reported

### getFactory

    public final SessionFactoryImplementor getFactory()

### toString

    public String toString()

  Overrides:
    `toString` in class `Object`

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