org.datanucleus.store.rdbms.request

Class FetchRequest

java.lang.Object

org.datanucleus.store.rdbms.request.Request

org.datanucleus.store.rdbms.request.FetchRequest

public class FetchRequest
extends Request

Class to retrieve the fields of an object of a specified class from the datastore. If some of those fields are themselves persistent objects then this can optionally retrieve fields of those objects in the same fetch.

Any surrogate version stored in this table will be fetched *if* the object being updated doesn't already have a value for it. If the caller wants the surrogate version to be updated then they should nullify the "transactional" version before calling.

Field Summary

Fields inherited from class org.datanucleus.store.rdbms.request.Request

key, LOCALISER, table

Constructor Summary

Constructors

Constructor and Description
FetchRequest(DatastoreClass classTable, org.datanucleus.metadata.AbstractMemberMetaData[] mmds, org.datanucleus.metadata.AbstractClassMetaData cmd, org.datanucleus.ClassLoaderResolver clr) Constructor, taking the table.

Method Summary

Methods

Modifier and Type	Method and Description
void	execute(org.datanucleus.state.ObjectProvider op) Method to execute the request - to be implemented by deriving classes.
protected int	processMembersOfClass(SQLStatement sqlStatement, org.datanucleus.metadata.AbstractMemberMetaData[] mmds, DatastoreClass table, SQLTable sqlTbl, StatementClassMapping mappingDef, Collection fetchCallbacks, org.datanucleus.ClassLoaderResolver clr) Method to process the supplied members of the class, adding to the SQLStatement as required.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FetchRequest

public FetchRequest(DatastoreClass classTable,
            org.datanucleus.metadata.AbstractMemberMetaData[] mmds,
            org.datanucleus.metadata.AbstractClassMetaData cmd,
            org.datanucleus.ClassLoaderResolver clr)

Constructor, taking the table. Uses the structure of the datastore table to build a basic query.

Parameters:

classTable - The Class Table representing the datastore table to retrieve

mmds - MetaData of the fields/properties to retrieve

cmd - ClassMetaData of objects being fetched

clr - ClassLoader resolver

Method Detail

execute

public void execute(org.datanucleus.state.ObjectProvider op)

Description copied from class: Request

Method to execute the request - to be implemented by deriving classes.

Specified by:

execute in class Request

Parameters:

op - The ObjectProvider for the object in question.

processMembersOfClass

protected int processMembersOfClass(SQLStatement sqlStatement,
                        org.datanucleus.metadata.AbstractMemberMetaData[] mmds,
                        DatastoreClass table,
                        SQLTable sqlTbl,
                        StatementClassMapping mappingDef,
                        Collection fetchCallbacks,
                        org.datanucleus.ClassLoaderResolver clr)

Method to process the supplied members of the class, adding to the SQLStatement as required. Can recurse if some of the requested fields are persistent objects in their own right, so we take the opportunity to retrieve some of their fields.

Parameters:

sqlStatement - Statement being built

mmds - Meta-data for the required fields/properties

table - The table to look for member mappings

sqlTbl - The table in the SQL statement to use for selects

fetchCallbacks - Any additional required callbacks are added here

Returns:

Number of fields being fetched