Package 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, table

Constructor Summary

Constructors

Constructor	Description
FetchRequest(DatastoreClass classTable, org.datanucleus.FetchPlanForClass fpClass, org.datanucleus.ClassLoaderResolver clr, org.datanucleus.metadata.AbstractClassMetaData cmd, org.datanucleus.metadata.AbstractMemberMetaData[] mmds, org.datanucleus.metadata.AbstractMemberMetaData[] mmdsToStore)	Constructor.

Method Summary

Modifier and Type	Method	Description
void	execute(org.datanucleus.state.DNStateManager sm)	Method to execute the request - to be implemented by deriving classes.
protected int	processMembersOfClass(SelectStatement sqlStatement, org.datanucleus.FetchPlanForClass fpClass, org.datanucleus.metadata.AbstractMemberMetaData[] mmds, org.datanucleus.metadata.AbstractMemberMetaData[] mmdsToStore, DatastoreClass table, SQLTable sqlTbl, StatementClassMapping mappingDef, Collection fetchCallbacks, org.datanucleus.ClassLoaderResolver clr, List<Integer> memberNumbersToStore)	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.FetchPlanForClass fpClass,
                    org.datanucleus.ClassLoaderResolver clr,
                    org.datanucleus.metadata.AbstractClassMetaData cmd,
                    org.datanucleus.metadata.AbstractMemberMetaData[] mmds,
                    org.datanucleus.metadata.AbstractMemberMetaData[] mmdsToStore)

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

Parameters:

classTable - The Class Table representing the datastore table to retrieve

fpClass - FetchPlan for class

clr - ClassLoader resolver

cmd - ClassMetaData of the candidate

mmds - MetaData of the members to fetch

mmdsToStore - MetaData of the members to store

Method Detail

execute

public void execute(org.datanucleus.state.DNStateManager sm)

Description copied from class: Request

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

Specified by:

execute in class Request

Parameters:

sm - StateManager for the object in question.

processMembersOfClass

protected int processMembersOfClass(SelectStatement sqlStatement,
                                    org.datanucleus.FetchPlanForClass fpClass,
                                    org.datanucleus.metadata.AbstractMemberMetaData[] mmds,
                                    org.datanucleus.metadata.AbstractMemberMetaData[] mmdsToStore,
                                    DatastoreClass table,
                                    SQLTable sqlTbl,
                                    StatementClassMapping mappingDef,
                                    Collection fetchCallbacks,
                                    org.datanucleus.ClassLoaderResolver clr,
                                    List<Integer> memberNumbersToStore)

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

fpClass - FetchPlan for class

mmds - MetaData for the members to fetch

mmdsToStore - MetaData for the members to store

table - The table to look for member mappings

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

mappingDef - Mapping definition for the result

fetchCallbacks - Any additional required callbacks are added here

clr - ClassLoader resolver

memberNumbersToStore - Numbers of the members that need storing (populated by this call)

Returns:

Number of members being selected in the statement