io.permazen

Class ImportContext

java.lang.Object

io.permazen.ImportContext

public class ImportContext
extends Object

Context for importing plain (POJO) objects into a JTransaction.

Plain objects (POJO's) can be imported into a JTransaction to the extent that the POJO class and the corresponding Permazen model class share the same properties. The simplest example of this is when the POJO class is also the Permazen model class (implying a non-abstract class; see also @PermazenType.autogenNonAbstract()). Also possible are POJO classes and model classes that implement common Java interfaces.

The ObjId for the corresponding imported Permazen object is determined by the configured storageIdMapper. If storageIdMapper returns null, the POJO is not imported, and nulls replace any copied references to it; otherwise, the returned object must exist in the transaction. If storageIdMapper is itself null, the default behavior is to create a new Permazen object using JTransaction.create(Class), providing the POJO's class as the model class.

Instances ensure that an already-imported POJO will be recognized and not imported twice. Note this determination is based on object identity, not Object.equals(). The storageIdMapper is invoked at most once for any POJO.

Once the target object for a POJO has been identified, common properties are copied, overwriting any previous values. POJO properties that are not Permzen properties are ignored; conversely, properties that exist in the Permazen model object type but are missing in the POJO are left unmodified.

Permazen reference fields are automatically imported as POJO's, recursively. In other words, the entire transitive closure of POJO's reachable from an imported object is imported. Cycles in the graph of references are handled properly.

Conversion Details

Counter fields import from any Number property.

See Also:

ExportContext

Constructor Summary

Constructors

Constructor and Description
ImportContext(JTransaction jtx) Constructor.
ImportContext(JTransaction jtx, Function<Object,ObjId> storageIdMapper) Constructor.

Method Summary

Modifier and Type	Method and Description
Map<Object,ObjId>	getObjectMap() Get the mapping from already imported POJO's to their corresponding database objects.
JTransaction	getTransaction() Get the destination transaction for imported objects.
JObject	importPlain(Object obj) Import a plain Java object (POJO), along with all other objects reachable from it via copied reference fields.

Methods inherited from class java.lang.Object

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

Constructor Detail

ImportContext

public ImportContext(JTransaction jtx)

Constructor.

Uses a default storageIdMapper that creates new instances for imported objects via JTransaction.create(Class), using the Permazen model type found by Permazen.findJClass(Class) when given the POJO's class.

Parameters:

jtx - the transaction in which to import objects

Throws:

IllegalArgumentException - if jtx is null

ImportContext

public ImportContext(JTransaction jtx,
                     Function<Object,ObjId> storageIdMapper)

Constructor.

Parameters:

jtx - the transaction in which to import objects

storageIdMapper - function assigning ObjId's to imported objects (or null to skip the corresponding object)

Throws:

IllegalArgumentException - if either parameter is null

Method Detail

getTransaction

public JTransaction getTransaction()

Get the destination transaction for imported objects.

Returns:

associated transaction

getObjectMap

public Map<Object,ObjId> getObjectMap()

Get the mapping from already imported POJO's to their corresponding database objects.

Returns:

mapping from imported POJO to corresponding database object ID

importPlain

public JObject importPlain(Object obj)

Import a plain Java object (POJO), along with all other objects reachable from it via copied reference fields.

If obj has already been imported, the previously assigned JObject is returned.

Parameters:

obj - object to import; must not be null

Returns:

imported object, or null if the storageIdMapper returned null for obj

Throws:

DeletedObjectException - if storageIdMapper returns the object ID of a non-existent object

TypeNotInSchemaVersionException - if storageIdMapper returns an object ID that does not corresponding to any Permazen model class

IllegalArgumentException - if obj is null