Texo/EntityManagerObjectStore

Introduction

The Texo ObjectStore concept integrates the model layer with JPA. It provides the following functionality:

• It makes it possible to query using an EClass
• Supports cross reference queries
• Supports (de-)serialization with (de-)resolving of references in the XML/XMI against the ObjectStore (the database)

If you want more specific Dao functionality, check out the Texo Dao support.

Jar files/Plugins

The Texo Object Store is defined in the org.eclipse.emf.texo.server plugin which is part of the Texo runtime feature (see Download & Install).

Creating an Object Store

An Object Store instance can be created directly if you have an EntityManager available:

EntityManagerObjectStore objectStore = new EntityManagerObjectStore();
objectStore.setEntityManager(entityManager);
// the URI is used for de-resolving references when serializing to XML, see below
objectStore.setUri("http://jpa.test");

Note that for the ObjectStore to be able to read the model layer: the model package class needs to be loaded and initialized, just touching it is enough, for example:

LibraryModelPackage.initialize();

Cross Reference Queries

The ObjectStore allows you to retrieve all the objects which reference a certain target object:

// get maximum 3 referers and include containment referers
List<Object> referers = objectStore.getReferingObjects(target, 3, true);

See the ObjectStore getReferingObjects api and the isReferenced method.

EntityManager

The ObjectStore needs an EntityManager to perform database queries. An EntityManager is set in the same was as described for Dao's, see here for more details.

(De-)Serializing XML with correct id's

When (de-)serializing XML most of the time the references to other objects should be serialized as external references (the referenced object is not present in the XML). When de-serializing the XML these references should be correctly resolved to objects again. This resolving needs to be able to read the objects from the database again.

This (de-)resolving of references while reading from the database is done using the ObjectStore. It is quite simple:

// serialize a set of objects to xml, use XMI (specified by the second parameter
String xml = objectStore.toXML(objects, true);
// and get it back
List<Object> objects = objectStore.fromXML(xml, true);