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Texo/EntityManagerObjectStore
Contents
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.
(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);