Introduction
For one of my projects I had to decide for an object relational mapping (ORM) solution to be used in a web environment. There is not much to think about when deciding which framework to use. Yet, I wanted to try out Eclipse CDO [1] as an alternative to, for example, hibernate.
The project is powered by CDO since a year, now. And it has proven to be a lightweight ORM solution. No JPA annotations, just design your EMF model, create instances and let CDO handle the rest...
A full request/response cycle
The following sketch shows the involved steps when a user (HTML5 client/browser) sends a HTTP request to a service that consumes the CDO storage.
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| Request/Response process |
The web application is driven by (JAX-RS) REST services, so any call/request is served by the appropriate REST service.
For each call which requires DB access, a new CDO transaction is opened, the request is processed, the result is converted to JSON and the transaction closed/committed.
Conversion of EMF model instances is done using Eclipse Texo [2] in most scenarios, but special view models are also created using a JSON java library like org.json [3].
The overall setup of the CDO server/backend:
- CDO DBStore with embedded H2 RDBMS
- disabled auditing, disabled branching (not needed by project)
- one resource per user, central meta data resources (for example, user accounts, roles, permissions management), managed in different resource folders
- simulation of a document oriented database
- simplifies authorization a lot
- nginx proxy for simple HTTPS setup
- OSGi environment with embedded Jetty, packaged using a maven/tycho enabled Eclipse RCP product build
- a very limited virtual host (for now): 512 MB RAM, single core Xeon CPU, Ubuntu 16.04 server
Have you ever considered using CDO as an ORM solution? Or are you already using it in a web context? What are your experiences?
Links
[1] Eclipse CDO: https://www.eclipse.org/cdo/
[2] Eclipse Texo: https://wiki.eclipse.org/Texo
[3] org.json: https://github.com/stleary/JSON-java
