Development with Oracle Open Source: Not just JET

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1 Development with Oracle Open Source: Not just JET Style Luc Bors eproseed Utrecht - Netherlands Keywords Oracle JET, Glassfish, MySQL, EclipseLink, Howto, Multitenant,Tips and Tricks. Introduction For one of our customers we developed a multitenant solution that was completely based on Oracle open source products. In this session you will learn how, in this real life project, we used Glassfish, MySQL, EclipseLink and Oracle's JavaScript Extension Toolkit (JET) to build a multitenant application. You will not only get insight in the application architecture, but you will also learn about the tools we used. You will get valuable tips and tricks and learn about the pitfalls that we encountered during the implementation of this solution. A Brief History The customer, Smart Data City, is a network organization that invests in improving cities by means of technology, user experience and interaction, combined with change management, They operate on the edge of the digital and physical world. Their goal is to make relevant information available at the right time at the right moment to the right stakeholder. For this project eproseed was asked to build a solution that enables Smart Data City to conduct questionnaires that can be used to determine the smartness of cities. The outcome of these questionnaires can be used for several purposes. This year for instance it will be used to determine the winner of the smartest city of the Netherlands contest. When we initially started the project we planned to use an Oracle JET based front-end and an Oracle cloud-based back-end, using products such as "Oracle Database Cloud Service" and "Oracle Java Cloud Service". Soon after starting there were some issues with the sponsoring of the project at the customer. That is why we started looking for a cost-effective alternative and found it in a combination of "Oracle JavaScript Extension Toolkit" (JET), GlassFish, EclipseLink, and MySQL all are free Oracle open source products, which we then used to develop the required solution. A good reader immediately notices that we used two separate IDE s for development. Main reason for this is that JDev has EclipseLink support, JAX-RS support, etc. but we couldn t use it for JET (at least not really) After switching to GlassFish the development of the REST Services was still kept in JDeveloper. For Oracle JET, the preferred IDE is NetBeans, making its use obvious. Figure 1: Solution Architecture

2 The next sections will discuss the used components in somewhat more detail and give you an overview of the solution. Multilanguage and Multitenant The solution was initially not setup to be multilingual nor multi-location nor multitenant. This requirement was added after a while. The multilanguage part could easily be solved by using browser locale and resource bundles. This is more or less built in functionality of the Oracle JET framework. You simply define a resource bundle per supported language and at runtime the framework does the rest. Figure 2: Multilanguage The multitenant part was more complex. The requirement was to store data per tenant, so the solution we choose was to use a table-per-tenant approach. Based on a tenantdiscriminator the user was routed to his/her specific tenant tables. This feature is perfectly supported by EclipseLink and works more or less out of the box. After implementing this for the first two tenants (NL and UK) it is very easy to add extra tenants. The only thing that needs to be done for that is the creation of an extra set of tables for that particular tenant. Figure 3: Multitenancy Model

3 The actual implementation of multitenancy in the Java code is done in the EclipseLink entities. It is a very easy solution. By adding two annotations, EclipseLink knows exactly what to do. Figure 4: Annotations for multitenancy Just before calling the EclipseLink query, you need to make sure to set the tenant correctly. This is something that you should do on the EntityManager that is responsible for managing the POJOs that are mapped onto relational tables and executing the SQL statement. Figure 5: Setting the Tenant Implementation of the User Interface Oracle JET is a modular toolkit allowing developers to use as much or as little of the features as they desire. This project was the first project were we used it on, and it didn t take much time to get used to working with Oracle JET. The great advantage of Oracle JET is this: The toolkit supports the development of web applications using JavaScript and also includes a compilation of commonly used open source JavaScript Frameworks like Knockout, RequireJS and Figure 6: Example from the Solution JQuery.

4 Consequently, there is already a large collection of knowledge and documentation in the community. In addition, the built-in two-way binding provides a powerful way for creating highly responsive User Experience. All this has helped us to create the application user interface quickly. Oracle JET also makes it pretty easy to work with the REST services that were running on GlassFish. For instance, for the graphs, all data is retrieved with one single REST call, after which the data is processed to be used in the actual graphs. The following code sample from reporting.js shows this. Figure 7: Get the Report Data The actual rendering of the graphs in reporting.html is based on a knockout foreach construction. This actually takes all entries in the categories array, and stamps out a graph for them. It is a very powerful approach which allows you create a fancy dashboard with just a bit of code, as you can see in the following code sample: Figure 8: Example of knockout foreach Some things to keep in mind Especially when we just started the project we ran into many pitfalls and encountered several technical challenges. First of all, we had to learn Oracle JET. We never used this toolkit before but it did note take too long before we were able to make things work. The next pitfall was when we decided to switch from Oracle WebLogic Server and Oracle XE Database to Glassfish and MySQL. One would expect that this is an easy switch, but it proved to be more

5 challenging than expected in terms of portability. What runs on WebLogic does not necessarily run on Glassfish right away, and what works with Oracle Database is not always a fit for MySQL. In the end we managed to make it work. You also need to consider security. There is now code, running on the client, that is directly calling REST services, instead of code that is running on a webserver that is calling REST services. Another point that should be considered is browser caching and cache busting: The JET application is cached in the browser, as it is static content. There are ways to circumvent this, and especially when deploying new versions of the application, it is a must that the browser is forced to refresh the application. We had to find out how to tell the browser that the application is a different version and force it to refresh. This is typically configured in the main.js file where you can configure the behavior of require.js Figure 9: Cache busting Summary With a full stack of Oracle Open Source products, we were able to implement a solution for our customer that not only was free of license fees, but also proved to be stable and reliable in production environment. The drawback of this is ofcourse that you give up support, and that you miss out on specific features that are only part of licensed products. In this short paper there is too little room to discuss all the details of this solution. During the presentation you will hear many more inside details. Feel free to contact me if you have any questions. Contact: Luc Bors eproseed Dijkgraafpolder, ZC Houten, Netherlands Telefon: +31 (0) luc.bors@eproseed.com Internet: