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Object-Relational Mapping (ORM) with Open Exchange Rates Data Entities in Java

Object-relational mapping (ORM) techniques make it easier to work with relational data sources and can bridge your logical business model with your physical storage model. Follow this tutorial to integrate connectivity to Open Exchange Rates data into a Java-based ORM framework, Hibernate.

You can use Hibernate to map object-oriented domain models to a traditional relational database. The tutorial below shows how to use the CData JDBC Driver for Open Exchange Rates to generate an ORM of your Open Exchange Rates repository with Hibernate.

Though Eclipse is the IDE of choice for this article, the CData JDBC Driver for Open Exchange Rates works in any product that supports the Java Runtime Environment. In the Knowledge Base you will find tutorials to connect to Open Exchange Rates data from IntelliJ IDEA and NetBeans.

Install Hibernate

Follow the steps below to install the Hibernate plug-in in Eclipse.

  1. In Eclipse, navigate to Help -> Install New Software.
  2. Enter "http://download.jboss.org/jbosstools/updates/stable/" in the Work With box.
  3. Enter "Hibernate" into the filter box.
  4. Select Hibernate Tools.

Start A New Project

Follow the steps below to add the driver JARs in a new project.

  1. Create a new project. Select Java Project as your project type and click Next. Enter a project name and click Finish.
  2. Right-click the project and click Properties. Click Java Build Path and then open the Libraries tab.
  3. Click Add External JARs to add the cdata.jdbc.openexchangerates.jar library, located in the lib subfolder of the installation directory.

Add a Hibernate Configuration File

Follow the steps below to configure connection properties to Open Exchange Rates data.

  1. Right-click on the new project and select New -> Hibernate -> Hibernate Configuration File (cfg.xml).
  2. Select src as the parent folder and click Next.
  3. Input the following values:

    • Database dialect: SQL Server
    • Driver class: cdata.jdbc.openexchangerates.OpenExchangeRatesDriver
    • Connection URL: A JDBC URL, starting with jdbc:openexchangerates: and followed by a semicolon-separated list of connection properties.

      The Open Exchange Rates API supports basic authentication with an App Id. After you register, your App Id is displayed in your account dashboard. Set this to the AppId connection property.

      A typical JDBC URL is below:

      jdbc:openexchangerates:AppId=abc1234;

Connect Hibernate to Open Exchange Rates Data

Follow the steps below to select the configuration you created in the previous step.

  1. Switch to the Hibernate Configurations perspective: Window -> Open Perspective -> Hibernate.
  2. Right-click on the Hibernate Configurations panel and click Add Configuration.
  3. Click the Browse button and select the project.
  4. For the Configuration file field, click Setup -> Use Existing and select the location of the hibernate.cfg.xml file (inside src folder in this demo).
  5. Expand the Database node of the newly created Hibernate configurations file.

Reverse Engineer Open Exchange Rates Data

Follow the steps below to generate the reveng.xml configuration file. You will specify the tables you want to access as objects.

  1. Switch back to the Package Explorer.
  2. Right-click your project, select New -> Hibernate -> Hibernate Reverse Engineering File (reveng.xml). Click Next.
  3. Select src as the parent folder and click Next.
  4. In the Console configuration drop-down menu, select the Hibernate configuration file you created above and click Refresh.
  5. Expand the node and choose the tables you want to reverse engineer. Click Finish when you are done.

Configure Hibernate to Run

Follow the steps below to generate plain old Java objects (POJO) for the Open Exchange Rates tables.

  1. From the menu bar, click Run -> Hibernate Code Generation -> Hibernate Code Generation Configurations.
  2. In the Console configuration drop-down menu, select the Hibernate configuration file you created in the previous section. Click Browse by Output directory and select src.
  3. Enable the Reverse Engineer from JDBC Connection checkbox. Click the Setup button, click Use Existing, and select the location of the hibernate.reveng.xml file (inside src folder in this demo).
  4. In the Exporters tab, check Domain code (.java) and Hibernate XML Mappings (hbm.xml).
  5. Click Run.

One or more POJOs are created based on the reverse-engineering setting in the previous step.

Insert Mapping Tags

For each mapping you have generated, you will need to create a mapping tag in hibernate.cfg.xml to point Hibernate to your mapping resource. Open hibernate.cfg.xml and insert the mapping tags as so:

cdata.openexchangerates.OpenExchangeRatesDriver jdbc:openexchangerates:AppId=abc1234; org.hibernate.dialect.SQLServerDialect

Execute CRUD Commands

Using the entity you created from the last step, you can now perform Select commands. For example:

import java.util.*; import org.hibernate.*; import org.hibernate.cfg.Configuration; public class App { public static void main(final String[] args) { Session session = new Configuration().configure().buildSessionFactory().openSession(); String SELECT = "FROM Projects"; Query q = session.createQuery(SELECT); List resultList = (List) q.list(); for(Projects s: resultList){ System.out.println(s.getId()); System.out.println(s.getStatistics_ViewCount()); } } }
 
 
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