Object-Relational Mapping (ORM) with AlloyDB Data Entities in Java

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 AlloyDB to generate an ORM of your AlloyDB repository with Hibernate.

Though Eclipse is the IDE of choice for this article, the CData JDBC Driver for AlloyDB works in any product that supports the Java Runtime Environment. In the Knowledge Base you will find tutorials to connect to AlloyDB 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/neon/stable/updates/" 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.alloydb.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 AlloyDB 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:

   • Hibernate version:: 5.2
   • Database dialect: Derby
   • Driver class: cdata.jdbc.alloydb.AlloyDBDriver

   • Connection URL: A JDBC URL, starting with jdbc:alloydb: and followed by a semicolon-separated list of connection properties.

     The following connection properties are usually required in order to connect to AlloyDB.

     • Server: The host name or IP of the server hosting the AlloyDB database.
     • User: The user which will be used to authenticate with the AlloyDB server.
     • Password: The password which will be used to authenticate with the AlloyDB server.

     You can also optionally set the following:

     • Database: The database to connect to when connecting to the AlloyDB Server. If this is not set, the user's default database will be used.
     • Port: The port of the server hosting the AlloyDB database. This property is set to 5432 by default.

     Authenticating with Standard Authentication

     Standard authentication (using the user/password combination supplied earlier) is the default form of authentication.

     No further action is required to leverage Standard Authentication to connect.

     Authenticating with pg_hba.conf Auth Schemes

     There are additional methods of authentication available which must be enabled in the pg_hba.conf file on the AlloyDB server.

     Find instructions about authentication setup on the AlloyDB Server here.

     Authenticating with MD5 Authentication

     This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to md5.

     Authenticating with SASL Authentication

     This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to scram-sha-256.

     Authenticating with Kerberos

     The authentication with Kerberos is initiated by AlloyDB Server when the ∏ is trying to connect to it. You should set up Kerberos on the AlloyDB Server to activate this authentication method. Once you have Kerberos authentication set up on the AlloyDB Server, see the Kerberos section of the help documentation for details on how to authenticate with Kerberos.

     Built-in Connection String Designer

     For assistance in constructing the JDBC URL, use the connection string designer built into the AlloyDB JDBC Driver. Either double-click the JAR file or execute the jar file from the command-line.

     java -jar cdata.jdbc.alloydb.jar

     Fill in the connection properties and copy the connection string to the clipboard.

     A typical JDBC URL is below:

     jdbc:alloydb:User=alloydb;Password=admin;Database=alloydb;Server=127.0.0.1;Port=5432

Connect Hibernate to AlloyDB 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. Set the Hibernate version to 5.2.
4. Click the Browse button and select the project.
5. 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).
6. In the Classpath tab, if there is nothing under User Entries, click Add External JARS and add the driver jar once more. Click OK once the configuration is done.
7. Expand the Database node of the newly created Hibernate configurations file.

Reverse Engineer AlloyDB 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 AlloyDB 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:

Execute SQL

Using the entity you created from the last step, you can now search and modify AlloyDB data: import java.util.*; import org.hibernate.Session; import org.hibernate.cfg.Configuration; import org.hibernate.query.Query; public class App { public static void main(final String[] args) { Session session = new Configuration().configure().buildSessionFactory().openSession(); String SELECT = "FROM Orders O WHERE ShipCountry = :ShipCountry"; Query q = session.createQuery(SELECT, Orders.class); q.setParameter("ShipCountry","USA"); List<Orders> resultList = (List<Orders>) q.list(); for(Orders s: resultList){ System.out.println(s.getShipName()); System.out.println(s.getShipCity()); } } }