Microservice: Create JPA App Using Jakarta Persistence API in Payara Micro

 

Before We Begin:

In this tutorial, we will configure this application with the following components in mind:

• The microservice application will be a Mavenized Java application.
• We will use MySQL DB Server as a relational database.
• The JDBC data source will be a transactional data source (XADataSource).

JDBC Driver Library Configuration With Maven

You need a JDBC driver to connect your Java application with a relational database. The driver is usually provided by the database vendor. Fortunately, most database vendors have released their JDBC drivers to a Maven repository.

If you use Maven to build your application, you can add your JDBC driver by adding code that is similar to the following example to your pom.xml file.

XML

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    <dependencyManagement>

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        <dependencies>

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            <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->

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            <dependency>

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                <groupId>mysql</groupId>

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                <artifactId>mysql-connector-java</artifactId>

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                <version>8.0.19</version>

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            </dependency>

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        </dependencies>

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    </dependencyManagement>

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    <dependencies>

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        <dependency>

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            <groupId>mysql</groupId>

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            <artifactId>mysql-connector-java</artifactId>

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        </dependency>

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    </dependencies>

With Maven, the JDBC driver file will be copied to the WEB-INF/lib folder of your application WAR file during the package build phase.

Configuring a Database Datasource

In the Payara Blog, a data source is configured inside the web.xml file. In this example, there is another alternative for creating a data source configuration. The example below demonstrates a basic data source configuration pattern  for the payara-resource.xml file inside the src/main/java/webapp/WEB-INF folder:

XML

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    <!DOCTYPE resources  PUBLIC  "-//Payara.fish//DTD Payara Server 4 Resource Definitions//EN"  "https://raw.githubusercontent.com/payara/Payara-Community-Documentation/master/docs/modules/ROOT/pages/schemas/payara-resources_1_6.dtd">

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    <resources>

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        <jdbc-resource pool-name="MyAppDS"

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                       jndi-name="java:app/jdbc/MyApp"

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                       enable="true"/>

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        <jdbc-connection-pool name="MySQLPool"

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                              res-type="javax.sql.XADataSource"

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                              datasource-classname="com.mysql.cj.jdbc.MysqlXADataSource">

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            <property name="url" value="jdbc:h2:mem:hibernateExample"/>

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<property name="User" value="testUser"></property>

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            <property name="Password" value="testPassword"></property>

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            <property name="DatabaseName" value="myapp_db"></property>

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            <property name="ServerName" value="localhost"></property>

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            <property name="PortNumber" value="3306"></property>

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        </jdbc-connection-pool>

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    </resources>

Application Configuration for Relational Database Connections

To use a data source that is configured in your payara-resource.xml file, you can either inject the data source or specify a lookup in your application code. The following examples assume that a jndi-name value of java:app/jdbc/MyApp is specified as the jdbc-resource element attribute in the payara-resource.xml file.

Java

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@Resource(name= "java:app/jdbc/MyApp") 

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DataSource myDB;

Injecting JPA EntityManager Into Your Application

Once your data source is configured in your payara-resource.xml file, we need to register your data source inside the persistence.xml in your src/main/resources/META-INF/persistence.xml file. The jta-data-source is and matches the jndi-name of the data source as specified in the payara-resource.xml.

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    <?xml version="1.0" encoding="UTF-8"?>

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    <persistence version="2.1"

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        xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

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        xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd ">

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        <persistence-unit name="MyAppPU" transaction-type="JTA">

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            <jta-data-source>java:app/jdbc/MyApp</jta-data-source>

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            <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>

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            <properties>

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                <!-- JBoss Wildfly's Hibernate 4 specific JPA properties -->

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                <property name="hibernate.cache.use_second_level_cache" value="true" />

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                <property name="hibernate.hbm2ddl.auto" value="validate" /><!-- NEVER: update -->

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                <property name="hibernate.show_sql" value="false" />

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                <property name="hibernate.format_sql" value="false"/>

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                <property name="hibernate.use_sql_comments" value="false" />

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                <property name="hibernate.enable_lazy_load_no_trans" value="true"/>

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                <!--  For Performance monitoring on Hibernate -->

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                <property name="hibernate.generate_statistics" value="false"/>

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                <property name="hibernate.cache.use_structured_entries" value="false"/>

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                <!-- TomEE PluME 1.7.2 and higher with EclipseLink  -->

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                <property name="eclipselink.logging.logger" value="JavaLogger" />

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            </properties>

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        </persistence-unit>

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    </persistence>

You can inject your jakarta.persistence.EntityManager in your Java application code by specifying your persistence unit MyAppPU in your PersistenceContext annotation:

Java

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@PersistenceContext(unitName="MyAppPU")

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private EntityManager entityManager;

With that, you can get your Java microservice application to connect and interact with a relational database through the Jakarta Persistence API!