With this blog post, I am going to share what I needed to do to make JPA work in my Jersey 2 Web Services App.
I have created my Jersey 2 app using the following maven snippet:
mvn archetype:generate -DarchetypeGroupId=org.glassfish.jersey.archetypes \
-DarchetypeArtifactId=jersey-quickstart-webapp -DarchetypeVersion=2.26
I then opened pom.xml and added a few new dependencies which I will list below.
POM.XML Dependencies
Open pom.xml file and add the following dependencies:
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-entitymanager -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.2.5.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.2.5.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
</dependency>
My Jersey 2 apps persist data into MySQL, so this is why you see a dependency for MySQL. The complete pom.xml file of my project is below:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.appsdeveloperblog.app.ws</groupId>
<artifactId>mobile-app-ws</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>mobile-app-ws</name>
<build>
<finalName>mobile-app-ws</finalName>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.5.1</version>
<inherited>true</inherited>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey</groupId>
<artifactId>jersey-bom</artifactId>
<version>${jersey.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.glassfish.jersey.containers</groupId>
<artifactId>jersey-container-servlet-core</artifactId>
<!-- use the following artifactId if you don't need servlet 2.x compatibility -->
<!-- artifactId>jersey-container-servlet</artifactId -->
</dependency>
<dependency>
<groupId>org.glassfish.jersey.inject</groupId>
<artifactId>jersey-hk2</artifactId>
</dependency>
<dependency>
<groupId>org.glassfish.jersey.media</groupId>
<artifactId>jersey-media-json-binding</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-beans -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>4.3.7.RELEASE</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-entitymanager -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>4.2.5.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>4.2.5.Final</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
</dependency>
</dependencies>
<properties>
<jersey.version>2.26</jersey.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
</project>
Persistence.xml File
Next, for my JPA to work in Jersey 2 container-deployable web app, I needed to create and add to my project a new file called persistence.xml. Please note that I have replaced the database username, password and the database name with a text you need to replace with actual values.
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
version="2.0">
<persistence-unit name="mysql_persistence_unit" transaction-type="RESOURCE_LOCAL">
<description> Hibernate JPA Configuration Example</description>
<class>com.appsdeveloperblog.com.app.ws.io.entities.UserEntity</class>
<properties>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver" />
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/database_name_here"/>
<property name="javax.persistence.jdbc.user" value="database user name here "/>
<property name="javax.persistence.jdbc.password" value="database user password here"/>
<property name="hibernate.id.new_generator_mappings" value="true"/>
<property name="show_sql" value="true"/>
<property name="hibernate.hbm2ddl.auto" value="update"/>
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
</properties>
</persistence-unit>
</persistence>
Persist Object in MySQL Database with JPA
And finally, to be able to persist Java objects in my Jersey 2 with JPA Web app I needed to create a new Data Access Object or a repository Java class that creates the entity manager using the value I have provided in my persistence.xml file above and then stores the UserEntity Java object in MySQL database.
public class UserRepositoryImpl implements UserRepository {
@Override
public void save(UserEntity userEntity) {
EntityManager entityManager = Persistence.createEntityManagerFactory("mysql_persistence_unit").createEntityManager();
EntityTransaction transaction = entityManager.getTransaction();
try {
transaction.begin();
entityManager.persist(userEntity);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw e;
} finally {
entityManager.clear();
entityManager.close();
}
}
}
Hope this helps you. If you are learning Java Persistence and are actively looking for a good step by step learning materials, check the list of video courses below. One of them might help you out and even much more – Make you a confident developer who can easily build an API with RESTful Web Services using Jersey, Hibernate, and JPA.
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