Java Persistence API
The Java Persistence API (JPA) is a specification of Java and it is a standard technology. It is used to persist data between Java object and relational database. JPA acts as a bridge between object-oriented domain models and relational database systems. As JPA is just a specification, it doesn't perform any operation by itself. By itself, JPA is not a tool or framework; rather, it defines a set of concepts that can be implemented by any tool or framework. While JPA's object-relational mapping (ORM) model was originally based on Hibernate, it has since evolved.
JPA vs Hibernate
JPA is a standard, while Hibernate is not. In hibernate, we use Session for handling the persistence of data, while in JPA, we use Entity Manager. The query language in Hibernate is Hibernate Query language, while in JPA, the query language is Java Persistence query language. Hibernate is one of the most JPA providers.
Spring Data JPA
Spring Data JPA, part of the larger Spring Data family, makes it easy to easily implement JPA based repositories. This module deals with enhanced support for JPA based data access layers. It makes it easier to build Spring-powered applications that use data access technologies.
It provides the following key dependencies:
- Hibernate: One of the most popular JPA implementations.
- Spring Data JPA: Helps you to implement JPA-based repositories.
- Spring ORM: Core ORM support from the Spring Framework.
Source: https://spring.io/projects/spring-data-jpa
By default Spring uses Hibernate as the default JPA vendor. Although Hibernate is a good choice, some of us may prefer to use EclipseLink as it was supposed to be the reference implementation for the Java Persistence JSR.
How configuring Spring-Boot to use EclipseLink as the JPA provider: https://blog.marcnuri.com/spring-data-jpa-eclipselink-configuring-spring-boot-to-use-eclipselink-as-the-jpa-provider/
Jakarta Persistence
Jakarta Persistence defines a standard for management of persistence and object/relational mapping in Java(R) environments.
Connection Pools
A connection pool is a cache of database connections maintained so that the connections can be reused when future requests to the database are required. Connection pools are used to enhance the performance of executing commands on a database. Opening and maintaining a database connection for each user, especially requests made to a dynamic database-driven website application, is costly and wastes resources. In connection pooling, after a connection is created, it is placed in the pool and it is used again so that a new connection does not have to be established. If all the connections are being used, a new connection is made and is added to the pool. Connection pooling also cuts down on the amount of time a user must wait to establish a connection to the database.
HikariCP
HikariCP is a very lightweight (at roughly 130Kb) and lightning-fast JDBC connection pooling framework developed by Brett Wooldridge around 2012. It is a default in SpringBoot.
HikariCP-benchmark: https://github.com/brettwooldridge/HikariCP-benchmark
Transaction management
Transaction management refers to the tasks of processing multiple transactions issued by various clients of a database server in such a way that the ACID contract can be fulfilled, that is, the properties of atomicity, consistency preservation, isolation, and durability of each individual transaction can be guaranteed. Transaction management is generally understood as requiring serializability-based concurrency control as well as recovery from failures. Concurrency control is the task of scheduling transactions such that their serializability can be guaranteed, while recovery has to restore a consistent database state after a system or media failure. Assuming that the database server is in charge of the “C,” the former guarantees the “I” in ACID, the latter the “A” and “D” properties. Transaction management has to be highly efficient, as modern transaction servers need to accommodate thousands of transactions...
The Spring Framework provides a consistent abstraction for transaction management. The Spring Framework’s declarative transaction management is made possible with Spring aspect-oriented programming (AOP), although, as the transactional aspects code comes with the Spring Framework distribution and may be used in a boilerplate fashion, AOP concepts do not generally have to be understood to make effective use of this code.
Source: https://docs.spring.io/spring-framework/docs/4.2.x/spring-framework-reference/html/transaction.html
Aspect-Oriented Programming
Aspect-Oriented Programming (AOP) complements Object-Oriented Programming (OOP) by providing another way of thinking about program structure. The key unit of modularity in OOP is the class, whereas in AOP the unit of modularity is the aspect. Aspects enable the modularization of concerns such as transaction management that cut across multiple types and objects. (Such concerns are often termed crosscutting concerns in AOP literature.)
One of the key components of Spring is the AOP framework. While the Spring IoC (Inversion of control) container does not depend on AOP, meaning you do not need to use AOP if you don’t want to, AOP complements Spring IoC to provide a very capable middleware solution.
Source: https://docs.spring.io/spring-framework/docs/4.3.15.RELEASE/spring-framework-reference/html/aop.html
Use a Higher-level Database Migration Tool
Spring Boot supports two higher-level migration tools: Flyway and Liquibase.
Example how how to set things up with Liquibase: https://github.com/spring-projects/spring-boot/tree/v2.1.18.RELEASE/spring-boot-samples/spring-boot-sample-liquibase
Policy Framework - Models
Models are implemented using Jakarta Persistence. Spring Data JPA needs same implementation.
import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;
@Entity
@Table(name = "ToscaProperty")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
@Data
@EqualsAndHashCode(callSuper = false)
public class JpaToscaProperty extends PfConcept implements PfAuthorative<ToscaProperty> {
private static final long serialVersionUID = 1675770231921107988L;
@EmbeddedId
@VerifyKey
@NotNull
private PfReferenceKey key;
@Column
@VerifyKey
@NotNull
private PfConceptKey type;
@Column
@NotBlank
private String description;
Spring Repository
Using Spring Data JPA it needs to implement a repository for each model.
@Repository
public interface JpaToscaPropertyRepository extends JpaRepository<JpaToscaProperty, PfReferenceKey> {
}
and also it needs to implement a JUnit test
@ExtendWith(SpringExtension.class)
@DataJpaTest
@Import(value = ParticipantPolicyParameters.class)
@TestPropertySource(locations = {"classpath:application_test.properties"})
class JpaToscaPropertyRepositoryTest {
@Autowired
private JpaToscaPropertyRepository toscaPropertyRepository;
@Test
void test() {
JpaToscaProperty toscaProperty = new JpaToscaProperty();
PfReferenceKey key = toscaProperty.getKey();
Map<String, String> metadata = new HashMap<>();
metadata.put("Key", "Value");
metadata.put("K", "V");
List<JpaToscaConstraint> constraints = new ArrayList<>();
String[] list = new String[] {"First", "Second"};
constraints.add(new JpaToscaConstraintValidValues(Stream.of(list).collect(Collectors.toList())));
toscaProperty.setDefaultValue("DefaultValue");
toscaProperty.setDescription("Description");
toscaProperty.setRequired(true);
toscaProperty.setStatus(ToscaProperty.Status.EXPERIMENTAL);
toscaProperty.setMetadata(metadata);
toscaProperty.setConstraints(constraints);
toscaPropertyRepository.save(toscaProperty);
Optional<JpaToscaProperty> opt = toscaPropertyRepository.findById(key);
assertThat(opt).isNotEmpty();
JpaToscaProperty actual = opt.get();
assertThat(actual.getDefaultValue()).isEqualTo(toscaProperty.getDefaultValue());
assertThat(actual.getDescription()).isEqualTo(toscaProperty.getDescription());
assertThat(actual.isRequired()).isEqualTo(toscaProperty.isRequired());
assertThat(actual.getStatus()).isEqualTo(toscaProperty.getStatus());
assertThat(actual.getType()).isEqualTo(toscaProperty.getType());
assertThat(actual.getConstraints()).isEqualTo(toscaProperty.getConstraints());
}
}
Spring
Example how to convert ControlLoopInstantiationProvider class in Spring style using "@Services" and "@Transactional"
@Service
public class ControlLoopInstantiationProvider {
private final ControlLoopProvider controlLoopProvider;
private final CommissioningProvider commissioningProvider;
/**
* Create a instantiation provider.
*
* @param databaseProviderParameters the parameters for database access
*/
public ControlLoopInstantiationProvider(ControlLoopProvider controlLoopProvider,
CommissioningProvider commissioningProvider) {
this.controlLoopProvider = controlLoopProvider;
this.commissioningProvider = commissioningProvider;
}
@Transactional
public InstantiationResponse createControlLoops(ControlLoops controlLoops) throws PfModelException {
for (ControlLoop controlLoop : controlLoops.getControlLoopList()) {
ControlLoop checkControlLoop = controlLoopProvider.getControlLoop(controlLoop.getKey().asIdentifier());
if (checkControlLoop != null) {
throw new PfModelException(Response.Status.BAD_REQUEST,
controlLoop.getKey().asIdentifier() + " already defined");
}
}
BeanValidationResult validationResult = validateControlLoops(controlLoops);
if (!validationResult.isValid()) {
throw new PfModelException(Response.Status.BAD_REQUEST, validationResult.getResult());
}
controlLoopProvider.createControlLoops(controlLoops.getControlLoopList());
InstantiationResponse response = new InstantiationResponse();
response.setAffectedControlLoops(controlLoops.getControlLoopList().stream()
.map(cl -> cl.getKey().asIdentifier()).collect(Collectors.toList()));
return response;
}
Other links
https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/