Welcome!

Java IoT Authors: Pat Romanski, Elizabeth White, Liz McMillan, Yeshim Deniz, Mehdi Daoudi

Related Topics: Java IoT

Java IoT: Article

Java Feature — Using the Java Persistence API (JPA) with Spring 2.0

How to use JPA in new or existing Spring applications to achieve standardized persistence

The EJB 3.0 Java Persistence API (JPA) was released in May 2006 as part of the Java Enterprise Edition 5 (Java EE) platform, and it has already garnered a great deal of attention and praise. What began as merely an easier-to-use successor to the much-maligned container-managed persistence (CMP) portion of the EJB component standard soon evolved into a full-blown incorporation of the existing best practices of the most prominent and popular object-relational (O-R) persistence products in use. The result is that applications now have a modern standard for lightweight enterprise Java persistence that they can use in any compliant Java EE 5 application server, or in Java Standard Edition (SE) applications.

The Spring application framework has been in existence for four years, and it has become a popular choice both in an application server context and standalone. Like JPA, Spring is a technology designed to allow applications to be built from POJOs. The Spring Framework runs within whatever runtime context an application requires, and it supports applications by providing a wide range of services. Some of these services are abstractions over existing container-level services, whereas others add value to the Java EE container. The persistence access layer, which is particularly popular with the Spring community, is nicely integrated with whatever persistence runtime is being used and facilitates a sound testable architectural approach to working with persistent objects. Spring 1.x included support for a variety of open source and commercial persistence implementations such as TopLink, Hibernate, iBATIS, and JDO, as well as the standard Java database connectivity (JDBC) API that's part of the Java runtime. Spring 2.0 was a major milestone and introduced additional integrated support for JPA. In this article we'll discuss how to use Spring and JPA together and highlight some of the benefits that this architecture can bring to an application.

Spring as a JPA Container
The Java Persistence API was architected so it could be used both inside and outside a Java EE 5 container. When there's no container to manage JPA entity managers and transactions, the application must bear more of the management burden. When running in a JPA container the user experience is more hospitable.

One goal of the JPA specification was to make the technology pluggable. To enable this, the roles of container provider (the container or the side that has control of the runtime threads and transactions), and persistence provider (the provider or the part that implements the persistence API and manages the persistent entities) were defined, and a service provider interface (SPI) binds the two at deployment and runtime. A compliant JPA host container correctly implements this SPI from the container perspective. A compliant JPA persistence provider implements the SPI from the provider perspective. If both sides follow the rules, a compliant container should be able to run any compliant persistence provider implementation, and similarly, a provider should plug into any container.

Although Spring is neither an application server nor a Java EE 5 container, it does enhance, augment, and sometimes implement many of the services used in application servers. Spring 2.0 implements the container portion of the JPA SPI so it can be viewed as a JPA container. As such, it provides the class-loading and weaving support that JPA providers use to help manage the entities at runtime. Users benefit from an environment in which the runtime container and the JPA persistence provider are tightly integrated, but not necessarily in a Java EE 5 context. This provides many of the benefits of Java EE persistence without requiring a Java EE container.

Defining Entities
The most basic part of using JPA is to design and create the entities to be persisted. For the purposes of this article, we will use an extremely simplified library book inventory system with a single entity to illustrate the concepts concretely in Java code.

We'll create a simple Book entity by defining the class and annotating it with an @Entity annotation. The table that stores book instances will default to BOOK, which is exactly what we want. The primary key identifier is the isbn field, so we annotate that field with @Id. Because the title and author fields are basic mappings from the object fields to columns of the same name in the database table, we don't have to do anything to them. We want the genre field to map to a database column named CATEGORY, so we give it a @Column annotation. The resulting Book entity class is shown below.

package org.bookguru;

import javax.persistence.*;
@Entity
public class Book {

    @Id private int isbn;

    private String title;

    private String author;

    @Column(name="CATEGORY")
    private Genre genre;

    // Constructors, getters and setters, etc.
}

Of course a real application would have many entities, but because we want to focus on the use of JPA in Spring, we won't explain how to define and map JPA entities. For more information on defining JPA entities see Pro EJB 3: Java Persistence API.

Using JPA Entities in Spring
The primary way to operate on entities is by using an entity manager. The EntityManager API is the main gateway into JPA and supports basic create/read/update/delete (CRUD) operations. It acts as both a manager of all loaded entities and a factory for queries that enable more entities to be loaded. An entity manager is analogous to an Oracle TopLink session, Hibernate session or an equivalent interface provided by many O-R mapping frameworks.

For example, to create a new persistent entity we would simply create a new Java object of the correct entity type, invoke the persist() method on the entity manager, and pass the new entity as a parameter. Assuming we have access to an entity manager, the code to create a new book is simple.

    Book book = new Book(12769356, "War and Peace", "Leo Tolstoy", Genre.FICTION);
    entityManager.persist(book);

Using JPA and the entity manager in Spring is very simple. In most cases it's simply a matter of annotating a field or method of a Spring bean with @PersistenceContext, which causes an entity manager to be injected. Then invoke the entity manager in the context of a container transaction. Note that @PersistenceContext is a standard JPA annotation and not specific to Spring.


More Stories By Mike Keith

Mike Keith has more than 15 years of teaching, research and practical experience in object-oriented and distributed systems, specializing in object persistence. He was the co-specification lead for EJB 3.0 (JSR 220), a member of the Java EE 5 expert group (JSR 244) and co-authored the premier JPA reference book Pro EJB 3: Java Persistence API. Mike is currently a persistence architect for Oracle and a popular speaker at numerous conferences and events around the world.

More Stories By Rod Johnson

Rod Johnson is the senior vice president of the Application Platform Division at VMware with more than 12 years of technology and management experience. Founder of the Spring Framework, he continues to guide the direction of Spring and is a member of the Java Community Process Executive Committee.

Comments (2)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


IoT & Smart Cities Stories
The platform combines the strengths of Singtel's extensive, intelligent network capabilities with Microsoft's cloud expertise to create a unique solution that sets new standards for IoT applications," said Mr Diomedes Kastanis, Head of IoT at Singtel. "Our solution provides speed, transparency and flexibility, paving the way for a more pervasive use of IoT to accelerate enterprises' digitalisation efforts. AI-powered intelligent connectivity over Microsoft Azure will be the fastest connected pat...
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
Codete accelerates their clients growth through technological expertise and experience. Codite team works with organizations to meet the challenges that digitalization presents. Their clients include digital start-ups as well as established enterprises in the IT industry. To stay competitive in a highly innovative IT industry, strong R&D departments and bold spin-off initiatives is a must. Codete Data Science and Software Architects teams help corporate clients to stay up to date with the mod...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Druva is the global leader in Cloud Data Protection and Management, delivering the industry's first data management-as-a-service solution that aggregates data from endpoints, servers and cloud applications and leverages the public cloud to offer a single pane of glass to enable data protection, governance and intelligence-dramatically increasing the availability and visibility of business critical information, while reducing the risk, cost and complexity of managing and protecting it. Druva's...
BMC has unmatched experience in IT management, supporting 92 of the Forbes Global 100, and earning recognition as an ITSM Gartner Magic Quadrant Leader for five years running. Our solutions offer speed, agility, and efficiency to tackle business challenges in the areas of service management, automation, operations, and the mainframe.
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, compared the Jevons Paradox to modern-day enterprise IT, examin...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
DSR is a supplier of project management, consultancy services and IT solutions that increase effectiveness of a company's operations in the production sector. The company combines in-depth knowledge of international companies with expert knowledge utilising IT tools that support manufacturing and distribution processes. DSR ensures optimization and integration of internal processes which is necessary for companies to grow rapidly. The rapid growth is possible thanks, to specialized services an...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...