Book Image

Spring Data

By : Petri Kainulainen
Book Image

Spring Data

By: Petri Kainulainen

Overview of this book

Spring Framework has always had a good support for different data access technologies. However, developers had to use technology-specific APIs, which often led to a situation where a lot of boilerplate code had to be written in order to implement even the simplest operations. Spring Data changed all this. Spring Data makes it easier to implement Spring-powered applications that use cloud-based storage services, NoSQL databases, map-reduce frameworks or relational databases. "Spring Data" is a practical guide that is full of step-by-step instructions and examples which ensure that you can start using the Java Persistence API and Redis in your applications without extra hassle. This book provides a brief introduction to the underlying data storage technologies, gives step-by-step instructions that will help you utilize the discussed technologies in your applications, and provides a solid foundation for expanding your knowledge beyond the concepts described in this book. You will learn an easier way to manage your entities and to create database queries with Spring Data JPA. This book also demonstrates how you can add custom functions to your repositories. You will also learn how to use the Redis key-value store as data storage and to use its other features for enhancing your applications. "Spring Data" includes all the practical instructions and examples that provide you with all the information you need to create JPA repositories with Spring Data JPA and to utilize the performance of Redis in your applications by using Spring Data Redis.
Table of Contents (13 chapters)

Chapter 4. Adding Custom Functionality to JPA Repositories

We have learned how we can manage our entities and create database queries with Spring Data JPA. We have also learned how we can sort and paginate query results. However, if we take a purist architectural point of view, we notice that the described solutions are not following the separation of concerns principle. In fact, our service layer contains code that reveals the inner workings of our repository layer.

This is a trade off between architectural purity and productivity. As always, this choice has some consequences. If we have to migrate our application away from Spring Data JPA, we have to make changes to both the service and repository layer. However, how many times have we heard that the repository layer of an application has to be changed so radically? Exactly. These situations are very rare. Thus, this risk is worth taking when the reward is high.

The techniques described in this chapter can be used to hide the implementation...