While performing relational database management tasks using Java, one major issue that crops up is the type of data. Java objects usually contain non-scalar values, whereas most popular database systems only accept scalar values such as strings and integers. To resolve this issue, programmers can either choose to only accept scalar values within the program or convert the accepted non-scalar values into simpler scalar values when writing into the database.
The second type of data manipulation (data entry/data retrieval) is known as object-relational mapping (ORM). Herein figures one widely adopted method of implementing ORM known as the Java Persistence API (JPA). In this article, we will be talking about why and how to implement the Java Persistence API (JPA) while writing a program.
However, before we begin, it is important to note than JPA is just a specification, which means that you cannot implicitly use it while writing a program. There are multiple implementations of JPA such as Apache OpenJPA, Hibernate, and EclipseLink, which can be used depending upon the technology stack, application, and type of function you require within your program.
Why and When Should You Use the Java Persistence API?
Let us take you through a few scenarios where implementing the Java Persistence API can be hugely beneficial.
#1. Works with any Database
If you try to manually write a read/write/access code for a specific database, then the code might not work as intended when tried on a different database. This is because each database maker uses a slightly different structure and dialect within their product. For those who are writing a program that should work the same regardless of the database, JPA can be of great use. Java Persistence API is completely database-independent, and unless you write some purely database-specific code, the JPA can fetch results for all the statements.
#2. Better Performance
JPA makes use of two different caches: first-level cache, and second-level cache. The first-level cache is always active and consists of data related to all the entities accessed within the current transaction. The second-level cache has to be manually activated, and that can be done either for all the entities or for specific ones. All the data available within the second-level cache can be accessed anytime regardless of the current transaction. Therefore, in programs where the same entity data needs to be used multiple times within the same transaction or even within the same program, implementing JPA can be very useful. This is because you will not have to read the same entities, again and again, thus, saving memory and improving the operational time and efficiency.
#3. Resolve Java and Database Data Types Errors
All the data types supported within Java aren’t supported by most relational database products. This creates a lot of issues while trying to read/write data from the storage. While using JPA though, programmers do not have to worry about the data types that are used in the database because the Java Persistence API automatically handles any data type issue between the Java code and the database.
#4. Compatibility with Java SE and Java EE
One major advantage of the Java Persistence API is that it is compatible with both Java SE (Standard Edition) and Java EE (Enterprise Edition). Which means that regardless of whether you are developing a desktop/web/enterprise-level application, you can use JPA without any issues?
#5. JPA Does Not Work Directly on the Database
All the entities stored within the database are read and stored within a persistence class while working with JPA. All the queries while using JPA are written using the Java Persistence Query Language (JPQL), which has a syntax similar to SQL queries, but does operations with the entity data stored within the persistence class objects and not directly on the database entities. Which essentially means that you do not have to worry about accidentally modifying or deleting the values stored within your database entities until you explicitly perform a write operation back to the database?
#6. Multiple Implementations of JPA are Available
As we mentioned in the beginning, JPA itself is just a standard and there are several implementations of the Java Persistence API from multiple developers. Therefore, depending on your requirements and products used, you can choose the JPA implementation that works best. Another advantage of JPA is that it supports both relational and non-relational databases.
Java Persistence API is a vast topic and all its aspects cannot be completely covered in the limited space of this one article. We have, however, tried to include some of the more highlighted features and advantages of using Java Persistence API and hope you will find our take on this informative.
About Author: Sandeep is working as a content marketing executive and guest blogger at Aegis Infoways, Hire Java Spring Boot Developer for java web apps and java programming services.