Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:
Once the early-adopter seats are all used, the price will go up and stay at $33/year.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, visit the documentation page.
You can also ask questions and leave feedback on the Azure Container Apps GitHub page.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.
And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.
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Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.
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Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
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Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
End-to-end testing is a very useful method to make sure that your application works as intended. This highlights issues in the overall functionality of the software, that the unit and integration test stages may miss.
Playwright is an easy-to-use, but powerful tool that automates end-to-end testing, and supports all modern browsers and platforms.
When coupled with LambdaTest (an AI-powered cloud-based test execution platform) it can be further scaled to run the Playwright scripts in parallel across 3000+ browser and device combinations:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
1. Overview
In this tutorial, we’ll take a look at handling equality with JPA Entity objects.
2. Considerations
In general, equality simply means that two objects are the same. However, in Java, we can change the definition of equality by overriding the Object.equals() and the Object.hashCode() methods. Ultimately, Java allows us to define what it means to be equal. But first, there are a few things we need to consider.
2.1. Collections
Java collections group objects together. The grouping logic uses a special value known as a hash code to determine the group for an object.
If the value returned by the hashCode() method is the same for all entities, this could result in undesired behavior. Let’s say our entity object has a primary key defined as id, but we define our hashCode() method as:
@Override
public int hashCode() {
return 12345;
}
Collections will not be able to distinguish between different objects when comparing them because they will all share the same hash code. Luckily, resolving this is as easy as using a unique key when generating a hash code. For example, we can define the hashCode() method using our id:
@Override
public int hashCode() {
return id * 12345;
}
In this case, we used the id of our entity to define the hash code. Now, collections can compare, sort, and store our entities.
2.2. Transient Entities
Newly created JPA entity objects that have no association with a persistence context are considered to be in the transient state. These objects usually do not have their @Id members populated. Therefore, if equals() or hashCode() use the id in their calculations, this means all transient objects will be equal because their ids will all be null. There are not many cases where this is desirable.
2.3. Subclasses
Subclasses are also a concern when defining equality. It’s common to compare classes in the equals() method. Therefore, including the getClass() method will help to filter out subclasses when comparing objects for equality.
Let’s define an equals() method that will only work if the objects are of the same class and have the same id:
@Override
public boolean equals(Object o) {
if (o == null || this.getClass() != o.getClass()) {
return false;
}
return o.id.equals(this.id);
}
3. Defining Equality
Given these considerations, we have a few choices when handling equality. Accordingly, the approach we take depends on the specifics of how we plan to use our objects. Let’s look at our options.
3.1. No Overrides
By default, Java provides the equals() and hashCode() methods by virtue of all objects descending from the Object class. Therefore, the easiest thing we can do is nothing. Unfortunately, this means that when comparing objects, in order to be considered equal, they have to be the same instances and not two separate instances representing the same object.
3.2. Using a Database Key
In most cases, we’re dealing with JPA entities that are stored in a database. Normally, these entities have a primary key that is a unique value. Therefore, any instances of this entity that have the same primary key value are equal. So, we can override equals() as we did above for subclasses and also override hashCode() using only the primary key in both.
3.3. Using a Business Key
Alternatively, we can use a business key to compare JPA entities. In this case, the object’s key is comprised of members of the entity other than the primary key. This key should make the JPA entity unique. Using a business key gives us the same desired outcome when comparing entities without the need for primary or database-generated keys.
Let’s say we know that an email address is always going to be unique, even if it isn’t the @Id field. We can include the email field in hashCode() and equals() methods:
public class EqualByBusinessKey {
private String email;
@Override
public int hashCode() {
return java.util.Objects.hashCode(email);
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (obj instanceof EqualByBusinessKey) {
if (((EqualByBusinessKey) obj).getEmail().equals(getEmail())) {
return true;
}
}
return false;
}
}
4. Conclusion
In this tutorial, we discussed various ways that we can handle equality when writing JPA entity objects. We also described the considerations we should take when choosing an approach.
The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
