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.
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.
Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.
With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.
Try a 14-Day Free Trial of Orkes Conductor today.
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.
Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.
With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.
Try a 14-Day Free Trial of Orkes Conductor today.
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.
You can explore the course here:
All Access is finally out, with all of my Spring courses. Learn JUnit is out as well, and Learn Maven is coming fast. And, of course, quite a bit more affordable. Finally.
>> GET THE COURSE
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
The annotation jakarta.persistence.JoinColumn marks a column as a join column for an entity association or an element collection.
In this quick tutorial, we’ll show some examples of basic @JoinColumn usage.
2. @OneToOne Mapping Example
The @JoinColumn annotation combined with a @OneToOne mapping indicates that a given column in the owner entity refers to a primary key in the reference entity:
@Entity
public class Office {
@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "addressId")
private Address address;
}The above code example will create a foreign key linking the Office entity with the primary key from the Address entity. The name of the foreign key column in the Office entity is specified by name property.
3. @OneToMany Mapping Example
When using a @OneToMany mapping, we can use the mappedBy parameter to indicate that the given column is owned by another entity:
@Entity
public class Employee {
@Id
private Long id;
@OneToMany(fetch = FetchType.LAZY, mappedBy = "employee")
private List<Email> emails;
}
@Entity
public class Email {
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "employee_id")
private Employee employee;
}In the above example, Email (the owner entity) has a join column employee_id that stores the id value and has a foreign key to the Employee entity.
4. @JoinColumns
In situations when we want to create multiple join columns, we can use the @JoinColumns annotation:
@Entity
public class Office {
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumns({
@JoinColumn(name="ADDR_ID", referencedColumnName="ID"),
@JoinColumn(name="ADDR_ZIP", referencedColumnName="ZIP")
})
private Address address;
}
The above example will create two foreign keys pointing to ID and ZIP columns in the Address entity:
5. Conclusion
In this article, we learned how to use the @JoinColumn annotation. We looked at how to create both a single-entity association and an element collection.
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.
