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:
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:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Regression testing is an important step in the release process, to ensure that new code doesn't break the existing functionality. As the codebase evolves, we want to run these tests frequently to help catch any issues early on.
The best way to ensure these tests run frequently on an automated basis is, of course, to include them in the CI/CD pipeline. This way, the regression tests will execute automatically whenever we commit code to the repository.
In this tutorial, we'll see how to create regression tests using Selenium, and then include them in our pipeline using GitHub Actions:, to be run on the LambdaTest cloud grid:
Get up to speed with the core of Maven quickly, and then go beyond the foundations into the more powerful functionality of the build tool, such as profiles, scopes, multi-module projects and quite a bit more:
1. Overview
This brief tutorial will describe Maven’s <optional> tag and how we can use it to reduce the size and scope of a Maven project’s artifact, such as a WAR, EAR, or JAR.
For a refresher on Maven, check out our comprehensive guide.
2. What Is <optional>?
Sometimes we’ll create a Maven project to be a dependency for other Maven projects. When working on such a project, it may be required to include one or more dependencies that are only useful to a subset of that project’s features.
If an end-user doesn’t use that feature subset, the project still transitively pulls in those dependencies. This bloats the user’s project size unnecessarily, and might even introduce conflicting dependency versions with other project dependencies.
Ideally, we should split the project’s feature subset into its own module and therefore not pollute the rest of the project. However, this is not always practical.
In order to exclude these special dependencies from the main project, we can apply Maven’s <optional> tag to them. This forces any user who wants to use those dependencies to declare them explicitly. However, it does not force those dependencies into a project that doesn’t need them.
3. How to Use <optional>
As we’re going to see we can include the <optional> element with a value of true to make any Maven dependency optional.
Let’s assume we have the following project pom:
<project>
...
<artifactId>project-with-optionals</artifactId>
...
<dependencies>
<dependency>
<groupId>com.baeldung</groupId>
<artifactId>optional-project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<optional>true</optional>
</dependency>
</dependencies>
</project>In this example, although optional-project is labeled as optional, it remains as a usable dependency of project-with-optionals as if the <optional> tag was never there.
In order to see the effect of the <optional> tag, we need to create a new project that depends on project-with-optionals:
<project>
...
<artifactId>main-project</artifactId>
...
<dependencies>
<dependency>
<groupId>com.baeldung</groupId>
<artifactId>project-with-optionals</artifactId>
<version>0.0.1-SNAPSHOT</version>
</dependency>
</dependencies>
</project>Now if we try to reference optional-project from within main-project, we see that optional-project doesn’t exist. This is because the <optional> tag prevents it from being transitively included.
If we find that we need optional-project in our main-project, we simply need to declare it as a dependency.
4. Conclusion
In this article, we looked at Maven’s <optional> tag. The main benefits of using the tag are that it can reduce a project’s size and help prevent version conflicts. We also saw that the tag doesn’t affect the project that uses it.
