Java – Page 2 – Natan Code

How to perform database schema versioning with Flyway and Spring?

Flyway is a tool used for database migration control. Migrations are executed automatically, and we also have a history of database modifications. Flyway supports many databases, but in this example, we will use MySQL. Requirements Project With this site, you can create your Spring project: https://start.spring.io To establish a connection with the database, we need…

What is Garbage Collection in Java?

It is a process that manages memory in software written in Java. When running programs on the JVM (Java Virtual Machine), objects are created in the Heap memory. When these objects are no longer needed, the Garbage Collector will find unused objects and remove them from memory, helping to prevent memory leaks. We need to…

How to improve the performance of primitive types in Java’s Stream Api?

Java’s Stream API facilitates code maintenance, is used with lambda expressions and functional paradigm. It offers many features such as filtering a list, among others. Let’s see an example. For this, I created a class called Product. I populated a list of products and created the following stream. My goal is to map the quantity,…

What is Connection Pool?

Connection Pool is very important for improving the response time of applications. To discuss connection pool, it’s important to understand how database connections work in an application. Let’s use the example of a web application, an API. Without Connection Pool A request was made to the application to fetch some information, and in this example,…

How to use Qualifier in Quarkus?

Imagine the following scenario where there are multiple implementations for the same interface, and when using dependency injection, the software needs to understand which implementation to use. Let’s illustrate with an example to understand what the problem is and how to solve it. Website Diagram: https://refactoring.guru/ In the example, we will have a delivery system that…

What is Dependency Injection?

To understand, I believe the best way is through an example. Let’s take a look at a simple delivery system. It’s not a complete system; it’s something didactic and simple to illustrate. Website Diagram: https://refactoring.guru/ In the example, we will have a delivery system that can be done by truck or ship, where there is…

How to create a Custom Annotation in Quarkus Framework?

It’s important to perform validations in the system. There are dependencies available for this with a lot of ready-made solutions. For example, in the case of Quarkus, we can use Hibernate Validator, which provides us with some annotations to solve common problems. However, if it’s necessary to perform a validation for which there is no…

How does the Set interface work in Java?

The Set interface inherits from the Collection interface. There are several implementations of the Set interface, such as HashSet, LinkedHashSet, and TreeSet, each with its own characteristics. Unlike the List interface, we cannot access an element by index in a Set, but it is possible to iterate over the elements. We will see some usage…

How to do a Parameterized Unit Test in Quarkus?

Parameterized unit tests are beneficial for applications as they simplify the process of writing tests, allowing us to run a single test multiple times with different parameters. Requirements I’m using JDK 17, Intellij and Quarkus Version 3.4 on the project. Practice I created this class: These notations represent validations applied to the fields. For instance,…

How does unit test work ? How to do unit test on Quarkus ?

Testing a system is very important to maintain quality. There are some types of tests. Closer to the base of the pyramid, less cost and time are required.Let’s focus on the base of the pyramid. Unit test serves to validate the smallest code units. Generally a system accesses some external service such as a database,…