eBook – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
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Let's get started with a Microservice Architecture with Spring Cloud:

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eBook – Mockito – NPI EA (tag = Mockito)
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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:

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eBook – Reactive – NPI EA (cat=Reactive)
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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:

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eBook – Java Streams – NPI EA (cat=Java Streams)
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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:

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eBook – Jackson – NPI EA (cat=Jackson)
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Do JSON right with Jackson

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eBook – HTTP Client – NPI EA (cat=Http Client-Side)
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Get the most out of the Apache HTTP Client

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eBook – Maven – NPI EA (cat = Maven)
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Get Started with Apache Maven:

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eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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eBook – RwS – NPI EA (cat=Spring MVC)
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Building a REST API with Spring?

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Course – LS – NPI EA (cat=Jackson)
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Get started with Spring and Spring Boot, through the Learn Spring course:

>> LEARN SPRING
Course – RWSB – NPI EA (cat=REST)
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Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:

>> The New “REST With Spring Boot”

Course – LSS – NPI EA (cat=Spring Security)
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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:

>> Learn Spring Security

Course – LSD – NPI EA (tag=Spring Data JPA)
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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:

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Partner – Moderne – NPI EA (cat=Spring Boot)
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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.

Course – Spring Sale 2026 – NPI EA (cat= Baeldung)
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Yes, we're now running our Spring Sale. All Courses are 30% off until 31st March, 2026

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Partner – Diagrid – NPI EA (cat= Testing)
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In distributed systems, managing multi-step processes (e.g., validating a driver, calculating fares, notifying users) can be difficult. We need to manage state, scattered retry logic, and maintain context when services fail.

Dapr Workflows solves this via Durable Execution which includes automatic state persistence, replaying workflows after failures and built-in resilience through retries, timeouts and error handling.

In this tutorial, we'll see how to orchestrate a multi-step flow for a ride-hailing application by integrating Dapr Workflows and Spring Boot:

>> Dapr Workflows With PubSub

Course – Spring Sale 2026 – NPI (cat=Baeldung)
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1. Introduction

Spring allows us to attach custom actions to bean creation and destruction. We can, for example, do it by implementing the InitializingBean and DisposableBean interfaces.

In this quick tutorial, we’ll look at a second possibility, the @PostConstruct and @PreDestroy annotations.

Further reading:

Constructor Injection in Spring with Lombok

A quick and practical example of constructor injection with Lombok in Spring

Constructor Dependency Injection in Spring

Quick and practical intro to Constructor based injection with Spring.

Spring @ComponentScan - Filter Types

Explore different types of filter options available with the @ComponentScan annotation.

2. @PostConstruct

Spring calls the methods annotated with @PostConstruct only once, just after the initialization of bean properties. Keep in mind that these methods will run even if there’s nothing to initialize.

The method annotated with @PostConstruct can have any access level, but it can’t be static.

One possible use of @PostConstruct is populating a database. For instance, during development, we might want to create some default users:

@Component
public class DbInit {

    @Autowired
    private UserRepository userRepository;

    @PostConstruct
    private void postConstruct() {
        User admin = new User("admin", "admin password");
        User normalUser = new User("user", "user password");
        userRepository.save(admin, normalUser);
    }
}

The above example will first initialize UserRepository and then run the @PostConstruct method.

3. @PreDestroy

A method annotated with @PreDestroy runs only once, just before Spring removes our bean from the application context.

Same as with @PostConstruct, the methods annotated with @PreDestroy can have any access level, but can’t be static.

@Component
public class UserRepository {

    private DbConnection dbConnection;
    @PreDestroy
    public void preDestroy() {
        dbConnection.close();
    }
}

The purpose of this method should be to release resources or perform other cleanup tasks, such as closing a database connection, before the bean gets destroyed.

4. javax.annotation or jakarta.annotation

From JDK 6 to JDK 8, the @PostConstruct and @PreDestroy annotations were part of the standard Java libraries under the javax.annotation package. However, with JDK 9, the entire javax.annotation package was removed from the core Java modules and fully eliminated in JDK 11. In Jakarta EE 9, this package has been relocated to jakarta.annotation.

So, sometimes, we may ask, “Should I use the annotations from javax.annotation or jakarta annotation?” This depends on the Spring version we use. To quickly understand the compatibilities among Spring, JDK, javax, and jakarta namespaces, let’s summarize them in a table:

Spring Version JDK Version Java / Jakatar Namespace
6.1.x JDK 17 to JDK 23 jakarta
6.0.x JDK 17 to JDK 21 jakarta
5.3.x JDK 8 to JDK 21 javax

As the table above shows, with Spring 6.0.x and 6.1.x, we should use the jakarta namespace. However, if our project uses Spring 5.3.x and JDK 9 or a later version, since Spring 5.3.x only supports the javax namespace, we must explicitly add the javax.annotation-api dependency to our project:

<dependency>
    <groupId>javax.annotation</groupId>
    <artifactId>javax.annotation-api</artifactId>
    <version>1.3.2</version>
</dependency>

The above XML shows an example of adding the javax.annotation-api dependency to a Maven project’s pom.xml.

5. Conclusion

In this brief article, we learned how to use the @PostConstruct and @PreDestroy annotations.

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.
Baeldung Pro – NPI EA (cat = Baeldung)
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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

>> Explore a clean Baeldung

Once the early-adopter seats are all used, the price will go up and stay at $33/year.

eBook – HTTP Client – NPI EA (cat=HTTP Client-Side)
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The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:

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eBook – Java Concurrency – NPI EA (cat=Java Concurrency)
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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:

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eBook – Java Streams – NPI EA (cat=Java Streams)
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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:

>> Join Pro and download the eBook

eBook – Persistence – NPI EA (cat=Persistence)
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Working on getting your persistence layer right with Spring?

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Course – LS – NPI EA (cat=REST)

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Get started with Spring Boot and with core Spring, through the Learn Spring course:

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Partner – Moderne – NPI EA (tag=Refactoring)
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Modern Java teams move fast — but codebases don’t always keep up. Frameworks change, dependencies drift, and tech debt builds until it starts to drag on delivery. OpenRewrite was built to fix that: an open-source refactoring engine that automates repetitive code changes while keeping developer intent intact.

The monthly training series, led by the creators and maintainers of OpenRewrite at Moderne, walks through real-world migrations and modernization patterns. Whether you’re new to recipes or ready to write your own, you’ll learn practical ways to refactor safely and at scale.

If you’ve ever wished refactoring felt as natural — and as fast — as writing code, this is a good place to start.

Course – Spring Sale 2026 – NPI EA (cat= Baeldung)
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Yes, we're now running our Spring Sale. All Courses are 30% off until 31st March, 2026

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Course – Spring Sale 2026 – NPI (All)
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Yes, we're now running our Spring Sale. All Courses are 30% off until 31st March, 2026

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eBook Jackson – NPI EA – 3 (cat = Jackson)