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.
Distributed systems often come with complex challenges such as service-to-service communication, state management, asynchronous messaging, security, and more.
Dapr (Distributed Application Runtime) provides a set of APIs and building blocks to address these challenges, abstracting away infrastructure so we can focus on business logic.
In this tutorial, we'll focus on Dapr's pub/sub API for message brokering. Using its Spring Boot integration, we'll simplify the creation of a loosely coupled, portable, and easily testable pub/sub messaging system:
1. Overview
Spring Data MongoDB module improves readability and usability when interacting with a MongoDB database in Spring projects.
In this tutorial, we’ll focus on how to handle the ZonedDateTime Java objects when reading and writing into a MongoDB database.
2. Setup
To work with Spring Data MongoDB module, we need to add the following dependency:
<dependency>
<groupId>org.springframework.data</groupId>
<artifactId>spring-data-mongodb</artifactId>
<version>3.4.7</version>
</dependency>The latest version of the library can be found here.
Let’s define a model class called Action (with a ZonedDateTime attribute):
@Document
public class Action {
@Id
private String id;
private String description;
private ZonedDateTime time;
// constructor, getters and setters
}To interact with the MongoDB, we’ll also create an interface that extends the MongoRepository:
public interface ActionRepository extends MongoRepository<Action, String> { }Now we’ll define a test that will insert an Action object into a MongoDB and assert that it was stored with the correct time. In the assert evaluation, we’re removing the nanoseconds information since the MongoDB Date type has a precision of milliseconds:
@Test
public void givenSavedAction_TimeIsRetrievedCorrectly() {
String id = "testId";
ZonedDateTime now = ZonedDateTime.now(ZoneOffset.UTC);
actionRepository.save(new Action(id, "click-action", now));
Action savedAction = actionRepository.findById(id).get();
Assert.assertEquals(now.withNano(0), savedAction.getTime().withNano(0));
}Out of the box, we will get the following error when running our test:
org.bson.codecs.configuration.CodecConfigurationException:
Can't find a codec for class java.time.ZonedDateTimeSpring Data MongoDB has no ZonedDateTime converters defined. Let’s see how we can configure them.
3. The MongoDB Converters
We can handle ZonedDateTime objects (across all models) by defining a converter for reading from a MongoDB and one for writing into it.
For reading, we’re converting from a Date object into a ZonedDateTime object. In the next example, we use the ZoneOffset.UTC since Date object does not store zone information:
public class ZonedDateTimeReadConverter implements Converter<Date, ZonedDateTime> {
@Override
public ZonedDateTime convert(Date date) {
return date.toInstant().atZone(ZoneOffset.UTC);
}
}Then, we’re converting from a ZonedDateTime object into a Date object. We can add the zone information to another field if needed:
public class ZonedDateTimeWriteConverter implements Converter<ZonedDateTime, Date> {
@Override
public Date convert(ZonedDateTime zonedDateTime) {
return Date.from(zonedDateTime.toInstant());
}
}Since Date objects do not store a zone offset, we use UTC in our examples. With the ZonedDateTimeReadConverter and the ZonedDateTimeWriteConverter added to the MongoCustomConversions, our test will now pass.
A simple printing of the stored object will look like this:
Action{id='testId', description='click', time=2018-11-08T08:03:11.257Z}To learn more about how to register MongoDB converters, we can refer to this tutorial.
4. Conclusions
In this quick article, we saw how to create MongoDB converters in order to handle Java ZonedDateTime objects.
