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Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:

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

Partner – Microsoft – NPI EA (cat = Baeldung)
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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.

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

Partner – Orkes – NPI EA (cat=Spring)
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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.

Partner – Orkes – NPI EA (tag=Microservices)
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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.

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 – 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.

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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:

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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 – All Access – NPI EA (cat= Spring)
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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.

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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 – LambdaTest – NPI EA (cat=Testing)
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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:

>> Automated End-to-End Testing With Playwright

Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Course – Spring Sale 2025 – NPI (cat=Baeldung)
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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:

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eBook – Guide Junit – NPI (tag = JUnit)
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Improve your tests with JUnit 5, from mastering the basics to employing the new powerful features from JUnit 5 like extensions, tagging, filtering, parameterized tests, and more:

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1. Overview

In this tutorial, we’ll learn how to mock private fields with Mockito. Mockito is a popular mocking framework often used with JUnit for creating mock objects in Java. It doesn’t inherently support mocking private fields; however, we can use different approaches to mock private fields with Mockito.

Let’s examine a few of them.

2. Project Setup

We’ll start by creating the classes that we’ll use in our examples. We’ll create a class with a private field and a test class to test it.

2.1. Source Classes

First, we’ll create a simple class with a private field:

public class MockService {
    private final Person person = new Person("John Doe");
    
    public String getName() {
        return person.getName();
    }
}

The MockService class has a private field person of type Person. It also has a method, getName(), that returns the name of the person. As we can see, no setter method exists for the person field. So we can’t set the field directly, or change the value of the field.

Now we’ll create the Person class:

public class Person {
    private final String name;
    
    public Person(String name) {
        this.name = name;
    }
    
    public String getName() {
        return name;
    }
}

The Person class has a private field name and a getter method for the field.

2.2. Test Class

Next, we’ll create a test class to test the MockService class:

public class MockServiceUnitTest {
    private Person mockedPerson;

    @BeforeEach
    public void setUp(){
        mockedPerson = mock(Person.class);
    }
}

We create an instance of the Person class and mock it using Mockito. In the next sections, we’ll look at ways to use this mocked instance to replace the private field of the MockService class.

3. Enable Mocking With Java Reflection API

One of the ways to set the private field is to use the Java Reflection API. This is a good method because it doesn’t require any additional dependencies. We can first make the field accessible, and then set the value of the field to the mocked instance.

Let’s look at the code to do this:

@Test
void givenNameChangedWithReflection_whenGetName_thenReturnName() throws Exception {
    Class<?> mockServiceClass = Class.forName("com.baeldung.mockprivate.MockService");
    MockService mockService = (MockService) mockServiceClass.getDeclaredConstructor().newInstance();
    Field field = mockServiceClass.getDeclaredField("person");
    field.setAccessible(true);
    field.set(mockService, mockedPerson);

    when(mockedPerson.getName()).thenReturn("Jane Doe");

    Assertions.assertEquals("Jane Doe", mockService.getName());
}

We use the Class.forName() method to get the class object of the MockService class. Then we create an instance of the MockService class using the getDeclaredConstructor() method.

Next, we use the getDeclaredField() method to get the person field of the MockService class. We make the field accessible using the setAccessible() method, and set the value of the field to the mocked instance using the set() method.

Finally, we can mock the getName() method of the Person class, and test the getName() method of the MockService class to return the mocked value.

4. Enable Mocking With JUnit 5

Similar to Java Reflection API, JUnit 5 also provides utility methods to set private fields. We can use the ReflectionUtils class of JUnit 5 to set a value to the private field:

@Test
void givenNameChangedWithReflectionUtils_whenGetName_thenReturnName() throws Exception {
    MockService mockService = new MockService();
    Field field = ReflectionUtils
      .findFields(MockService.class, f -> f.getName().equals("person"),
        ReflectionUtils.HierarchyTraversalMode.TOP_DOWN)
      .get(0);

    field.setAccessible(true);
    field.set(mockService, mockedPerson);

    when(mockedPerson.getName()).thenReturn("Jane Doe");

    Assertions.assertEquals("Jane Doe", mockService.getName());
}

This method works in the same way as the previous method. The main difference is how we get the field:

  • We use the ReflectionUtils.findFields() method to get the field.
  • It takes the class object of the MockService class and a predicate to find the field. The predicate we use here is to find the field with the name “person.”
  • Additionally, we need to specify the HierarchyTraversalMode. This is important when we have a hierarchy of classes and we want to find the field in the hierarchy.
  • In our case, we have only one class, so we can use any of the TOP_DOWN or BOTTOM_UP modes.

This gives us the field, and we can set the field’s value once again and perform the test.

5. Enable Mocking With Spring Test

If we’re using Spring for our project, Spring Test provides a utility class, ReflectionTestUtils, to set private fields.

5.1. Dependency

Let’s start by adding the Spring Test dependency to our project:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>5.3.25</version>
    <scope>test</scope>
</dependency>

Alternatively, if using Spring Boot, we could use the Spring Boot Starter Test dependency to do the same.

5.2. Test Case

Next, let’s use this class in our test to enable the mocking:

@Test
void givenNameChangedWithReflectionTestUtils_whenGetName_thenReturnName() throws Exception {
    MockService mockService = new MockService();

    ReflectionTestUtils.setField(mockService, "person", mockedPerson);

    when(mockedPerson.getName()).thenReturn("Jane Doe");
    Assertions.assertEquals("Jane Doe", mockService.getName());
}

Here, we use the ReflectionTestUtils.setField() method to set the private field. Internally, this too uses the Java Reflection API to set the field, but removes the need for boilerplate code.

6. Conclusion

In this article, we looked at different ways to mock private fields with Mockito. We explored the Java Reflection API, JUnit 5, and Spring Test to mock private fields.

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.

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

Partner – Orkes – NPI EA (cat = Spring)
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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.

Partner – Orkes – NPI EA (tag = Microservices)
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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.

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:

>> Download the eBook

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:

>> Download the eBook

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:

>> CHECK OUT THE COURSE

Course – Spring Sale 2025 – NPI EA (cat= Baeldung)
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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:

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Course – Spring Sale 2025 – NPI (All)
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Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:

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eBook – Mockito – NPI (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:

>> Download the eBook

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