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 = 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:

>> Join Pro and download the eBook

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.

Get started with understanding multi-threaded applications with our Java Concurrency guide:

>> Download the eBook

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:

>> Join Pro and download the eBook

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 – 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.

>> GET THE COURSE
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:

>> CHECK OUT THE COURSE

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

>> EXPLORE ACCESS NOW

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:

>> EXPLORE ACCESS NOW

Course – LSS – NPI (cat=Spring Security)
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If you're working on a Spring Security (and especially an OAuth) implementation, definitely have a look at the Learn Spring Security course:

>> LEARN SPRING SECURITY

1. Overview

Security plays a vital role in REST API development. An insecure REST API can provide direct access to sensitive data on back-end systems. So, organizations need to pay attention to API Security. Spring Security provides various mechanisms to secure our REST APIs. One of them is API keys. An API key is a token that a client provides when invoking API calls. In this tutorial, we’ll discuss the implementation of API key-based authentication in Spring Security.

2. REST API Security

Spring Security can be used to secure REST APIs. REST APIs are stateless. Thus, they shouldn’t use sessions or cookies. Instead, these should be secure using Basic authentication, API Keys, JWT, or OAuth2-based tokens.

2.1. Basic Authentication

Basic authentication is a simple authentication scheme. The client sends HTTP requests with the Authorization header that contains the word Basic followed by a space and a Base64-encoded string username:password. Basic authentication is only considered secure with other security mechanisms such as HTTPS/SSL.

2.2. OAuth2

OAuth2 is the de facto standard for REST APIs security. It’s an open authentication and authorization standard that allows resource owners to give clients delegated access to private data via an access token.

2.3. API Keys

Some REST APIs use API keys for authentication. An API key is a token that identifies the API client to the API without referencing an actual user. The token can be sent in the query string or as a request header. Like Basic authentication, it’s possible to hide the key using SSL. In this tutorial, we focus on implementing API Keys authentication using Spring Security.

3. Securing REST APIs with API Keys

In this section, we’ll create a Spring Boot application and secure it using API key-based authentication.

3.1. Maven Dependencies

Let’s start by declaring the spring-boot-starter-security dependency in our pom.xml:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-security</artifactId>
</dependency>

3.2. Creating Custom Filter

The idea is to get the HTTP API Key header from the request and then check the secret with our configuration. In this case, we need to add a custom Filter in the Spring Security configuration class. We’ll start by implementing the GenericFilterBean. The GenericFilterBean is a simple javax.servlet.Filter implementation that is Spring-aware. Let’s create the AuthenticationFilter class:

public class AuthenticationFilter extends GenericFilterBean {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
      throws IOException, ServletException {
        try {
            Authentication authentication = AuthenticationService.getAuthentication((HttpServletRequest) request);
            SecurityContextHolder.getContext().setAuthentication(authentication);
            filterChain.doFilter(request, response);
        } catch (Exception exp) {
            HttpServletResponse httpResponse = (HttpServletResponse) response;
            httpResponse.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
            httpResponse.setContentType(MediaType.APPLICATION_JSON_VALUE);
            PrintWriter writer = httpResponse.getWriter();
            writer.print(exp.getMessage());
            writer.flush();
            writer.close();
        }
    }
}

We only need to implement a doFilter() method. We evaluate the API Key header in this method and set the resulting Authentication object into the current SecurityContext instance. Then, the request is passed to the remaining filters for processing, routed to DispatcherServlet, and finally to our controller. If something goes wrong, we catch the Exception and write back to the caller without going forward with the filter chain. We delegate the evaluation of the API Key and constructing the Authentication object to the AuthenticationService class:

public class AuthenticationService {

    private static final String AUTH_TOKEN_HEADER_NAME = "X-API-KEY";
    private static final String AUTH_TOKEN = "Baeldung";

    public static Authentication getAuthentication(HttpServletRequest request) {
        String apiKey = request.getHeader(AUTH_TOKEN_HEADER_NAME);
        if (apiKey == null || !apiKey.equals(AUTH_TOKEN)) {
            throw new BadCredentialsException("Invalid API Key");
        }

        return new ApiKeyAuthentication(apiKey, AuthorityUtils.NO_AUTHORITIES);
    }
}

Here, we check whether the request contains the API Key header with a secret. If the header is null or isn’t equal to secret, we throw a BadCredentialsException. If the request has the header, it performs the authentication, adds the secret to the security context, and then passes the call to the following security filter. Our getAuthentication method is quite simple – we compare the API Key header and secret with a static value. To construct the Authentication object, we must use the same approach Spring Security typically uses to build the object using standard authentication. So, let’s extend the AbstractAuthenticationToken class and manually trigger authentication.

3.3. Extending AbstractAuthenticationToken

To successfully implement authentication for our application, we need to convert the incoming API Key to an Authentication object such as an AbstractAuthenticationTokenThe AbstractAuthenticationToken class implements the Authentication interface, representing the secret/principal for an authenticated request. Let’s create the ApiKeyAuthentication class:

public class ApiKeyAuthentication extends AbstractAuthenticationToken {
    private final String apiKey;

    public ApiKeyAuthentication(String apiKey, Collection<? extends GrantedAuthority> authorities) {
        super(authorities);
        this.apiKey = apiKey;
        setAuthenticated(true);
    }

    @Override
    public Object getCredentials() {
        return null;
    }

    @Override
    public Object getPrincipal() {
        return apiKey;
    }
}

The ApiKeyAuthentication class is a type of AbstractAuthenticationToken object with the apiKey information obtained from the HTTP request. We use the setAuthenticated(true) method in the construction. As a result, the Authentication object contains apiKey and authenticated fields:

authentication

3.4. Security Config

We can register our custom filter programmatically by creating a SecurityFilterChain bean. In this case, we need to add the AuthenticationFilter before the UsernamePasswordAuthenticationFilter class using the addFilterBefore() method on an HttpSecurity instance. Let’s create the SecurityConfig class:

@Configuration
@EnableWebSecurity
public class SecurityConfig {

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
      http.csrf(AbstractHttpConfigurer::disable)
          .authorizeHttpRequests(authorizationManagerRequestMatcherRegistry -> authorizationManagerRequestMatcherRegistry.requestMatchers("/**").authenticated())
          .httpBasic(Customizer.withDefaults())
          .sessionManagement(httpSecuritySessionManagementConfigurer -> httpSecuritySessionManagementConfigurer.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
          .addFilterBefore(new AuthenticationFilter(), UsernamePasswordAuthenticationFilter.class);
        return http.build();
    }

}

Also, the session policy is set to STATELESS because we’ll use REST endpoints.

3.5. ResourceController

Last, we’ll create the ResourceController with a /home mapping:

@RestController
public class ResourceController {
    @GetMapping("/home")
    public String homeEndpoint() {
        return "Baeldung !";
    }
}

3.6. Disabling the Default Auto-Configuration

We need to discard the security auto-configuration. To do this, we exclude the SecurityAutoConfiguration and UserDetailsServiceAutoConfiguration classes:

@SpringBootApplication(exclude = {SecurityAutoConfiguration.class, UserDetailsServiceAutoConfiguration.class})
public class ApiKeySecretAuthApplication {

    public static void main(String[] args) {
        SpringApplication.run(ApiKeySecretAuthApplication.class, args);
    }
}

Now, the application is ready to test.

4. Testing

We can use the curl command to consume the secured application. First, let’s try to request the /home without providing any security credentials:

curl --location --request GET 'http://localhost:8080/home'

We get back the expected 401 Unauthorized. Now let’s request the same resource, but provide the API Key and secret to access it as well:

curl --location --request GET 'http://localhost:8080/home' \
--header 'X-API-KEY: Baeldung'

As a result, the response from the server is 200 OK.

5. Conclusion

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)
announcement - icon

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)
announcement - icon

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?

Explore the eBook

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:

>> EXPLORE ACCESS NOW

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:

>> EXPLORE ACCESS NOW

Course – LSS – NPI (cat=Security/Spring Security)
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I just announced the new Learn Spring Security course, including the full material focused on the new OAuth2 stack in Spring Security:

>> CHECK OUT THE COURSE

Partner – Microsoft – NPI (cat=Spring)
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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.

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