Baeldung Pro – NPI EA (cat = Baeldung)
announcement - icon

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)
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 – 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, 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)
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.

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 – Guide Spring Cloud – NPI EA (cat=Spring Cloud)
announcement - icon

Let's get started with a Microservice Architecture with Spring Cloud:

>> Join Pro and download the eBook

eBook – Mockito – NPI EA (tag = Mockito)
announcement - icon

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 – Java Concurrency – NPI EA (cat=Java Concurrency)
announcement - icon

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)
announcement - icon

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:

>> Join Pro and download the eBook

eBook – Java Streams – NPI EA (cat=Java Streams)
announcement - icon

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)
announcement - icon

Do JSON right with Jackson

Download the E-book

eBook – HTTP Client – NPI EA (cat=Http Client-Side)
announcement - icon

Get the most out of the Apache HTTP Client

Download the E-book

eBook – Maven – NPI EA (cat = Maven)
announcement - icon

Get Started with Apache Maven:

Download the E-book

eBook – Persistence – NPI EA (cat=Persistence)
announcement - icon

Working on getting your persistence layer right with Spring?

Explore the eBook

eBook – RwS – NPI EA (cat=Spring MVC)
announcement - icon

Building a REST API with Spring?

Download the E-book

Course – LS – NPI EA (cat=Jackson)
announcement - icon

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

>> LEARN SPRING
Course – RWSB – NPI EA (cat=REST)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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
eBook – Guide Spring Cloud – NPI (cat=Cloud/Spring Cloud)
announcement - icon

Let's get started with a Microservice Architecture with Spring Cloud:

>> Join Pro and download the eBook

1. Overview

The Spring Cloud Security module provides features related to token-based security in Spring Boot applications.

Specifically, it makes OAuth2-based SSO easier – with support for relaying tokens between Resource Servers, as well as configuring downstream authentication using an embedded Zuul proxy.

In this quick article, we’ll have a look at how we can configure these features using a Spring Boot client application, an Authorization Server and a REST API working as a Resource Server.

Note that for this example, we only have one Client application that uses SSO to demonstrate the cloud security features – but in a typical scenario, we would have at least two client applications to justify the need for Single Sign-On.

2. Quick Start a Cloud Security App

Let’s start by configuring SSO in a Spring Boot application.

First, we need to add the spring-cloud-starter-oauth2 dependency:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-oauth2</artifactId>
    <version>2.2.2.RELEASE</version>
</dependency>

This will also bring in the spring-cloud-starter-security dependency.

We can configure any social site as an Auth Server for our site or we can use our own server. In our case, we’ve chosen the latter option and configured an application that acts as an Authorization Server – which is deployed locally at http://localhost:7070/authserver.

Our authorization server uses JWT tokens.

Additionally, for any Client to be able to retrieve the credentials of a user, we need to configure our Resource Server, running on port 9000, with an endpoint which can serve these credentials.

Here, we’ve configured a /user endpoint that is available at http://localhost:9000/user.

For more details on how to set up an Authorization Server and a Resource Server, check out our previous article here.

We can now add the annotation in a configuration class in our Client application:

@Configuration
public class SiteSecurityConfigurer {
 
    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        // ...   
        http.oauth2Login();    
        // ... 
    }
}

Any requests that require authentication will be redirected to the Authorization Server. For this to work we also have to define the server properties:

spring:
  security:
    oauth2:
      client:
        registration:
          baeldung:
            client-id: authserver
            client-secret: passwordforauthserver
            authorization-grant-type: authorization_code
            redirect-uri: "{baseUrl}/login/oauth2/code/{registrationId}"
        provider:
          baeldung:
            token-uri: http://localhost:7070/authserver/oauth/token
            authorization-uri: http://localhost:7070/authserver/oauth/authorize
            user-info-uri: http://localhost:9000/user

Note that we need to have spring-boot-starter-security in our classpath to find the above configuration working.

3. Relaying Access Tokens

While relaying a token, an OAuth2 Client forwards the OAuth2 token received by it to an outgoing resource request.

Spring Security exposes an OAuth2AuthorizedClientService, which is useful for creating RestTemplate interceptors  Based on this, we can create our own RestTemplate in our client application:

@Bean
public RestOperations restTemplate(OAuth2AuthorizedClientService clientService) {
    return new RestTemplateBuilder().interceptors((ClientHttpRequestInterceptor) 
        (httpRequest, bytes, execution) -> {
        OAuth2AuthenticationToken token = 
        OAuth2AuthenticationToken.class.cast(SecurityContextHolder.getContext()
            .getAuthentication());
        OAuth2AuthorizedClient client = 
            clientService.loadAuthorizedClient(token.getAuthorizedClientRegistrationId(), 
            token.getName());
            httpRequest.getHeaders()
                .add(HttpHeaders.AUTHORIZATION, "Bearer " + client.getAccessToken()
                    .getTokenValue());
        return execution.execute(httpRequest, bytes);
    }).build();
}

Once we’ve configured the bean, the context will forward the access token to the requested services and will also refresh the token if it expires.

4. Relaying an OAuth Token Using the RestTemplate

We previously defined a restOperations bean of type RestTemplate in our Client application. As a result, we can use the getForObject() method of RestTemplate to send a request with the necessary tokens to a protected Resource server from our client.

First, let’s define an endpoint which requires authentication in our Resource Server:

@GetMapping("/person")
@PreAuthorize("hasAnyRole('ADMIN', 'USER')")
public @ResponseBody Person personInfo(){        
    return new Person("abir", "Dhaka", "Bangladesh", 29, "Male");       
}    

This is a simple REST endpoint that returns a JSON representation of a Person object.

Now, we can send a request from the Client application using the getForObject() method which will relay the token to the Resource Server:

@Autowired
private RestOperations restOperations;

@GetMapping("/personInfo")
public ModelAndView person() { 
    ModelAndView mav = new ModelAndView("personinfo");
    String personResourceUrl = "http://localhost:9000/person";
    mav.addObject("person", 
      restOperations.getForObject(personResourceUrl, String.class));       
    
    return mav;
}

5. Configuring Zuul for Token Relay

If we’d like to relay a token downstream to the proxy services, we can use Spring Cloud Zuul Embedded Reverse Proxy.

First, we need to add the Maven dependency for working with Zuul:

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
</dependency>

Next, we need to add the @EnableZuulProxy annotation on to our configuration class in the Client application:

@EnableZuulProxy
@Configuration
public class SiteSecurityConfigurer {
 
    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        // ...   
        http.oauth2Login();    
        // ... 
    }
}

All that’s left to do is add the Zuul configuration properties to our application.yml file:

zuul:
  sensitiveHeaders: Cookie,Set-Cookie  
  routes:
    resource:
      path: /api/**
      url: http://localhost:9000
    user: 
      path: /user/**
      url: http://localhost:9000/user

Any request coming to the /api endpoint of the Client application will be redirected to the Resource Server URL. We also need to provide the URL of the user credentials endpoint.

6. Conclusion

In this quick article, we explored how to use Spring Cloud Security with OAuth2 and Zuul to configure secured authorization and resource servers, as well as how to relay OAuth2 tokens between servers using RestTemplate and Embedded Zuul Proxy.

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)
announcement - icon

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)
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.

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

Working on getting your persistence layer right with Spring?

Explore the eBook

Course – LS – NPI EA (cat=REST)

announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
announcement - icon

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)
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.

eBook Jackson – NPI EA – 3 (cat = Jackson)
eBook – eBook Guide Spring Cloud – NPI (cat=Cloud/Spring Cloud)