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Accenture Java Spring Boot Interview Questions & Answers

This guide covers real-world technical interview questions asked during an Accenture Java Developer interview. The candidate had exactly 3 years of experience, primarily focused on Java, Spring Boot, REST APIs, and Microservices.

1. Spring Boot & Architecture​

Q: What is your preferred development environment and toolset for a Spring Boot application?​

A: My preferred setup includes STS (Spring Tool Suite) or Eclipse IDE for development, GitLab for version control, and Maven for dependency management.

Q: What are the key advantages of using Spring Boot over traditional Spring applications?​

A: Spring Boot offers significant advantages, including:

  • Auto-Configuration: It automatically configures Spring and third-party libraries based on the dependencies on the classpath.
  • Embedded Servers: It comes with embedded servers like Tomcat, eliminating the need to deploy WAR files to external web servers.
  • Easy Dependency Management: It provides "Starter POMs" which group common dependencies together, preventing version conflicts.
  • Reduced Boilerplate: It heavily reduces the need for verbose XML configurations and repetitive setup code, making development much more efficient than traditional Spring.

Q: Explain the concept of Dependency Injection in Spring and why it's beneficial.​

A: Dependency Injection (DI) is a core feature of the Spring IoC (Inversion of Control) container. Instead of objects creating their own dependencies manually (using the new keyword), the Spring container injects the required objects at runtime. Benefits: It completely decouples the instantiation process, making the code highly modular, loosely coupled, much easier to test (via mocking), and easier to maintain.

Q: What is the role of the @SpringBootApplication annotation?​

A: It is the starting point for any Spring Boot application. It is a convenience annotation that internally combines three critical annotations:

  1. @Configuration: Marks the class as a source of bean definitions.
  2. @EnableAutoConfiguration: Tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings.
  3. @ComponentScan: Tells Spring to look for other components, configurations, and services in the current package and its sub-packages.

Q: How does Spring Boot achieve Auto-Configuration? Can you provide an example?​

A: Spring Boot achieves Auto-Configuration by analyzing the libraries added to the classpath dependencies. It uses @Conditional annotations behind the scenes to guess what beans you might need and wires them up automatically. Example: Data Source Configuration. In traditional Spring, you must explicitly define DataSource beans in XML or Java config. In Spring Boot, if it detects a database driver (like H2 or MySQL) on the classpath, it automatically configures an in-memory or standard database connection pool for you without writing any code.

Q: What are the steps to override a specific Auto-Configuration?​

A: You can override auto-configuration in several ways:

  1. Define a Custom Bean: If you manually define a bean of the same type, Spring Boot will automatically back away and use yours.
  2. Use the exclude attribute: You can explicitly disable an auto-configuration class using the annotation parameter: @SpringBootApplication(exclude = {DataSourceAutoConfiguration.class}).
  3. Property Files: You can modify or override default configuration behaviors by overriding keys in the application.properties or application.yml file.

Q: How would you modify an existing Spring Boot application to convert it into a serverless architecture?​

A: You can convert a Spring Boot application to a serverless architecture by utilizing Spring Cloud Function. This allows you to abstract your business logic into functional interfaces (Function, Consumer, Supplier). You can then integrate this with serverless platforms like AWS Lambda by using the provided Spring Cloud AWS Lambda adapters, eliminating the need for an always-running embedded Tomcat server.

Q: What are Circular Dependencies and how do you address them?​

A: A circular dependency occurs when Class A depends on Class B, and Class B simultaneously depends on Class A. Spring cannot resolve which bean to create first, resulting in an initialization failure (BeanCurrentlyInCreationException). How to address:

  1. The best approach is to redesign the architecture to remove the tight coupling (e.g., extracting shared logic into a third "Class C").
  2. Use Setter Injection instead of Constructor Injection, as Spring can inject the dependency after the object is instantiated.
  3. Use the @Lazy annotation on one of the dependencies so Spring injects a proxy instead of initializing the bean immediately.

2. RESTful APIs & Security​

Q: What annotations are typically used to create RESTful services in Spring Boot?​

A: The primary annotation is @RestController, which combines @Controller and @ResponseBody. Alongside it, you use:

  • @RequestMapping: To define the base URI path at the class level.
  • HTTP Method Annotations: @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping to map specific HTTP operations to controller methods.

Q: How do you test your REST APIs?​

A: I primarily test REST APIs manually using Postman to verify endpoints, payloads, and authorization tokens. (For automated testing, MockMvc and JUnit/Mockito are standard).

Q: How would you handle exceptions in a Spring Boot REST application?​

A: Instead of wrapping every service or controller method in try-catch blocks, the best enterprise strategy is Global Exception Handling. I use the @ControllerAdvice (or @RestControllerAdvice) annotation on a centralized class, and define methods inside it using @ExceptionHandler. This consolidates all error handling into one place, ensuring that the API consistently returns standardized, meaningful JSON error structures and correct HTTP status codes across the entire application.

Q: What approach do you take for securing REST endpoints?​

A: I use Spring Security. Specifically, I implement stateless authentication using JWT (JSON Web Tokens) or OAuth2. By adding the Spring Security dependency, we configure a filter chain that intercepts incoming HTTP requests. The client must pass a valid JWT in the Authorization header. The system validates the token's signature and claims before granting access to the secured REST endpoints.

3. Performance & Scaling​

Q: Describe a Spring Boot project where you significantly improved performance. What techniques did you use?​

A: In a recent project, we noticed specific APIs were being called frequently, causing database bottlenecks. I improved performance using two main techniques:

  1. Caching (Redis): I implemented a Redis cache to store frequently requested, rarely changing data. Instead of hitting the database every time, the application served the data directly from memory, drastically reducing response times.
  2. Asynchronous Processing: For heavy background operations (like sending notifications or updating external systems), I used the @Async annotation. This prevented the main thread from blocking, enhancing overall API throughput.

Q: What is the meaning of asynchronous processing here? How does it help?​

A: Asynchronous processing means executing tasks in the background without forcing the main execution thread to wait for them to finish. For example, if a method needs to call three slow external APIs, an asynchronous approach allows the system to trigger the calls concurrently or pass them to background threads. The main thread immediately continues its work, which prevents bottlenecks and keeps the application highly responsive to user traffic.

Q: If you had to scale a Spring Boot application to handle high traffic, what strategy would you use?​

A: To handle high traffic, I would employ the following strategies:

  • Horizontal Scaling & Load Balancing: Spin up multiple instances of the Spring Boot application and place them behind a Load Balancer (like NGINX or AWS ALB) to distribute incoming traffic evenly.
  • Microservices: Break down monolithic applications into smaller microservices so high-traffic modules can be scaled independently.
  • Caching: Use distributed caching (Redis) to offload read-heavy database queries.
  • Database Replication: Use read-replicas for databases to separate read traffic from write traffic.
  • Asynchronous Processing & Message Queues: Use Kafka or RabbitMQ to decouple heavy background processing from direct user requests.

4. Live Coding​

Q: Write a Java code snippet to swap two numbers without using a temporary variable.​

A: The candidate provided the standard mathematical addition/subtraction approach.

public class SwapNumbers {
    public static void main(String[] args) {
        int a = 5;
        int b = 6;
        
        System.out.println("Before swap: a = " + a + ", b = " + b);
        
        // Swapping logic
        a = a + b;  // a becomes 11
        b = a - b;  // b becomes 11 - 6 = 5
        a = a - b;  // a becomes 11 - 5 = 6
        
        System.out.println("After swap: a = " + a + ", b = " + b);
    }
}