Spring Boot MCQ Questions – 971 Practice Questions

Q: What is the HTTP status code and response body returned by this Spring Boot controller method?

C) Status: 418 I'm a Teapot, Body: "I am a teapot!". ResponseEntity.status(HttpStatus.IM_A_TEAPOT).body() sets the HTTP status code to 418, which corresponds to the humorous 'I'm a Teapot' status, along with the specified body.

Q: What is the output of this code?

A) User Profile. The `getUserProfile` method requires the `ROLE_USER` authority. The authenticated user correctly possesses this authority, so the method executes successfully.

Q: When a client successfully deletes an employee using this endpoint, what HTTP status code will be returned, and why is this problematic?

A) 200 OK, which is problematic because a DELETE operation should typically return 204 No Content or 202 Accepted.. The endpoint explicitly returns `ResponseEntity.ok().build()`, resulting in an HTTP 200 OK status code. While the deletion is successful, REST best practices recommend 204 No Content for successful deletions with no response body, or 202 Accepted if asynchronous.

Q: The following Spring Boot application attempts to use a data access class. What error will occur when the application context tries to load and `ProductService` is created?

A) org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.example.dao.ProductRepositoryImpl' available.. The `ProductRepositoryImpl` class is missing the `@Repository` (or `@Component`) annotation. Therefore, Spring's component scanning will not detect it as a bean, and `ProductService` will fail to inject it, resulting in a `NoSuchBeanDefinitionException`.

Q: What is the output of this code?

A) Hello ApplicationContext!. The `@SpringBootApplication` scans for components, registering `MyService` as a bean. The `ApplicationContext` then successfully retrieves and calls the method on this bean.

Q: What error will occur when Spring tries to instantiate `MyService` given the following code?

A) org.springframework.beans.factory.UnsatisfiedDependencyException: No qualifying bean of type 'int' available. Spring expects to find a bean of type `int` to inject into the constructor of `MyService`. Since `int` is a primitive and no custom `int` bean is defined, it throws an UnsatisfiedDependencyException.

Q: What does this code print to the console?

A) Router. The JPQL query uses a constructor expression `NEW com.example.ProductInfoDTO(p.name, p.description)` to directly map selected fields into a `ProductInfoDTO` object. It successfully creates the DTO, and then `dto.getProductName()` prints 'Router'.

Q: A Spring Boot application with `@EnableScheduling` uses the following configuration and component. What is the output related to the scheduled task after 10-12 seconds of runtime? `application.properties`: `app.task.rate=3000`

A) Property Based Task executed. Configured Rate: 3000. Counter: 0 Property Based Task executed. Configured Rate: 3000. Counter: 1 Property Based Task executed. Configured Rate: 3000. Counter: 2 Property Based Task executed. Configured Rate: 3000. Counter: 3. The `fixedRateString` attribute allows using property placeholders, which Spring Boot resolves at startup. `app.task.rate` is 3000, so the task runs every 3 seconds. After 10-12 seconds, it will have executed at T=0, T=3, T=6, T=9, making 4 executions. The `@Value` also correctly injects 3000 into `configuredRate`.

Q: Given `application.properties` does NOT contain `app.version` and the following Java code, what does it print?

A) 1.0.0. The @Value annotation supports default values using the ':' operator within the placeholder. If 'app.version' is not found, '1.0.0' is used as the fallback value.

Q: What does this code print?

A) Processing: Data from Service. Spring's component scanning detects `MyDataService` and `MyApplication` (as a `@Component` and `@SpringBootApplication`). The `MyApplication` class uses constructor injection (`@Autowired`) to receive an instance of `MyDataService`. When `process()` is called, it correctly uses the injected service to retrieve the data.

Q1 medium code output

What is the HTTP status code and response body returned by this Spring Boot controller method?

java

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {
    @GetMapping("/teapot")
    public ResponseEntity<String> getTeapot() {
        return ResponseEntity.status(HttpStatus.IM_A_TEAPOT).body("I am a teapot!");
    }
}

Q2 medium code output

What is the output of this code?

java

import org.springframework.security.access.prepost.PreAuthorize;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.core.context.SecurityContextHolder;
import java.util.Collections;

public class SecureService {
    @PreAuthorize("hasAuthority('ROLE_USER')")
    public String getUserProfile() { return "User Profile"; }
}

public class TestRunner {
    public static void main(String[] args) {
        SecurityContextHolder.getContext().setAuthentication(
            new UsernamePasswordAuthenticationToken("user", "pass", Collections.singletonList(new SimpleGrantedAuthority("ROLE_USER")))
        );
        SecureService service = new SecureService();
        try { System.out.println(service.getUserProfile()); }
        catch (Exception e) { System.out.println(e.getClass().getSimpleName()); }
    }
}

Q3 medium code error

When a client successfully deletes an employee using this endpoint, what HTTP status code will be returned, and why is this problematic?

java

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;
import org.springframework.http.HttpStatus;

@RestController
@RequestMapping("/api/employees")
public class EmployeeController {

    private EmployeeService employeeService; // Assume injected

    @DeleteMapping("/{id}")
    public ResponseEntity<Void> deleteEmployee(@PathVariable Long id) {
        employeeService.deleteEmployee(id);
        return ResponseEntity.ok().build(); // Problematic return status
    }
}

Q4 medium code error

The following Spring Boot application attempts to use a data access class. What error will occur when the application context tries to load and `ProductService` is created?

java

package com.example.dao;

public class ProductRepositoryImpl {
    public String findProductById(Long id) {
        return "Product_" + id;
    }
}

package com.example.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.example.dao.ProductRepositoryImpl;

@Service
public class ProductService {
    @Autowired
    private ProductRepositoryImpl productRepository;

    public String getProductDetails(Long id) {
        return productRepository.findProductById(id);
    }
}

// Assuming a @SpringBootApplication main class exists and scans these packages.

Q5 medium code output

What is the output of this code?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

@Component
class MyService { public String message() { return "Hello ApplicationContext!"; } }

@SpringBootApplication
public class App1 {
    public static void main(String[] args) {
        ApplicationContext ctx = SpringApplication.run(App1.class, args);
        MyService service = ctx.getBean(MyService.class);
        System.out.println(service.message());
    }
}

Q6 medium code error

What error will occur when Spring tries to instantiate `MyService` given the following code?

java

import org.springframework.stereotype.Component;

@Component
public class MyService {
    private final int value;

    public MyService(int value) {
        this.value = value;
    }
}

Q7 medium code output

What does this code print to the console?

java

package com.example;

import jakarta.persistence.*;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;

@Entity
public class Product {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String description;

    public Product() {}
    public Product(Long id, String name, String description) { this.id = id; this.name = name; this.description = description; }
    public String getName() { return name; }
    public String getDescription() { return description; }
}

class ProductInfoDTO {
    private String productName;
    private String productDescription;
    public ProductInfoDTO(String productName, String productDescription) {
        this.productName = productName;
        this.productDescription = productDescription;
    }
    public String getProductName() { return productName; }
    public String getProductDescription() { return productDescription; }
}

interface ProductRepository extends JpaRepository<Product, Long> {
    @Query("SELECT NEW com.example.ProductInfoDTO(p.name, p.description) FROM Product p WHERE p.id = :id")
    ProductInfoDTO findProductInfoByIdJPQL(@Param("id") Long id);
}

// Assume ProductRepository is autowired as 'productRepository'
// And the database contains: Product(id=1, name='Router', description='Wireless AC Router')
ProductInfoDTO dto = productRepository.findProductInfoByIdJPQL(1L);
System.out.println(dto.getProductName());

Q8 medium code output

A Spring Boot application with `@EnableScheduling` uses the following configuration and component. What is the output related to the scheduled task after 10-12 seconds of runtime? `application.properties`: `app.task.rate=3000`

java

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
import org.springframework.beans.factory.annotation.Value;

@Component
public class PropertyBasedScheduler {

    @Value("${app.task.rate}")
    private long configuredRate;

    private int counter = 0;

    @Scheduled(fixedRateString = "${app.task.rate}")
    public void runPropertyBasedTask() {
        System.out.println("Property Based Task executed. Configured Rate: " + configuredRate + ". Counter: " + counter++);
    }
}

Q9 medium code output

Given `application.properties` does NOT contain `app.version` and the following Java code, what does it print?

java

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class VersionService {
    @Value("${app.version:1.0.0}")
    private String appVersion;

    public String getVersion() {
        return appVersion;
    }
}
// In a Spring Boot application, if this component is scanned:
// VersionService service = applicationContext.getBean(VersionService.class);
// System.out.println(service.getVersion());

Q10 medium code output

What does this code print?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;

@Service static class MyDataService { public String getData() { return "Data from Service"; } }

@Component
@SpringBootApplication
public class MyApplication {
    private final MyDataService dataService;
    @Autowired public MyApplication(MyDataService dataService) { this.dataService = dataService; }
    public String process() { return "Processing: " + dataService.getData(); }
    public static void main(String[] args) {
        MyApplication app = SpringApplication.run(MyApplication.class, args).getBean(MyApplication.class);
        System.out.println(app.process());
    }
}

Q11 medium code output

What does this code print?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@SpringBootApplication
public class MyApplication {
    @Bean @ConditionalOnProperty(name = "feature.enabled", havingValue = "true")
    public String myConditionalBean() { return "Conditional Bean Created"; }

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(MyApplication.class);
        app.setDefaultProperties(java.util.Collections.singletonMap("feature.enabled", "true"));
        ConfigurableApplicationContext ctx = app.run(args);
        try { System.out.println(ctx.getBean("myConditionalBean", String.class)); }
        catch (org.springframework.beans.factory.NoSuchBeanDefinitionException e) { System.out.println("Conditional Bean NOT Created"); }
    }
}

Q12 medium

What is the consequence if you declare an `@RequestParam(required = false)` for a primitive type (e.g., `int`) and the parameter is missing in the request?

Q13 medium

How can you enable automatic validation for an object bound with `@RequestBody` in a Spring Boot controller method?

Q14 medium

Which of the following annotations is used within a `@RestController` method to bind the incoming HTTP request body to a method parameter?

Q15 medium code error

What error prevents this Spring Boot application from starting successfully?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class MyComponent {

    @Autowired
    private static String appName; // Static fields cannot be autowired

    public void displayAppName() {
        System.out.println("Application Name: " + appName);
    }
}

Q16 medium code output

What is the output of this code when `App` is executed?

java

import javax.annotation.PostConstruct;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Component;

@Component
class MyBean {
    public MyBean() { System.out.println("1. MyBean Constructor"); }
    @PostConstruct public void init() { System.out.println("2. MyBean @PostConstruct"); }
}
@ComponentScan
public class App {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class);
        context.close();
    }
}

Q17 medium code error

What is the expected error when a client sends a GET request to /api/items without a Content-Type header?

java

import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api")
public class ItemService {

    @GetMapping(value = "/items", consumes = MediaType.APPLICATION_JSON_VALUE)
    public String getItems() {
        return "Items list";
    }
}

Q18 medium code output

What will be the exact path (including the query parameter) that the browser is redirected to after the `saveData` method is called with a POST request?

java

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;

@Controller
public class RedirectController {
    @PostMapping("/data/save")
    public String saveData(RedirectAttributes redirectAttributes) {
        redirectAttributes.addAttribute("status", "success");
        redirectAttributes.addFlashAttribute("message", "Data saved successfully!");
        return "redirect:/status";
    }
}

Q19 medium code output

What is the output of this code snippet, assuming there are 2 `Product` entities with `category="Electronics"` and the `deleteByCategory` method is called within a Spring-managed transaction?

java

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.transaction.annotation.Transactional;

interface ProductRepository extends JpaRepository<Product, Long> {
    @Transactional
    Long deleteByCategory(String category);
}

// Assuming Product and ProductRepository are properly defined and wired
// and 'productRepository' is an injected instance.
// Simulate DB content: Product(id=1, name='TV', category='Electronics')
//                     Product(id=2, name='Phone', category='Electronics')
//                     Product(id=3, name='Book', category='Books')

public class TestService {
    ProductRepository productRepository;

    public TestService(ProductRepository productRepository) {
        this.productRepository = productRepository;
    }

    public Long performDelete() {
        return productRepository.deleteByCategory("Electronics");
    }
}
// In a conceptual main method or test:
// System.out.println(new TestService(productRepositoryMock).performDelete());

Q20 medium

Which annotation is primarily used in Spring Boot to automatically inject dependencies into a class field, constructor, or setter method, embodying IoC?

🌱 Spring Boot MCQ Questions