Spring Boot MCQ Questions – Page 29 of 49

Q: Which of the following describes the most common use case for `@RequestParam` in a Spring Boot controller?

C) Binding specific query parameters (e.g., `?name=value`) or form data from the request.. `@RequestParam` is primarily used to extract individual query parameters from the URL (e.g., `?param=value`) or parameters from form data submitted with `application/x-www-form-urlencoded` content type.

Q: What is the result when a GET request is made to `/api/process` with the following controller setup?

C) A NullPointerException at runtime when /api/process is accessed. The `myService` field is not properly injected because it's missing the `@Autowired` annotation. This means `myService` will be null, leading to a `NullPointerException` when `myService.doSomething()` is called during a request.

Q: What is the output of this code?

B) Caught exception: NoSuchBeanDefinitionException. The @Repository bean is located in a package (`com.example.repository`) that is not included in the @SpringBootApplication's component scan (`scanBasePackages = "com.example.app"`). As a result, Spring cannot find the bean definition, leading to a NoSuchBeanDefinitionException.

Q: Assume `MyCustomBean` is a simple class with a `getValue()` method. An `@Configuration` class (`AppConfig`) provides a `@Bean` for `MyCustomBean` initialized with "Hello from AppConfig Bean". What does this code print to the console when `testCustomBeanInjection` is executed?

A) Hello from AppConfig Bean. `@SpringBootTest` loads the entire application context, including any `@Configuration` classes and the `@Bean` methods they define. This allows `MyCustomBean` to be autowired and its value retrieved.

Q: What error occurs when accessing `/static/message` with the following controller?

A) org.springframework.web.bind.MissingPathVariableException. The `@PathVariable` `value` is declared in the method signature, but the `@GetMapping` path `/static/message` does not define any path variable. Spring cannot find a value to bind from the URI, resulting in a MissingPathVariableException.

Q: Consider the following service. What error, if any, will occur if this `MyService` is part of a Spring Boot application?

B) The application will start successfully, and MyService will be a Spring bean.. Annotating a `final` class with `@Service` is generally not an issue for basic Spring AOP proxying. Spring uses CGLIB for class-based proxying, which can't extend final classes. However, for simple `@Service` beans without any AOP advice applied, it will still be instantiated successfully as a regular bean.

Q: What is the output printed to the console when the following Spring Boot `@Service` (which is a singleton by default) is used multiple times in a `CommandLineRunner`? (Assume standard Spring Boot application setup and necessary imports.)

A) 2. By default, `@Service` beans are singletons. The same instance of `CounterService` is injected. The `incrementAndGet()` method is called once, then a second time, resulting in the output '2'.

Q: What error will occur during Spring Boot application startup with the following configuration?

B) org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean with name 'nonExistentBean' found.. When a @Bean method has parameters, Spring attempts to resolve these parameters from the application context. By using `@Qualifier("nonExistentBean")`, we explicitly instruct Spring to find a bean with that specific name. Since no such bean is defined or registered, Spring will throw a `NoSuchBeanDefinitionException` during context initialization.

Q: Which of the following injection types are supported by the `@Autowired` annotation?

C) Constructor injection, Setter injection, and Field injection.. `@Autowired` can be applied to fields, setter methods, and constructors to perform dependency injection in Spring-managed beans.

Q: What kind of error will occur when Spring Boot tries to initialize the following services?

B) BeanCurrentlyInCreationException: Requested bean is currently in creation: 'serviceA'.. This code demonstrates a circular dependency between `ServiceA` and `ServiceB` through their constructors. Spring cannot resolve this cycle during bean instantiation and will throw a `BeanCurrentlyInCreationException`.

Q561 medium

Which of the following describes the most common use case for `@RequestParam` in a Spring Boot controller?

Q562 medium code error

What is the result when a GET request is made to `/api/process` with the following controller setup?

java

import org.springframework.web.bind.annotation.*;
import org.springframework.stereotype.Service;

@Service
class MyService { public String doSomething() { return "Processed!"; } }

@RestController
public class MyController {
    private MyService myService; // Missing @Autowired

    @GetMapping("/api/process")
    public String processData() {
        return myService.doSomething();
    }
}

Q563 medium code output

What is the output of this code?

java

package com.example.repository; // Different package

import org.springframework.stereotype.Repository;

@Repository
class ProductRepository {
    public ProductRepository() {
        System.out.println("ProductRepository initialized.");
    }
}

package com.example.app; // Main application package

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;

@SpringBootApplication(scanBasePackages = "com.example.app") // Explicitly scanning wrong package
public class MainApplication {
    public static void main(String[] args) {
        try {
            ConfigurableApplicationContext context = SpringApplication.run(MainApplication.class, args);
            context.getBean(com.example.repository.ProductRepository.class); // Fails here
            context.close();
        } catch (NoSuchBeanDefinitionException e) {
            System.out.println("Caught exception: " + e.getClass().getSimpleName());
        }
    }
}

Q564 medium code output

Assume `MyCustomBean` is a simple class with a `getValue()` method. An `@Configuration` class (`AppConfig`) provides a `@Bean` for `MyCustomBean` initialized with "Hello from AppConfig Bean". What does this code print to the console when `testCustomBeanInjection` is executed?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.junit.jupiter.api.Test;

// MyCustomBean and AppConfig (not shown) with an @Bean method for MyCustomBean.
@SpringBootTest
public class CustomBeanTest {

    @Autowired
    private MyCustomBean myCustomBean;

    @Test
    void testCustomBeanInjection() {
        System.out.println(myCustomBean.getValue());
    }
}

Q565 medium code error

What error occurs when accessing `/static/message` with the following controller?

java

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

@RestController
public class StaticController {
    @GetMapping("/static/message")
    public String getStaticMessage(@PathVariable String value) {
        return "Message: " + value;
    }
}

Q566 medium code error

Consider the following service. What error, if any, will occur if this `MyService` is part of a Spring Boot application?

java

package com.example.app;

import org.springframework.stereotype.Service;

@Service
final class MyService {
    public String getValue() {
        return "Final Service";
    }
}

Q567 medium code output

What is the output printed to the console when the following Spring Boot `@Service` (which is a singleton by default) is used multiple times in a `CommandLineRunner`? (Assume standard Spring Boot application setup and necessary imports.)

java

import org.springframework.stereotype.Service;

@Service
class CounterService {
    private int count = 0;
    public int incrementAndGet() { return ++count; }
}

// In a @SpringBootApplication's CommandLineRunner, after autowiring:
// CounterService counterServiceInstance;
// counterServiceInstance.incrementAndGet();
// System.out.println(counterServiceInstance.incrementAndGet());

Q568 medium code error

What error will occur during Spring Boot application startup with the following configuration?

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.beans.factory.annotation.Qualifier;

public class MyComponent {}

@Configuration
public class AppConfig {
    @Bean
    public MyComponent myComponent(@Qualifier("nonExistentBean") Object param) {
        return new MyComponent();
    }
}

Q569 medium

Which of the following injection types are supported by the `@Autowired` annotation?

Q570 medium code error

What kind of error will occur when Spring Boot tries to initialize the following services?

java

package com.example.app;

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

@Service
class ServiceA {
    private final ServiceB serviceB;

    @Autowired
    public ServiceA(ServiceB serviceB) {
        this.serviceB = serviceB;
    }
}

@Service
class ServiceB {
    private final ServiceA serviceA;

    @Autowired
    public ServiceB(ServiceA serviceA) {
        this.serviceA = serviceA;
    }
}

Q571 medium code output

Given an `AppConfig` with two `String` beans named `profileMessage`, one `@Profile("dev")` returning "Dev Profile Active" and another `@Profile("prod")` returning "Prod Profile Active", what is the output of this test code?

java

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ActiveProfiles;

@SpringBootTest
@ActiveProfiles("dev")
class ActiveProfilesTest {
    @Autowired
    String profileMessage;

    @Test
    void testActiveProfileBean() {
        System.out.print(profileMessage);
    }
}

Q572 medium

Which `@Value` annotation correctly injects the result of the Spring Expression Language (SpEL) expression `10 * 5`?

Q573 medium code output

Given the `spring.profiles.active` property is set to 'dev' (either in `application.properties` or as an environment variable) 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 ProfileInfo {
    @Value("#{'Current profile is: ' + environment['spring.profiles.active']}")
    private String profileMessage;

    public String getProfileMessage() {
        return profileMessage;
    }
}
// In a Spring Boot application, if this component is scanned:
// ProfileInfo info = applicationContext.getBean(ProfileInfo.class);
// System.out.println(info.getProfileMessage());

Q574 medium code error

Consider this Spring Boot controller method. What will happen when it is compiled?

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("/missing-return")
    public ResponseEntity<String> testMethod() {
        String message = "Hello";
        // Missing return statement
    }
}

Q575 medium

Which of the following best describes the idempotency characteristic of a standard HTTP POST request used for resource creation?

Q576 medium code output

What is the output of this Java code if an expired JWT is provided for parsing?

java

import io.jsonwebtoken.*;
import io.jsonwebtoken.security.Keys;
import java.security.Key;
import java.util.Date;

public class JwtParser {
    public static void main(String[] args) {
        Key key = Keys.secretKeyFor(SignatureAlgorithm.HS256);
        // Token generated with expiration set to 1 second in the past
        String expiredJwt = Jwts.builder()
                .setSubject("user123")
                .setExpiration(new Date(System.currentTimeMillis() - 1000L))
                .signWith(key)
                .compact();
        try {
            Jwts.parserBuilder().setSigningKey(key).build().parseClaimsJws(expiredJwt);
            System.out.println("Token is valid");
        } catch (ExpiredJwtException e) {
            System.out.println("ExpiredJwtException caught");
        } catch (Exception e) {
            System.out.println("Other exception: " + e.getClass().getSimpleName());
        }
    }
}

Q577 medium code error

What error will Spring Boot report when starting this application?

java

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

public interface NotificationService { String send(String msg); }

@Service class EmailService implements NotificationService {
    @Override public String send(String msg) { return "Email"; }
}

@Service class SMSService implements NotificationService {
    @Override public String send(String msg) { return "SMS"; }
}

@Component class MessageSender {
    @Autowired private NotificationService notificationService;
}

Q578 medium

What does the generic type parameter `<T>` in `ResponseEntity<T>` primarily represent?

Q579 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.context.annotation.Primary;
import org.springframework.stereotype.Component;

interface Service { String name(); }
@Component @Primary
class PrimaryService implements Service { public String name() { return "Primary"; } }
@Component
class SecondaryService implements Service { public String name() { return "Secondary"; } }

@SpringBootApplication
public class App6 {
    public static void main(String[] args) {
        ApplicationContext ctx = SpringApplication.run(App6.class, args);
        Service service = ctx.getBean(Service.class);
        System.out.println(service.name());
    }
}

Q580 medium

Which Spring MVC annotation is primarily used to bind incoming form data from HTML form fields to a domain object for processing in a controller method?

🌱 Spring Boot MCQ Questions – Page 29