Spring Boot MCQ Questions – Page 23 of 49

Q: What is the primary purpose of the `@EnableAutoConfiguration` annotation, which is implicitly included in `@SpringBootApplication`?

B) To automatically configure the Spring application context based on classpath contents, beans, and property settings.. `@EnableAutoConfiguration` is responsible for intelligently adding beans to the application context based on what it finds on the classpath, saving developers from manual configuration.

Q: What is the output when accessing `/calculate?num1=10&num2=invalid`?

B) HTTP Status 400 - Failed to convert value of type 'java.lang.String' to required type 'int'. If the `@RequestParam` value cannot be converted to the target method parameter type (e.g., 'invalid' to `int`), Spring throws a `MethodArgumentTypeMismatchException`, resulting in an HTTP 400 Bad Request error.

Q: How can a Spring Boot controller method receive multiple values for a single request parameter name (e.g., `colors=red&colors=blue`)?

B) By defining the method argument as a `String[]` or `List `.. Spring Boot can automatically bind multiple values for the same request parameter name to an array (e.g., `String[]`) or a `List` (e.g., `List `) as the method argument type.

Q: What is the printed output of this code?

A) Named Component. The `@Component` annotation allows specifying a custom bean name. When retrieving the bean, `context.getBean("myCustomBeanName", NamedComponent.class)` successfully fetches the bean using its explicit name.

Q: Which component of `@SpringBootApplication` is primarily responsible for ensuring that `@Service`, `@Repository`, and `@Controller` annotated classes are found and registered as beans?

C) `@ComponentScan`. `@ComponentScan` is explicitly designed to discover and register Spring components (like `@Service`, `@Repository`, `@Controller`, `@Component`) within the defined scan paths.

Q: To retrieve a value from the URL's query string (e.g., `GET /items?name=laptop`) using `@RequestMapping`, which parameter annotation would typically be used in the method signature?

C) @RequestParam. `@RequestParam` is used to bind web request parameters (from the query string or form data) to a method parameter, making it suitable for handling parameters like `name=laptop`.

Q: To ensure a handler method only processes requests that include a specific HTTP header (e.g., `X-API-Version=1`), which attribute of `@RequestMapping` would you use?

B) headers. The `headers` attribute allows you to map a request based on the presence, absence, or specific value of an HTTP request header, like `headers = "X-API-Version=1"`.

Q: If a client sends a plain text body like "MyReport" with `Content-Type: text/plain` to this endpoint, what will be the HTTP error returned by Spring Boot?

A) HTTP 415 Unsupported Media Type.. When `@RequestBody` is used, Spring's message converters expect a specific `Content-Type` (e.g., `application/json`). If the client sends a different content type like `text/plain`, no suitable converter can be found, leading to an HTTP 415 Unsupported Media Type error.

Q: What will be printed when this Spring Boot application runs?

A) Hello, Spring Boot!. The `@Qualifier("welcomeMsg")` annotation on the `message` field explicitly requests the `String` bean that has been qualified with 'welcomeMsg', which is 'Hello, Spring Boot!'.

Q: What error will occur when the Spring context initializes `MyClient`?

A) org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'ExternalApiConnector' available. ExternalApiConnector is a regular class and not a Spring-managed component. Spring's dependency injection container will not find a bean of this type to inject into MyClient, resulting in a NoSuchBeanDefinitionException.

Q441 medium

What is the primary purpose of the `@EnableAutoConfiguration` annotation, which is implicitly included in `@SpringBootApplication`?

Q442 medium code output

What is the output when accessing `/calculate?num1=10&num2=invalid`?

java

import org.springframework.web.bind.annotation.*;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RestController
public class MyApp {
    public static void main(String[] args) {
        SpringApplication.run(MyApp.class, args);
    }

    @GetMapping("/calculate")
    public String calculate(@RequestParam int num1, @RequestParam int num2) {
        return "Sum: " + (num1 + num2);
    }
}

Q443 medium

How can a Spring Boot controller method receive multiple values for a single request parameter name (e.g., `colors=red&colors=blue`)?

Q444 medium code output

What is the printed output of this code?

java

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

@Component("myCustomBeanName") // Explicit bean name
class NamedComponent {
    public String getName() { return "Named Component"; }
}

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        var context = SpringApplication.run(DemoApplication.class, args);
        var component = context.getBean("myCustomBeanName", NamedComponent.class);
        System.out.println(component.getName());
    }
}

Q445 medium

Which component of `@SpringBootApplication` is primarily responsible for ensuring that `@Service`, `@Repository`, and `@Controller` annotated classes are found and registered as beans?

Q446 medium

To retrieve a value from the URL's query string (e.g., `GET /items?name=laptop`) using `@RequestMapping`, which parameter annotation would typically be used in the method signature?

Q447 medium

To ensure a handler method only processes requests that include a specific HTTP header (e.g., `X-API-Version=1`), which attribute of `@RequestMapping` would you use?

Q448 medium code error

If a client sends a plain text body like "MyReport" with `Content-Type: text/plain` to this endpoint, what will be the HTTP error returned by Spring Boot?

java

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

@RestController
@RequestMapping("/reports")
public class ReportController {
    @PostMapping
    public String generateReport(@RequestBody ReportData data) {
        return "Report generated for type: " + data.getType();
    }
}

class ReportData {
    private String type;
    public String getType() { return type; }
    public void setType(String type) { this.type = type; }
}

Q449 medium code output

What will be printed when this Spring Boot application runs?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;

@Configuration
class StringConfig {
    @Bean
    @Qualifier("welcomeMsg")
    public String greeting() { return "Hello, Spring Boot!"; }

    @Bean
    @Qualifier("farewellMsg")
    public String goodbye() { return "Goodbye, Spring Boot!"; }
}

@Component
class StringPrinter implements CommandLineRunner {
    @Autowired
    @Qualifier("welcomeMsg")
    private String message;

    @Override
    public void run(String... args) { System.out.println(message); }
}

@SpringBootApplication
class App {}

Q450 medium code error

What error will occur when the Spring context initializes `MyClient`?

java

import org.springframework.stereotype.Component;

class ExternalApiConnector {
    public ExternalApiConnector() {}
    public void connect() { System.out.println("Connecting..."); }
}

@Component
public class MyClient {
    private final ExternalApiConnector connector;
    public MyClient(ExternalApiConnector connector) {
        this.connector = connector;
    }
}

Q451 medium code output

Assume there is a `ConfigComponent` class that injects a property `@Value("${app.message:Default Message}")`. What does this code print to the console when `testPropertyOverride` is executed?

java

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

// ConfigComponent (not shown) injects @Value("${app.message:Default Message}")
@SpringBootTest(properties = {"app.message=Test Override Message"})
public class PropertyOverrideTest {

    @Autowired
    private ConfigComponent configComponent;

    @Test
    void testPropertyOverride() {
        System.out.println(configComponent.getMessage());
    }
}

Q452 medium code error

Given the following Spring Boot controller method for displaying a form and a Thymeleaf template (`productForm.html`) that uses `th:object="${productForm}"`, what error will occur when `/showProductForm` is accessed?

java

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;

public class ProductForm {
    private String name;
    private double price;
    // Getters and Setters, default constructor...
}

@Controller
public class ProductController {
    @GetMapping("/showProductForm")
    public String showProductForm() {
        return "productForm";
    }
}

Q453 medium code output

Given the `EventDto` and controller, what is the return value of `createEvent` if the POST request body is `{"title":"Meeting", "eventTime":"2024-07-20T10:30:00"}`?

java

import org.springframework.web.bind.annotation.*;
import lombok.Data;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;

@Data
class EventDto {
    private String title;
    private LocalDateTime eventTime;
}

@RestController
@RequestMapping("/events")
public class EventController {

    @PostMapping
    public String createEvent(@RequestBody EventDto eventDto) {
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
        return "Event: " + eventDto.getTitle() + " at " + eventDto.getEventTime().format(formatter);
    }
}

Q454 medium code error

What error will occur when compiling the following Spring Boot code?

java

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;

public class ResponseBuilderTest {
    public ResponseEntity<String> createResponse() {
        return ResponseEntity.status(HttpStatus.OK).header("X-Custom", "value").build("Body Content");
    }
}

Q455 medium code error

What error occurs during Spring Boot application startup?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.Optional;

interface MyDependency {}

@Component
class MyDependencyImplA implements MyDependency {}

@Component
class MyDependencyImplB implements MyDependency {}

@Component
class MyConsumer {
    @Autowired(required = false)
    private MyDependency dependency;
}

Q456 medium

How can a specific HTTP request header (e.g., `User-Agent` or `Authorization`) be accessed and bound to a method parameter in a Spring Boot GET controller method?

Q457 medium code error

What error will occur during application startup for the following component and configuration?

java

java
@Component
public class NetworkConfig {
    @Value("${network.port:invalid}")
    private int port;

    public int getPort() {
        return port;
    }
}


properties
# application.properties (file does NOT contain 'network.port')

Q458 medium

How would you add a custom header named 'X-Request-ID' with the value '12345' to a `ResponseEntity` that returns an HTTP 200 OK status with data?

Q459 medium code output

What is the output of this Spring Boot application?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@SpringBootApplication
public class MyApp {
    public static void main(String[] args) {
        ApplicationContext context = SpringApplication.run(MyApp.class, args);
        MessageService service = context.getBean(MessageService.class);
        System.out.println(service.getMessage());
    }
}

interface MessageService { String getMessage(); }

class EmailService implements MessageService {
    @Override
    public String getMessage() { return "Sending email..."; }
}

@Configuration
class AppConfig {
    @Bean
    public MessageService emailService() { // Returns interface type
        return new EmailService();
    }
}

Q460 medium code output

What is the console output when a GET request is made to `/error` in this setup?

java

import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@Component
class ErrorInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        System.out.println("ErrorInterceptor: preHandle");
        return true;
    }
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) { /* Not called if exception occurs */ }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        System.out.println("ErrorInterceptor: afterCompletion - Exception: " + (ex != null ? ex.getMessage() : "None"));
    }
}

@Configuration
class ErrorWebConfig implements WebMvcConfigurer {
    private final ErrorInterceptor interceptor;
    public ErrorWebConfig(ErrorInterceptor interceptor) { this.interceptor = interceptor; }
    @Override
    public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(interceptor).addPathPatterns("/error"); }
}

@RestController
class ErrorController {
    @GetMapping("/error")
    public String simulateError() {
        System.out.println("Controller: Throwing exception");
        throw new RuntimeException("Simulated error");
    }
}

🌱 Spring Boot MCQ Questions – Page 23