Spring Boot MCQ Questions – Page 32 of 49

Q: What is the output when accessing `/calculate?num1=10&num2=20`?

A) Sum: 30. Spring automatically performs type conversion for `@RequestParam` values from `String` to the target method parameter type, in this case, `int`.

Q: Given the following Spring Boot controller method and assuming a `redirectTarget.html` template exists, what happens to the `message` attribute when a request is made to `/redirectMe`?

B) The `message` attribute will be lost during the redirect, and trying to access it in `redirectTarget.html` will result in a `NullPointerException` or empty output.. Model attributes added via `Model` are typically for the current request's view. When a `redirect:` prefix is used, a new request is initiated, and the model attributes from the original request are lost. To pass attributes during a redirect, `RedirectAttributes` should be used.

Q: In a typical Spring Boot application using Spring Data JPA, where would you most commonly apply the `@Repository` annotation?

B) On an interface extending `JpaRepository` or `CrudRepository`.. `@Repository` is commonly applied to interfaces or classes that interact directly with the database, often extending Spring Data JPA's `JpaRepository` or `CrudRepository` interfaces for simplified data access.

Q: What is the output when accessing '/users/{id}' if the `id` is invalid (e.g., negative)?

A) Caught by generic handler: User ID cannot be negative. An `@ExceptionHandler` method without a specified exception type (or with `Exception.class`) acts as a catch-all for any exception not handled by more specific handlers. Here, it will catch the `IllegalArgumentException` and return its message.

Q: Given the controller, if `welcome.html` tries to access `${username}` directly, what will be the outcome when navigating to `/welcome`?

B) The page will display nothing or an empty string for `${username}`.. The controller adds an attribute with the name 'user' to the ModelMap. If the Thymeleaf template attempts to access an attribute named 'username', it will not find it in the model. Thymeleaf typically renders an empty string or nothing when an expression resolves to `null` or a missing attribute, rather than throwing a `NullPointerException` directly for missing top-level attributes.

Q: What error will prevent this code from compiling?

A) Compilation error: Attribute 'path' is a duplicate of 'value'.. In Spring's `@RequestMapping` (and its specialized variants), `value` is an alias for `path`. Specifying both attributes with different values (or even the same value) results in a compile-time error because they are considered duplicate attributes.

Q: What is the output when a Spring Boot application attempts to autowire a `@Service` located outside its default component scan base package? (Assume the `@SpringBootApplication` is in `com.example` and `MyHiddenService` is in `com.example.other`.)

B) A Spring exception like NoSuchBeanDefinitionException. Spring Boot's component scan, by default, scans only the package of the main application class and its sub-packages. Since `MyHiddenService` is outside this hierarchy and no explicit `@ComponentScan` is provided, it won't be registered as a bean, leading to a `NoSuchBeanDefinitionException` when autowiring is attempted.

Q: By default, what is the scope of a `@Controller` component when it's managed as a Spring bean in a Spring Boot application?

A) Singleton (one instance per Spring container).. By default, all Spring beans, including `@Controller` components, are created as singletons. This means only one instance of the controller class exists within the Spring application context, serving all incoming requests.

Q: What is the output of this Spring Boot application?

A) App Name: MyWebApp App Version: 1.0. The `@Value` annotation injects properties from the `application.properties` file. `app.name` is found, so 'MyWebApp' is used. `app.version` is not defined in properties, so its default value '1.0' is used.

Q: What is the output of the `System.out.println` statement?

A) PostConstruct. Spring calls methods annotated with `@PostConstruct` after the bean has been constructed and all dependencies have been injected. This happens after the constructor runs, thus 'PostConstruct' is the final status.

Q621 medium code output

What is the output when accessing `/calculate?num1=10&num2=20`?

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);
    }
}

Q622 medium code error

Given the following Spring Boot controller method and assuming a `redirectTarget.html` template exists, what happens to the `message` attribute when a request is made to `/redirectMe`?

java

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

@Controller
public class RedirectController {

    @GetMapping("/redirectMe")
    public String redirectToTarget(Model model) {
        model.addAttribute("message", "Hello from Redirect!");
        return "redirect:/target";
    }

    @GetMapping("/target")
    public String redirectTarget(Model model) {
        // Assume redirectTarget.html tries to access ${message}
        return "redirectTarget";
    }
}

Q623 medium

In a typical Spring Boot application using Spring Data JPA, where would you most commonly apply the `@Repository` annotation?

Q624 medium code output

What is the output when accessing '/users/{id}' if the `id` is invalid (e.g., negative)?

java

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

@RestController
public class UserController {
    @GetMapping("/users/{id}")
    public String getUser(@PathVariable int id) {
        if (id < 0) {
            throw new IllegalArgumentException("User ID cannot be negative");
        }
        return "User " + id + " found.";
    }

    @ExceptionHandler
    public ResponseEntity<String> handleAnyException(Exception ex) {
        return new ResponseEntity<>("Caught by generic handler: " + ex.getMessage(), HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

Q625 medium code error

Given the controller, if `welcome.html` tries to access `${username}` directly, what will be the outcome when navigating to `/welcome`?

java

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

@Controller
public class WelcomeController {

    @GetMapping("/welcome")
    public String showWelcome(ModelMap map) {
        map.addAttribute("user", "Alice");
        return "welcome"; // Assumes welcome.html tries to access ${username}
    }
}

Q626 medium code error

What error will prevent this code from compiling?

java

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyController {

    @RequestMapping(value = "/api/route1", path = "/api/route2")
    public String conflictingPaths() {
        return "This will fail.";
    }
}

Q627 medium code output

What is the output when a Spring Boot application attempts to autowire a `@Service` located outside its default component scan base package? (Assume the `@SpringBootApplication` is in `com.example` and `MyHiddenService` is in `com.example.other`.)

java

import org.springframework.stereotype.Service;

// This class is in package: com.example.other
@Service
class MyHiddenService {
    public String getValue() { return "Hidden Value"; }
}

// In a @SpringBootApplication (base package: com.example) CommandLineRunner, after autowiring:
// @Autowired MyHiddenService service;
// System.out.println(service.getValue());

Q628 medium

By default, what is the scope of a `@Controller` component when it's managed as a Spring bean in a Spring Boot application?

Q629 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.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import org.springframework.context.annotation.PropertySource;

@Component
@PropertySource("classpath:application.properties")
class AppInfo {
    @Value("${app.name:DefaultApp}")
    private String appName;

    @Value("${app.version:1.0}")
    private String appVersion;

    public void printInfo() {
        System.out.println("App Name: " + appName);
        System.out.println("App Version: " + appVersion);
    }
}

// Assuming application.properties contains:
// app.name=MyWebApp

@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        var context = SpringApplication.run(MyApplication.class, args);
        AppInfo appInfo = context.getBean(AppInfo.class);
        appInfo.printInfo();
    }
}

Q630 medium code output

What is the output of the `System.out.println` statement?

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;

@Component class InitOrderComponent {
    private String status = "Initial";
    public InitOrderComponent() { status = "Constructor"; }
    @PostConstruct public void postConstruct() { status = "PostConstruct"; }
    public String getStatus() { return status; }
}

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

Q631 medium

If a Spring Boot controller has `@RequestMapping("/api")` at the class level and a method inside it has `@RequestMapping("/users")`, what is the full path to access this method?

Q632 medium

To automatically validate the data in an object received via `@RequestBody` based on JSR-303 annotations (like `@NotNull`, `@Size`), which additional annotation should be used on the method parameter?

Q633 medium

Can placeholder resolution `${...}` and SpEL `#{...}` be combined within a single `@Value` annotation, and if so, how?

Q634 medium

Which statement best describes the relationship between the InitializingBean interface and the @PostConstruct annotation for bean initialization?

Q635 medium code output

What is the HTTP status code and response body when a GET request is made to `/admin/action` if `UnauthorizedAccessException` is thrown, using the provided Spring Boot classes?

java

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import jakarta.servlet.http.HttpServletRequest;
import java.util.Map;

class UnauthorizedAccessException extends RuntimeException {
    public UnauthorizedAccessException(String message) { super(message); }
}

@RestController
class AdminController {
    @GetMapping("/admin/action")
    public String adminAction() {
        throw new UnauthorizedAccessException("Access denied for this resource");
    }
}

@RestControllerAdvice
class SecurityExceptionHandler {
    @ExceptionHandler(UnauthorizedAccessException.class)
    public ResponseEntity<Map<String, String>> handleUnauthorized(UnauthorizedAccessException ex, HttpServletRequest request) {
        return ResponseEntity.status(HttpStatus.FORBIDDEN)
                             .body(Map.of("error", ex.getMessage(), "path", request.getRequestURI()));
    }
}

Q636 medium code output

What is the output of this code?

java

package com.example;

import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@Repository
class ProductInfoRepository {
    public String getProductDetails() {
        return "Product: Laptop, Price: $1200";
    }
}

@RestController
class ProductController {
    @Autowired ProductInfoRepository repo;
    @GetMapping("/product")
    public String getProduct() {
        return repo.getProductDetails();
    }
}

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);
        // Simulate a web request by directly calling the controller method
        ProductController controller = context.getBean(ProductController.class);
        System.out.println(controller.getProduct());
        context.close();
    }
}

Q637 medium code output

What is the output when accessing `/greet` without the `name` parameter?

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("/greet")
    public String greetUser(@RequestParam String name) {
        return "Hello, " + name + "!";
    }
}

Q638 medium code output

What would be the effect on a request to `/proxy/my-service/hello` with an original `X-Request-ID` header value of `12345`?

java

import org.springframework.cloud.gateway.route.RouteLocator;
import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class GatewayConfig {
    @Bean
    public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
        return builder.routes()
                .route("proxy_route", r -> r.path("/proxy/**")
                        .filters(f -> f.removeRequestHeader("X-Request-ID"))
                        .uri("http://localhost:8087"))
                .build();
    }
}

Q639 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("hasRole('ADMIN')")
    public String getAdminData() { return "Admin Data"; }
}

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.getAdminData()); }
        catch (Exception e) { System.out.println(e.getClass().getSimpleName()); }
    }
}

Q640 medium

To inject the `JAVA_HOME` environment variable using `@Value`, which of the following is the correct syntax?

🌱 Spring Boot MCQ Questions – Page 32