Spring Boot MCQ Questions – Page 40 of 49

Q: Consider a class annotated with `@Configuration`. What is the purpose of the `@Bean` annotation within such a class in the context of IoC?

C) It explicitly declares a method to produce a bean that will be managed by the IoC container.. The `@Bean` annotation on a method within a `@Configuration` class indicates that the method produces an object that should be registered as a bean in the Spring IoC container.

Q: What is the output of this code snippet, assuming a `Product` with `id=1` and `name="Laptop"` exists in the database?

A) Laptop. The `findByName` method returns an `Optional `. The `.map(Product::getName)` extracts the name if present, and `.orElse("Product Not Found")` provides a default value if the Optional is empty. Since 'Laptop' exists, its name is returned.

Q: What is the expected output after attempting to save a `Department` with a new `Employee` and subsequently removing that employee from the list when `orphanRemoval` is enabled?

B) Employee Alice status: Removed. The `orphanRemoval = true` attribute on `@OneToMany` specifies that if a child entity (Employee) is disassociated from its parent (Department) within the collection, it should be deleted from the database. Removing `emp1` from `dept.getEmployees()` and saving `dept` will cause `emp1` to be deleted.

Q: What is the default behavior of `@PathVariable` regarding its `required` attribute?

B) It's `true` by default, meaning the path variable must always be present in the URI.. By default, `@PathVariable`s are required. If a URI segment corresponding to a required path variable is missing, the request will typically result in a 404 Not Found error because the path template won't match.

Q: What is the HTTP status and JSON body returned by the `addItem` method when a POST request is made to `/items` with the JSON body `{"name": "Book"}` (Content-Type: application/json)?

A) Status: 200 OK, Body: `{"name": "Book Added"}`. The `@RequestBody Item item` deserializes the JSON into an `Item` object. The `name` property is then modified. The method returns `HttpStatus.OK` (200) along with the modified `Item` object, which is serialized back to JSON.

Q: If a class is annotated with `@Repository` but no specific persistence framework (like JPA or Spring Data JDBC) is configured in the application, what is the effect of the annotation?

B) It will still register the class as a Spring bean (due to `@Component`), but the automatic persistence exception translation aspect will not have significant effect.. `@Repository` inherently provides `@Component` functionality, so the class will be registered as a bean. However, the specific exception translation benefit requires an underlying persistence framework and its integration with Spring's `PersistenceExceptionTranslator`.

Q: What will be the outcome when trying to access the `/data` endpoint of this Spring Boot application if the intention was to return JSON?

D) A 500 Internal Server Error because Spring MVC will attempt to resolve 'myObject' as a view name.. When `@Controller` is used, Spring MVC treats the return value of a method as a view name by default. Since `MyObject` is not a view name, Spring's ViewResolver will fail to resolve it, leading to a 500 Internal Server Error. To return JSON, `@ResponseBody` or `@RestController` should be used.

Q: In Spring MVC, how do you typically instruct the browser to perform a client-side redirect to a different URL from a controller method?

B) By returning a `String` prefixed with `redirect: `.. The `redirect:` prefix for string return values in a controller method signals Spring MVC to perform a client-side redirect, handling the `HttpServletResponse.sendRedirect()` internally.

Q: What is the HTTP response body when a GET request is made to '/greet/Alice'?

A) "Greetings, Alice!". The `@PathVariable` annotation extracts the value from the URL path variable `{name}` and injects it into the method parameter. The method then concatenates this value into the returned String.

Q: An incoming request targets `/echo?status=test`. What value will the `X-Status` header contain in the forwarded request?

A) test. The `addRequestHeader` filter can use variables from path or query parameters. Here, `{status}` refers to the value of the `status` query parameter, which is 'test'.

Q781 medium

Consider a class annotated with `@Configuration`. What is the purpose of the `@Bean` annotation within such a class in the context of IoC?

Q782 medium code output

What is the output of this code snippet, assuming a `Product` with `id=1` and `name="Laptop"` exists in the database?

java

import org.springframework.data.jpa.repository.JpaRepository;
import java.util.Optional;

interface ProductRepository extends JpaRepository<Product, Long> {
    Optional<Product> findByName(String name);
}

// Assuming Product and ProductRepository are properly defined and wired
// and 'productRepository' is an injected instance.
// Simulate DB content: Product(id=1, name='Laptop', price=1200.0)
//                     Product(id=2, name='Monitor', price=300.0)

public class TestService {
    ProductRepository productRepository;

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

    public String getProductInfo(String name) {
        return productRepository.findByName(name)
                                .map(Product::getName)
                                .orElse("Product Not Found");
    }
}
// In a conceptual main method or test:
// System.out.println(new TestService(productRepositoryMock).getProductInfo("Laptop"));

Q783 medium code output

What is the expected output after attempting to save a `Department` with a new `Employee` and subsequently removing that employee from the list when `orphanRemoval` is enabled?

java

import jakarta.persistence.*;
import java.util.*;

@Entity
public class Department {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;
    private String name;
    @OneToMany(mappedBy = "department", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Employee> employees = new ArrayList<>();
    // ... constructors, getters, add/remove methods
}

@Entity
public class Employee {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;
    private String name;
    @ManyToOne @JoinColumn(name = "department_id") private Department department;
    // ... constructors, getters, setters
}

// Assume departmentRepository is injected and available
// Assume transaction context is active
Department dept = new Department("IT");
Employee emp1 = new Employee("Alice");
emp1.setDepartment(dept);
dept.getEmployees().add(emp1);
departmentRepository.save(dept); // Saves dept and emp1

dept.getEmployees().remove(emp1);
departmentRepository.save(dept); // Updates dept
System.out.println("Employee Alice status: " + (departmentRepository.findById(dept.getId()).orElse(new Department()).getEmployees().isEmpty() ? "Removed" : "Present"));

Q784 medium

What is the default behavior of `@PathVariable` regarding its `required` attribute?

Q785 medium code output

What is the HTTP status and JSON body returned by the `addItem` method when a POST request is made to `/items` with the JSON body `{"name": "Book"}` (Content-Type: application/json)?

java

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

class Item {
    private String name;
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

@RestController
@RequestMapping("/items")
class ItemController {
    @PostMapping
    public ResponseEntity<Item> addItem(@RequestBody Item item) {
        item.setName(item.getName() + " Added");
        return new ResponseEntity<>(item, HttpStatus.OK);
    }
}

Q786 medium

If a class is annotated with `@Repository` but no specific persistence framework (like JPA or Spring Data JDBC) is configured in the application, what is the effect of the annotation?

Q787 medium code error

What will be the outcome when trying to access the `/data` endpoint of this Spring Boot application if the intention was to return JSON?

java

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

@Controller
public class DataController {

    @GetMapping("/data")
    public MyObject getData() {
        return new MyObject("Test", 123);
    }

    private static class MyObject {
        public String message; public int value;
        public MyObject(String message, int value) { this.message = message; this.value = value; }
    }
}

Q788 medium

In Spring MVC, how do you typically instruct the browser to perform a client-side redirect to a different URL from a controller method?

Q789 medium code output

What is the HTTP response body when a GET request is made to '/greet/Alice'?

java

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class GreetController {
    @GetMapping("/greet/{name}")
    public String greetUser(@PathVariable String name) {
        return "Greetings, " + name + "!";
    }
}

Q790 medium code output

An incoming request targets `/echo?status=test`. What value will the `X-Status` header contain in the forwarded request?

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("query_header_route", r -> r.path("/echo")
                        .and().query("status")
                        .filters(f -> f.addRequestHeader("X-Status", "{status}"))
                        .uri("http://localhost:8083"))
                .build();
    }
}

Q791 medium code output

What is the HTTP status code and response body for a PUT request to `/api/tasks/5` with the JSON body `{"title": "Updated Task", "completed": true}`?

java

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

// Assume Task class has Long id, String title, boolean completed.

@RestController
@RequestMapping("/api/tasks")
public class TaskController {
    private Map<Long, Task> tasks = new HashMap<>();

    public TaskController() {
        tasks.put(5L, new Task(5L, "Original Task", false));
    }

    @PutMapping("/{id}")
    public ResponseEntity<Task> updateTask(@PathVariable Long id, @RequestBody Task taskUpdate) {
        return Optional.ofNullable(tasks.get(id))
                       .map(existingTask -> {
                           existingTask.setTitle(taskUpdate.getTitle());
                           existingTask.setCompleted(taskUpdate.isCompleted());
                           tasks.put(id, existingTask);
                           return ResponseEntity.ok(existingTask);
                       })
                       .orElse(ResponseEntity.notFound().build());
    }
}

Q792 medium

Once a `ResponseEntity` object has been created (e.g., `ResponseEntity.ok().body(data)`), can its HTTP status code or headers be directly modified?

Q793 medium code output

What is the HTTP response status code and `Location` header value when making a GET request to `/legacy-url`?

java

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

@Controller
public class RedirectController {

    @GetMapping("/legacy-url")
    public String redirectToNewUrl() {
        return "redirect:/new-url";
    }
}

Q794 medium code output

Given the controller and a Thymeleaf template `product.html` containing `<h1 th:text='${productName}'></h1>`, what is the HTTP response body when accessing `/product-details`?

java

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

@Controller
public class ProductController {

    @GetMapping("/product-details")
    public String showProductDetails(Model model) {
        model.addAttribute("productName", "Laptop Pro");
        return "product";
    }
}

Q795 medium code error

What will be the outcome when running this Spring Boot application?

java

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

public interface Theme {
    String getName();
}

@Service("darkTheme")
public class DarkTheme implements Theme {
    @Override public String getName() { return "Dark"; }
}

@Service("lightTheme")
public class LightTheme implements Theme {
    @Override public String getName() { return "Light"; }
}

@Component
public class UserSettings {
    private final Theme activeTheme;

    @Autowired // Ambiguous constructor, @Qualifier missing
    public UserSettings(Theme activeTheme) {
        this.activeTheme = activeTheme;
    }

    public String getCurrentTheme() {
        return activeTheme.getName();
    }
}

Q796 medium

According to REST principles, which HTTP method should be used for retrieving resource representations without causing any side effects on the server, ensuring the operation is both safe and idempotent?

Q797 medium code output

If the `ItemServiceClient` fails to connect to the backend service, and a fallback factory is configured, what will be the output?

java

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.cloud.openfeign.FallbackFactory;
import org.springframework.stereotype.Component;

interface ItemServiceClient {
    @GetMapping("/items")
    String getItems();
}

@FeignClient(name = "itemService", url = "http://localhost:8083", fallbackFactory = ItemServiceFallbackFactory.class)
interface ItemServiceClientFeign extends ItemServiceClient {}

@Component
class ItemServiceFallbackFactory implements FallbackFactory<ItemServiceClient> {
    @Override
    public ItemServiceClient create(Throwable cause) {
        return () -> "Fallback: Could not retrieve items due to: " + cause.getClass().getSimpleName();
    }
}

public class TestApplication {
    public static void main(String[] args) {
        ItemServiceFallbackFactory factory = new ItemServiceFallbackFactory();
        ItemServiceClient client = factory.create(new RuntimeException("Connection Refused"));
        System.out.println(client.getItems());
    }
}

Q798 medium code output

What is the output of this Spring Boot application when run without setting the 'app.feature.enabled' property?

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;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;

@SpringBootApplication
public class MyApp {
    public static void main(String[] args) {
        try {
            ApplicationContext context = SpringApplication.run(MyApp.class, args);
            FeatureService service = context.getBean(FeatureService.class);
            System.out.println(service.getFeatureStatus());
        } catch (NoSuchBeanDefinitionException e) {
            System.out.println("Error: " + e.getBeanType().getName() + " bean not found.");
        } catch (Exception e) {
            System.out.println("An unexpected error occurred: " + e.getMessage());
        }
    }
}

class FeatureService {
    public String getFeatureStatus() { return "Feature is enabled!"; }
}

@Configuration
class AppConfig {
    @Bean
    @ConditionalOnProperty(name = "app.feature.enabled", havingValue = "true", matchIfMissing = false)
    public FeatureService featureService() {
        return new FeatureService();
    }
}

Q799 medium code output

What is the console output when a GET request is made to `/info` in this Spring Boot application with multiple interceptors?

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;
import java.util.Objects;

@Component
class Interceptor1 implements HandlerInterceptor {
    @Override public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object handler) { System.out.println("Int1: pre"); return true; }
    @Override public void postHandle(HttpServletRequest req, HttpServletResponse res, Object handler, ModelAndView mv) { System.out.println("Int1: post"); }
    @Override public void afterCompletion(HttpServletRequest req, HttpServletResponse res, Object handler, Exception ex) { System.out.println("Int1: after"); }
}

@Component
class Interceptor2 implements HandlerInterceptor {
    @Override public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object handler) { System.out.println("Int2: pre"); return true; }
    @Override public void postHandle(HttpServletRequest req, HttpServletResponse res, Object handler, ModelAndView mv) { System.out.println("Int2: post"); }
    @Override public void afterCompletion(HttpServletRequest req, HttpServletResponse res, Object handler, Exception ex) { System.out.println("Int2: after"); }
}

@Configuration
class MvcConfig implements WebMvcConfigurer {
    private final Interceptor1 int1; private final Interceptor2 int2;
    public MvcConfig(Interceptor1 int1, Interceptor2 int2) { this.int1 = int1; this.int2 = int2; }
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(int1).addPathPatterns("/info");
        registry.addInterceptor(int2).addPathPatterns("/info");
    }
}

@RestController
class InfoController {
    @GetMapping("/info")
    public String getInfo() {
        System.out.println("Controller: Showing Info");
        return "Info";
    }
}

Q800 medium code error

A client sends a POST request to `/items` with a JSON body `{"name": "Test Item"}` but sets the `Content-Type` header to `text/plain`. What error will occur with the following controller method?

java

package com.example.demo;
import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;

@RestController
public class ItemController {
    @PostMapping("/items")
    public ResponseEntity<String> createItem(@RequestBody Item item) {
        return ResponseEntity.ok("Item created: " + item.getName());
    }
}
// Item class has a default constructor and setters.

🌱 Spring Boot MCQ Questions – Page 40