Spring Boot MCQ Questions – Page 9 of 49

Q: Beyond managing beans, `ApplicationContext` also provides generic resource loading capabilities. Which prefix typically indicates a resource that should be loaded from the classpath?

C) `classpath:`. The `classpath:` prefix is used to load resources from the classpath, which is a key capability provided by `ApplicationContext` through its `ResourceLoader` interface.

Q: Consider a `UserRegistrationForm` with a `@NotNull` constraint on `username`. If the following controller method is used to process a form submission where `username` is submitted as empty, what error will occur when the method attempts to use the `username`?

A) java.lang.NullPointerException. Without the `@Valid` annotation on the `UserRegistrationForm` parameter, Spring does not trigger validation. If `username` is null (e.g., from an empty form field), attempting to call `toLowerCase()` on it will result in a `NullPointerException`.

Q: What content type is asserted to be present in the response?

C) application/json. The `content().contentType(MediaType.APPLICATION_JSON)` assertion explicitly checks if the response's Content-Type header is `application/json`. The controller returns the JSON payload it received, making this a valid assertion.

Q: What kind of error will occur during the Spring Boot application startup with the following `RestController`?

C) IllegalStateException (Ambiguous mapping) during startup. Spring cannot have two methods mapped to the exact same path and HTTP method (`GET /users`). This ambiguity will cause an `IllegalStateException` during the application startup process.

Q: If a Spring Boot controller adds an attribute `user` to the `Model` like `model.addAttribute("user", userObject);`, how would you typically access this `user` object within a Thymeleaf template?

D) `th:text="${user.name}"`. In Thymeleaf, you access model attributes using the `th:attribute="${attributeName.property}"` syntax, where `${...}` is the standard expression language for variables.

Q: If a GET request handler method in a Spring Boot `@RestController` needs to ensure its response is always of a specific media type, such as `application/xml`, which attribute of `@GetMapping` would you use?

C) produces. The `produces` attribute in `@GetMapping` specifies the media types that the controller method can produce, influencing content negotiation.

Q: What is the output of this code when a POST request is made to '/data' with an empty body?

A) POST Data Received.. The @RequestMapping with RequestMethod.POST explicitly maps the receiveData() method to handle POST requests on the /data path. An empty request body is acceptable unless specific content handling like @RequestBody is used.

Q: What is the output of this code?

A) Hola. When multiple beans of the same type (here, `GreetingService`) are present, Spring usually throws a `NoUniqueBeanDefinitionException`. However, `@Primary` marks `SpanishGreetingService` as the preferred bean to be injected when there's an ambiguity, so 'Hola' is printed.

Q: What is the expected HTTP response if a DELETE request is made to `/api/files/cleanup` and the `fileService.cleanupOldFiles()` method returns `true`?

A) HTTP 200 OK, with body `{"success": true}`.. The method explicitly returns `ResponseEntity.ok()` with a `Map ` containing `"success": true`. Spring Boot will serialize this map into a JSON response body with an HTTP 200 OK status.

Q: Given `application.properties` contains `api.host=example.com` and `api.path=/users` and the following Java code, what does it print?

A) http://example.com/users. Multiple property placeholders can be used together within a single @Value annotation. Spring resolves all placeholders and concatenates the resulting strings.

Q161 medium

Beyond managing beans, `ApplicationContext` also provides generic resource loading capabilities. Which prefix typically indicates a resource that should be loaded from the classpath?

Q162 medium code error

Consider a `UserRegistrationForm` with a `@NotNull` constraint on `username`. If the following controller method is used to process a form submission where `username` is submitted as empty, what error will occur when the method attempts to use the `username`?

java

import jakarta.validation.constraints.NotNull;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.ModelAttribute;

public class UserRegistrationForm {
    @NotNull(message = "Username cannot be null")
    private String username;
    // Getters and Setters, default constructor...
}

@Controller
public class RegistrationController {
    @PostMapping("/register")
    public String registerUser(@ModelAttribute UserRegistrationForm form) {
        // Assume form.username is null from invalid submission without @Valid
        return "welcome/" + form.getUsername().toLowerCase(); 
    }
}

Q163 medium code output

What content type is asserted to be present in the response?

java

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;

@WebMvcTest(controllers = TestController.class)
class TestControllerTest {
    @Autowired
    private MockMvc mockMvc;

    @Test
    void testPostEndpoint() throws Exception {
        mockMvc.perform(post("/api/data")
               .contentType(MediaType.APPLICATION_JSON)
               .content("{"name":"Test"}"))
               .andExpect(content().contentType(MediaType.APPLICATION_JSON));
    }
}

// Assuming TestController has:
// @RestController
// class TestController {
//    @PostMapping("/api/data")
//    public String processData(@RequestBody String data) { return data; }
// }

Q164 medium code error

What kind of error will occur during the Spring Boot application startup with the following `RestController`?

java

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

@RestController
public class MyController {
    @GetMapping("/users")
    public String getAllUsers() {
        return "All users";
    }

    @GetMapping("/users")
    public String getSingleUser() {
        return "Single user";
    }
}

Q165 medium

If a Spring Boot controller adds an attribute `user` to the `Model` like `model.addAttribute("user", userObject);`, how would you typically access this `user` object within a Thymeleaf template?

Q166 medium

If a GET request handler method in a Spring Boot `@RestController` needs to ensure its response is always of a specific media type, such as `application/xml`, which attribute of `@GetMapping` would you use?

Q167 medium code output

What is the output of this code when a POST request is made to '/data' with an empty body?

java

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

@RestController
public class DataController {
    @RequestMapping(value = "/data", method = RequestMethod.POST)
    public String receiveData() {
        return "POST Data Received.";
    }

    @RequestMapping(value = "/data", method = RequestMethod.GET)
    public String getData() {
        return "GET Data Requested.";
    }
}

Q168 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.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Component;

interface GreetingService { String greet(); }
@Component("englishGreeting") static class EnglishGreetingService implements GreetingService { @Override public String greet() { return "Hello"; } }
@Primary @Component("spanishGreeting") static class SpanishGreetingService implements GreetingService { @Override public String greet() { return "Hola"; } }

@SpringBootApplication
public class MyApplication {
    @Autowired private GreetingService greetingService;
    public static void main(String[] args) {
        MyApplication app = SpringApplication.run(MyApplication.class, args).getBean(MyApplication.class);
        System.out.println(app.greetingService.greet());
    }
}

Q169 medium code output

What is the expected HTTP response if a DELETE request is made to `/api/files/cleanup` and the `fileService.cleanupOldFiles()` method returns `true`?

java

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

@RestController
@RequestMapping("/api/files")
public class FileController {

    private FileService fileService;

    // Constructor injected fileService

    @DeleteMapping("/cleanup")
    public ResponseEntity<Map<String, Boolean>> cleanupFiles() {
        boolean cleaned = fileService.cleanupOldFiles();
        return ResponseEntity.ok(Map.of("success", cleaned));
    }
}

Q170 medium code output

Given `application.properties` contains `api.host=example.com` and `api.path=/users` 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 UrlBuilder {
    @Value("http://${api.host}${api.path}")
    private String fullUrl;

    public String getFullUrl() {
        return fullUrl;
    }
}
// In a Spring Boot application, if this component is scanned:
// UrlBuilder builder = applicationContext.getBean(UrlBuilder.class);
// System.out.println(builder.getFullUrl());

Q171 medium

What is the primary benefit of creating a custom qualifier annotation (e.g., `@FastProcessor`) instead of directly using `@Qualifier("fastProcessor")`?

Q172 medium code output

Given the `User` class (with `id` and `name` properties) below, what is the HTTP response body when a GET request is made to '/api/user'?

java

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

// Assuming User class is defined as: class User { private Long id; private String name; public User(Long id, String name) { this.id = id; this.name = name; } public Long getId() { return id; } public String getName() { return name; } }

@RestController
public class UserController {
    @GetMapping("/api/user")
    public User getUser() {
        return new User(101L, "Jane Doe");
    }
}

Q173 medium

How would you use `@Value` to inject the value of the `user.home` system property?

Q174 medium code error

A form-backing object `OrderForm` has a field of a custom type `Address`. If the HTML form includes `<input type="text" name="shippingAddress">` where `shippingAddress` is intended to bind to `OrderForm.address`, which error is most likely to occur without a custom converter?

java

public class Address {
    private String street;
    private String city;
    // Getters and Setters, constructor...
}

public class OrderForm {
    private Address address;
    // Getters and Setters...
}

@Controller
public class OrderController {
    @PostMapping("/order")
    public String processOrder(@ModelAttribute OrderForm orderForm) {
        // Logic to save order
        return "orderConfirmation";
    }
}

Q175 medium code output

What is the HTTP response body when a GET request is made to `/reports/daily`?

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 ReportController {
    @GetMapping("/reports/{reportName:[a-z]+}")
    public String getReport(@PathVariable("reportName") String name) {
        return "Fetching report: " + name.toUpperCase();
    }
}

Q176 medium code error

What error will the ApplicationContext report during initialization given the following classes?

java

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

@Component
class ServiceA {
    @Autowired
    public ServiceA(ServiceB b) {}
}

@Component
class ServiceB {
    @Autowired
    public ServiceB(ServiceA a) {}
}

public class CircularApp {
    public static void main(String[] args) {
        new AnnotationConfigApplicationContext(CircularApp.class.getPackage().getName());
    }
}

Q177 medium code output

What is the HTTP response body when accessing `/users/101` with the following controller?

java

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

@Controller
public class UserController {

    @GetMapping("/users/{userId}")
    @ResponseBody
    public String getUserById(@PathVariable long userId) {
        return "User ID: " + userId;
    }
}

Q178 medium code output

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

java

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Optional;

@RestController
public class MyController {
    @GetMapping("/optional")
    public ResponseEntity<String> getOptionalData() {
        Optional<String> data = Optional.empty(); // Represents no data found
        return data.map(ResponseEntity::ok)
                   .orElseGet(() -> ResponseEntity.notFound().build());
    }
}

Q179 medium

When Spring performs autowiring for a field, which of the following is true?

Q180 medium code error

What error will prevent this code from compiling?

java

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

class MyConstants {
    public static String JSON_TYPE = "application/json";
}

@RestController
public class MyController {

    @GetMapping(value = "/data", produces = MyConstants.JSON_TYPE)
    public String getData() {
        return "{ \"key\": \"value\" }";
    }
}

🌱 Spring Boot MCQ Questions – Page 9