Spring Boot MCQ Questions – Page 8 of 49

Q: What is the output of this code when `App` is executed?

A) 1. Ctor 2. @PostConstruct 3. afterPropertiesSet 4. customInitMethod. The order of initialization callbacks is: constructor -> `@PostConstruct` -> `InitializingBean.afterPropertiesSet()` -> custom `init-method`.

Q: What is the output of this code?

A) NoUniqueBeanDefinitionException: No qualifying bean of type 'MyInterface' available: expected single matching bean but found 2: implA,implB. When multiple beans of the same type (implementing `MyInterface`) are found without a specific qualifier, the `ApplicationContext` throws a `NoUniqueBeanDefinitionException`.

Q: What error will occur when the `/api/data` endpoint is accessed, attempting to return an instance of `MyResponse`?

B) InvalidDefinitionException or JsonMappingException due to serialization failure. Jackson (the default JSON marshaller in Spring Boot) requires public getters for properties to be serialized. Without a `public String getMessage()` method, Jackson cannot discover the 'message' property, leading to an `InvalidDefinitionException` or `JsonMappingException` during serialization.

Q: What error will occur when accessing `/api/product?id=abc` with the following Spring Boot controller?

B) Status 400 (Bad Request) - MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'int'. The `@RequestParam` `id` is expected to be an integer. Passing 'abc' which cannot be converted to an integer will cause a `MethodArgumentTypeMismatchException` and a 400 Bad Request status.

Q: What is the HTTP response body when a GET request is made to `/files/image_01.jpg`?

A) 404 Not Found. The path variable regex `[a-zA-Z0-9]+.txt` specifically requires the file extension to be '.txt'. Since the request uses '.jpg', the path does not match the mapping, resulting in a 404 Not Found error.

Q: What is the expected error when starting this Spring Boot application due to the configuration of `ServiceA` and `ServiceB`?

A) org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'serviceA': Requested bean is currently in creation. This code represents a circular dependency using constructor injection. Spring detects this at startup and throws a `BeanCurrentlyInCreationException` because `ServiceA` needs `ServiceB` and `ServiceB` simultaneously needs `ServiceA` before either can be fully created.

Q: A user named "user" with role "USER" logs into the application and attempts to access the `/admin/task` endpoint. What is the typical HTTP status code and response body content they will receive?

B) HTTP 403 Forbidden, an empty body or a default error page.. The `@PreAuthorize("hasRole('ADMIN')")` annotation denies access before the method execution if the authenticated user (with role 'USER') lacks the 'ADMIN' role, resulting in an HTTP 403 Forbidden status.

Q: What HTTP status code is expected when attempting to access a non-existent endpoint with MockMvc?

C) 404 Not Found. When MockMvc attempts to dispatch a request to a path that does not have a corresponding controller mapping, it correctly returns an HTTP 404 Not Found status. The `status().isNotFound()` assertion verifies this.

Q: What is the output when '/process/data' is accessed, and no `DataAccessException` handler is defined?

A) General Error Handler: Database connection lost. Since `DataAccessException` extends `RuntimeException` (it's a subclass of `NestedRuntimeException` which extends `RuntimeException`), the `@ExceptionHandler(RuntimeException.class)` will catch it. Spring will select the most specific handler, but in this case, `RuntimeException` is the only applicable handler for `DataAccessException`.

Q: To enable automatic validation of a form object passed into a Spring MVC controller method using standard JSR-303/380 annotations (like `@NotNull`, `@Size`), which annotation must be placed directly before the object parameter in the method signature?

A) @Valid. The `@Valid` annotation triggers the validation process for the annotated object based on its JSR-303/380 constraints. It's often used in conjunction with `BindingResult`.

Q141 medium code output

What is the output of this code when `App` is executed?

java

import javax.annotation.PostConstruct;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.context.annotation.*;

class MyInitBean implements InitializingBean {
    public MyInitBean() { System.out.println("1. Ctor"); }
    @PostConstruct public void postConstruct() { System.out.println("2. @PostConstruct"); }
    @Override
    public void afterPropertiesSet() { System.out.println("3. afterPropertiesSet"); }
    public void customInit() { System.out.println("4. customInitMethod"); }
}
@Configuration
public class App {
    @Bean(initMethod = "customInit") public MyInitBean myInitBean() { return new MyInitBean(); }
    public static void main(String[] args) { AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class); context.close(); }
}

Q142 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.stereotype.Component;

interface MyInterface { String getID(); }
@Component("implA") class MyImplA implements MyInterface { public String getID() { return "A"; } }
@Component("implB") class MyImplB implements MyInterface { public String getID() { return "B"; } }

@SpringBootApplication
public class App5 {
    public static void main(String[] args) {
        ApplicationContext ctx = SpringApplication.run(App5.class, args);
        try {
            ctx.getBean(MyInterface.class);
        } catch (Exception e) {
            System.out.println(e.getClass().getSimpleName() + ": " + e.getMessage().split("\n")[0]);
        }
    }
}

Q143 medium code error

What error will occur when the `/api/data` endpoint is accessed, attempting to return an instance of `MyResponse`?

java

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

@RestController
public class MyController {
    @GetMapping("/api/data")
    public MyResponse getData() {
        return new MyResponse("Hello");
    }

    static class MyResponse { // Missing public getter for 'message'
        private String message;
        public MyResponse(String message) { this.message = message; }
    }
}

Q144 medium code error

What error will occur when accessing `/api/product?id=abc` with the following Spring Boot controller?

java

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

@RestController
@RequestMapping("/api")
public class ProductController {

    @GetMapping("/product")
    public String getProduct(@RequestParam int id) {
        return "Product ID: " + id;
    }
}

Q145 medium code output

What is the HTTP response body when a GET request is made to `/files/image_01.jpg`?

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 FileController {
    @GetMapping("/files/{fileName:[a-zA-Z0-9]+}.txt")
    public String getFileContent(@PathVariable String fileName) {
        return "Content of " + fileName + ".txt";
    }
}

Q146 medium code error

What is the expected error when starting this Spring Boot application due to the configuration of `ServiceA` and `ServiceB`?

java

import org.springframework.stereotype.Service;

@Service
public class ServiceA {
    private final ServiceB serviceB;

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

    public String getInfo() { return "From A"; }
}

@Service
public class ServiceB {
    private final ServiceA serviceA;

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

    public String getInfo() { return "From B"; }
}

Q147 medium code output

A user named "user" with role "USER" logs into the application and attempts to access the `/admin/task` endpoint. What is the typical HTTP status code and response body content they will receive?

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.access.prepost.PreAuthorize;
import org.springframework.security.config.annotation.method.configuration.EnableMethodSecurity;
import org.springframework.security.core.userdetails.User;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.provisioning.InMemoryUserDetailsManager;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@Configuration
@EnableMethodSecurity
public class SecurityConfig {
    @Bean
    public UserDetailsService userDetailsService() {
        UserDetails user = User.withUsername("user").password("{noop}password").roles("USER").build();
        return new InMemoryUserDetailsManager(user);
    }
}

@Service
public class AdminService { public String performAdminTask() { return "Admin task performed."; } }

@RestController
public class AdminController {
    private final AdminService adminService;
    public AdminController(AdminService adminService) { this.adminService = adminService; }
    @GetMapping("/admin/task")
    @PreAuthorize("hasRole('ADMIN')")
    public String getAdminTask() { return adminService.performAdminTask(); }
}

Q148 medium code output

What HTTP status code is expected when attempting to access a non-existent endpoint with MockMvc?

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.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

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

    @Test
    void testNonExistentEndpoint() throws Exception {
        mockMvc.perform(get("/api/nonexistent"))
               .andExpect(status().isNotFound());
    }
}

// Assuming TestController has:
// @RestController
// class TestController {
//    // No mapping for /api/nonexistent
//    @GetMapping("/api/hello")
//    public String hello() { return "Hello MockMvc!"; }
// }

Q149 medium code output

What is the output when '/process/data' is accessed, and no `DataAccessException` handler is defined?

java

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

@RestController
public class ProcessingController {

    @GetMapping("/process/data")
    public String processData() {
        throw new DataAccessException("Database connection lost") {};
    }

    @ExceptionHandler(RuntimeException.class)
    public String handleRuntimeException(RuntimeException ex) {
        return "General Error Handler: " + ex.getMessage();
    }
}

Q150 medium

To enable automatic validation of a form object passed into a Spring MVC controller method using standard JSR-303/380 annotations (like `@NotNull`, `@Size`), which annotation must be placed directly before the object parameter in the method signature?

Q151 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("isAuthenticated() and hasRole('EMPLOYEE')")
    public String getEmployeeBenefits() { return "Employee Benefits"; }
}

public class TestRunner {
    public static void main(String[] args) {
        SecurityContextHolder.getContext().setAuthentication(
            new UsernamePasswordAuthenticationToken("manager", "pass", Collections.singletonList(new SimpleGrantedAuthority("ROLE_MANAGER")))
        );
        SecureService service = new SecureService();
        try { System.out.println(service.getEmployeeBenefits()); }
        catch (Exception e) { System.out.println(e.getClass().getSimpleName()); }
    }
}

Q152 medium

Which annotation is a composed annotation that specifically maps HTTP GET requests to a handler method in a `@Controller`?

Q153 medium code error

What is the error in this Spring Boot application configuration regarding the bean's lifecycle method?

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import jakarta.annotation.PostConstruct;

@Configuration
public class AppConfig {

    @Bean
    public MyService myService() {
        return new MyService();
    }
}

class MyService {
    @PostConstruct
    public static void init() { // @PostConstruct methods cannot be static
        System.out.println("MyService initialized.");
    }
}

Q154 medium

When using Spring Security with Thymeleaf forms, what is the typical mechanism used to automatically include a CSRF token in a form to protect against Cross-Site Request Forgery attacks?

Q155 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.Arrays;

public class SecureService {
    @PreAuthorize("hasAnyRole('ADMIN', 'MANAGER')")
    public String getManagementReport() { return "Management Report"; }
}

public class TestRunner {
    public static void main(String[] args) {
        SecurityContextHolder.getContext().setAuthentication(
            new UsernamePasswordAuthenticationToken("john", "pass", Arrays.asList(new SimpleGrantedAuthority("ROLE_MANAGER")))
        );
        SecureService service = new SecureService();
        try { System.out.println(service.getManagementReport()); }
        catch (Exception e) { System.out.println(e.getClass().getSimpleName()); }
    }
}

Q156 medium code output

What is the output of this code when a GET request is made to '/config'?

java

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.HashMap;
import java.util.Map;

@RestController
public class ConfigController {
    @RequestMapping("/config")
    public Map<String, Object> getConfig() {
        Map<String, Object> config = new HashMap<>();
        config.put("version", "1.0");
        config.put("active", true);
        return config;
    }
}

Q157 medium code output

What is the value printed by the `System.out.println` statement?

java

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

@Component class CounterComponent {
    private int count = 0;
    public void increment() { count++; }
    public int getCount() { return count; }
}

@SpringBootApplication
public class DemoApplication {
    public static void main(String[] args) {
        var context = SpringApplication.run(DemoApplication.class, args);
        var c1 = context.getBean(CounterComponent.class);
        c1.increment();
        var c2 = context.getBean(CounterComponent.class);
        c2.increment();
        System.out.println(c1.getCount());
    }
}

Q158 medium

What is the primary purpose of the `@Bean` annotation in a Spring `@Configuration` class?

Q159 medium code output

What does this code print to the console?

java

package com.example;

import jakarta.persistence.*;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.transaction.annotation.Transactional;

@Entity
public class Product {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private double price;

    public Product() {}
    public Product(Long id, String name, double price) { this.id = id; this.name = name; this.price = price; }
    public String getName() { return name; }
    public double getPrice() { return price; }
}

interface ProductRepository extends JpaRepository<Product, Long> {
    @Modifying
    @Transactional
    @Query("UPDATE Product p SET p.price = :newPrice WHERE p.id = :id")
    int updateProductPriceJPQL(@Param("newPrice") double newPrice, @Param("id") Long id);
}

// Assume ProductRepository is autowired as 'productRepository'
// And the database contains: Product(id=1, name='Headphones', price=100.00)
int updatedCount = productRepository.updateProductPriceJPQL(120.00, 1L);
System.out.println(updatedCount);

Q160 medium code output

What is the output of this code when the `main` method of `MyApplication` is executed?

java

// src/main/java/com/example/app/MyApplication.java
package com.example.app;

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

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

// src/main/java/com/example/other/MyComponent.java
package com.example.other;

import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;

@Component
class MyComponent {
    @PostConstruct
    public void init() {
        System.out.println("MyComponent Initialized");
    }
}

🌱 Spring Boot MCQ Questions – Page 8