Spring Boot MCQ Questions – Page 6 of 49

Q: What is the HTTP status code and response body for a PUT request to `/api/widgets/1` with the JSON body `{"name": "Mega Widget"}`?

A) Status: 200 OK, Body: {"id":1,"name":"Mega Widget","category":"Electronics"}. The `@PutMapping` method updates only the `name` field if it's provided in the request body. Since 'category' is not provided in the request, its value from the existing object ('Electronics') is retained. The method explicitly returns a 200 OK status with the updated `existingWidget`.

Q: Which attribute of `@RequestParam` is used to provide a fallback value for the parameter if it is not present in the HTTP request?

C) `defaultValue`. The `defaultValue` attribute allows you to specify a literal string value that will be used for the parameter if it is not found in the request.

Q: To handle a GET request where a path segment (e.g., an 'id') is optional (e.g., `/items` versus `/items/{id}`), what is the most common and robust approach in Spring Boot?

B) Defining separate `@GetMapping` annotations for each path variation.. The most common and readable way to handle truly optional path segments is to define distinct `@GetMapping` methods, each with a different path pattern, covering all expected variations.

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

A) 1. Ctor 2. setBeanName: myNamedBean 3. Retrieved: myNamedBean. The `setBeanName` method of the `BeanNameAware` interface is called after instantiation but before initialization, allowing the bean to know its name in the container.

Q: What is the consequence of adding `@ComponentScan(basePackages = "com.example.other")` to the `@SpringBootApplication` class in `com.example.app` while expecting components in `com.example.app.service` to be scanned?

C) A `NoSuchBeanDefinitionException` for `MyService` will occur if it's injected elsewhere.. `@SpringBootApplication` already includes `@ComponentScan` by default, scanning its own package and sub-packages. Explicitly adding `@ComponentScan(basePackages = "com.example.other")` overrides this default behavior. As a result, `MyService` in `com.example.app.service` will no longer be scanned, leading to a `NoSuchBeanDefinitionException` if it's referenced.

Q: When Spring encounters multiple beans of the same type during autowiring, and there's no primary bean or qualifier specified, what exception is typically thrown?

C) NoUniqueBeanDefinitionException. NoUniqueBeanDefinitionException is thrown when Spring finds more than one bean of the requested type and cannot determine which one to inject without further instructions (like @Primary or @Qualifier).

Q: Assume there is a `@RestController` with a `/hello` endpoint that returns "Hello from Controller!". What does this code print to the console when `testHelloEndpoint` is executed?

A) Hello from Controller!. `@SpringBootTest(webEnvironment = WebEnvironment.MOCK)` loads the full context without starting a real HTTP server. `@AutoConfigureMockMvc` provides a `MockMvc` instance to simulate HTTP requests internally, capturing the controller's response.

Q: Which of the following `@RequestMapping` attributes specifies the media types that the controller method can consume (i.e., accept from the request body)?

B) consumes. The `consumes` attribute is used to specify the media types that the endpoint can process from the request body, typically checked against the `Content-Type` header of the incoming request.

Q: Which Spring Boot annotation is primarily used to map HTTP DELETE requests to a specific handler method in a REST controller?

B) @DeleteMapping. @DeleteMapping is a composed annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.DELETE). It is specifically designed for mapping HTTP DELETE requests.

Q: An unauthenticated client attempts to access the `/css/style.css` endpoint. What is the expected HTTP status code and response body?

B) HTTP 200 OK, "/* CSS content */". The `requestMatchers("/css/**").permitAll()` configuration explicitly allows unauthenticated access to the `/css/style.css` path, so the client receives the resource with an HTTP 200 OK status.

Q101 medium code output

What is the HTTP status code and response body for a PUT request to `/api/widgets/1` with the JSON body `{"name": "Mega Widget"}`?

java

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

// Assume Widget class has Long id, String name, String category (nullable).

@RestController
@RequestMapping("/api/widgets")
public class WidgetController {
    private Map<Long, Widget> widgets = new HashMap<>();

    public WidgetController() {
        widgets.put(1L, new Widget(1L, "Old Widget", "Electronics"));
    }

    @PutMapping("/{id}")
    public ResponseEntity<Widget> updateWidget(@PathVariable Long id, @RequestBody Widget widgetDetails) {
        if (!widgets.containsKey(id)) {
            return ResponseEntity.status(404).build();
        }
        Widget existingWidget = widgets.get(id);
        // Only update provided fields. PUT is generally full replacement, but this code shows partial update logic.
        if (widgetDetails.getName() != null) {
            existingWidget.setName(widgetDetails.getName());
        }
        // Category is not in request body, so it remains unchanged by this logic.
        widgets.put(id, existingWidget);
        return ResponseEntity.status(200).body(existingWidget);
    }
}

Q102 medium

Which attribute of `@RequestParam` is used to provide a fallback value for the parameter if it is not present in the HTTP request?

Q103 medium

To handle a GET request where a path segment (e.g., an 'id') is optional (e.g., `/items` versus `/items/{id}`), what is the most common and robust approach in Spring Boot?

Q104 medium code output

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

java

import org.springframework.beans.factory.BeanNameAware;
import org.springframework.context.annotation.*;
import org.springframework.stereotype.Component;

@Component
class MyNamedBean implements BeanNameAware {
    private String name;
    public MyNamedBean() { System.out.println("1. Ctor"); }
    @Override
    public void setBeanName(String name) { this.name = name; System.out.println("2. setBeanName: " + name); }
    public String getBeanName() { return name; }
}
@ComponentScan
public class App {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(App.class);
        MyNamedBean bean = context.getBean(MyNamedBean.class);
        System.out.println("3. Retrieved: " + bean.getBeanName());
        context.close();
    }
}

Q105 medium code error

What is the consequence of adding `@ComponentScan(basePackages = "com.example.other")` to the `@SpringBootApplication` class in `com.example.app` while expecting components in `com.example.app.service` to be scanned?

java

package com.example.app;

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.SpringApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.stereotype.Service;

package com.example.app.service;

@Service
public class MyService {
    // Service implementation
}

// In com.example.app package
@SpringBootApplication
@ComponentScan(basePackages = "com.example.other")
public class ScanApp {
    public static void main(String[] args) {
        SpringApplication.run(ScanApp.class, args);
    }
}

Q106 medium

When Spring encounters multiple beans of the same type during autowiring, and there's no primary bean or qualifier specified, what exception is typically thrown?

Q107 medium code output

Assume there is a `@RestController` with a `/hello` endpoint that returns "Hello from Controller!". What does this code print to the console when `testHelloEndpoint` is executed?

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.test.web.servlet.MockMvc;
import org.junit.jupiter.api.Test;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@SpringBootTest(webEnvironment = WebEnvironment.MOCK)
@AutoConfigureMockMvc
public class MockMvcTest {

    @Autowired
    private MockMvc mockMvc;

    @Test
    void testHelloEndpoint() throws Exception {
        String response = mockMvc.perform(get("/hello"))
                                 .andExpect(status().isOk())
                                 .andReturn().getResponse().getContentAsString();
        System.out.println(response);
    }
}

Q108 medium

Which of the following `@RequestMapping` attributes specifies the media types that the controller method can consume (i.e., accept from the request body)?

Q109 medium

Which Spring Boot annotation is primarily used to map HTTP DELETE requests to a specific handler method in a REST controller?

Q110 medium code output

An unauthenticated client attempts to access the `/css/style.css` endpoint. What is the expected HTTP status code and response body?

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.web.SecurityFilterChain;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import static org.springframework.security.config.Customizer.withDefaults;

@Configuration
@EnableWebSecurity
public class SecurityConfig {
    @Bean
    public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
        http.authorizeHttpRequests(authorize -> authorize
                .requestMatchers("/css/**", "/js/**", "/images/**").permitAll()
                .anyRequest().authenticated()
            )
            .formLogin(withDefaults())
            .csrf(csrf -> csrf.disable());
        return http.build();
    }
}

@RestController
public class ResourceController {
    @GetMapping("/css/style.css")
    public String getCss() { return "/* CSS content */"; }

    @GetMapping("/app/data")
    public String getAppData() { return "Application data"; }
}

Q111 medium code error

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

java

import org.springframework.web.bind.annotation.*;
import java.util.Optional;

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

    @GetMapping("/data")
    public String getData(@RequestParam Optional<Integer> id) {
        return "ID: " + id.orElse(0);
    }
}

Q112 medium

When implementing a service method that orchestrates multiple repository operations, what is a common best practice regarding data consistency and failure handling?

Q113 medium code output

Assuming H2 database is on the classpath, what is the output of this code when the `main` method of `MyApplication` is executed?

java

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

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.context.ApplicationContext;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.annotation.Bean;

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

    @Bean
    public CommandLineRunner checkDataSourceBean(ApplicationContext context) {
        return args -> {
            try {
                context.getBean(javax.sql.DataSource.class);
                System.out.println("DataSource bean found");
            } catch (NoSuchBeanDefinitionException e) {
                System.out.println("DataSource bean not found");
            }
        };
    }
}

Q114 medium code error

What happens if a client attempts to access `/items/{id}` with `{id}` being a non-numeric string (e.g., `/items/abc`) using this 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 ItemController {

    @GetMapping("/items/{id}")
    @ResponseBody
    public String getItem(@PathVariable("id") Long itemId) {
        return "Item ID: " + itemId;
    }
}

Q115 medium code output

Assuming a Spring Boot application with the following controller, what is the outcome regarding the view and model attributes if a request is made to `/data`?

java

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

@Controller
public class DataController {

    @GetMapping("/data")
    public ModelAndView getData() {
        ModelAndView mav = new ModelAndView("showData");
        mav.addObject("item", "Laptop");
        mav.addObject("price", 1200.00);
        return mav;
    }
}

Q116 medium code error

What will happen when this application attempts to start if `spring.main.web-application-type=NONE` is configured in `application.properties`?

java

package com.example.app;

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

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

    // ... endpoint definitions
}

Q117 medium code error

What error will occur when Spring attempts to autowire `MyProcessor` into `ServiceUser`?

java

import org.springframework.stereotype.Component;

interface MyProcessor {
    void process();
}

@Component
class DefaultProcessor implements MyProcessor {
    @Override public void process() {}
}

@Component
class SpecialProcessor implements MyProcessor {
    @Override public void process() {}
}

@Component
class ServiceUser {
    private final MyProcessor processor;
    public ServiceUser(MyProcessor processor) {
        this.processor = processor;
    }
}

Q118 medium

To enable Cross-Origin Resource Sharing (CORS) for a specific controller method, allowing requests from `http://example.com`, which annotation would be applied to the method?

Q119 medium code error

Given the following Spring Boot configuration with `proxyBeanMethods = false`, what will be the runtime error when `MyService` attempts to use `dependencyService`?

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.beans.factory.annotation.Autowired;

public class DependencyService {
    public String getData() { return "Data"; }
}

public class MyService {
    @Autowired
    private DependencyService dependencyService;
    public String getInfo() {
        if (dependencyService == null) throw new IllegalStateException("DependencyService not injected!");
        return "MyService info: " + dependencyService.getData();
    }
}

@Configuration(proxyBeanMethods = false)
public class AppConfig {
    @Bean
    public DependencyService dependencyService() { return new DependencyService(); }

    @Bean
    public MyService myService() {
        // Direct call, bypassing Spring's full bean lifecycle management
        return new MyService(); 
    }

    // Assume the main application calls: 
    // context.getBean(MyService.class).getInfo();
}

Q120 medium code error

What is the error encountered when a client sends a POST request to `/items` with an empty request body, given the following Spring Boot 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 6