@GetMapping for GET requests in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Spring Boot controller method?

Consider this Spring Boot controller method annotated with @GetMapping. What will be the HTTP response body when a GET request is made to /hello?

Spring Boot

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

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello, World!";
    }
}

A A 404 Not Found error because no view is returned

B "Hello, World!" as plain text in the HTTP response body

C A JSON object {"message": "Hello, World!"}

D An empty HTTP response with status 200 OK

💡 Hint

Remember that @RestController combines @Controller and @ResponseBody, so the return value is sent directly as the response body.

The @RestController annotation tells Spring Boot to send the return value of the method directly as the HTTP response body. Since the method returns a String, the response body will contain exactly that string as plain text.

Option B is incorrect because the method returns a String, not a JSON object. Option B is wrong because the method handles the GET request properly. Option B is wrong because the response body is not empty.

📝 Syntax

intermediate

Which @GetMapping annotation syntax correctly maps to the URL path "/users/{id}"?

You want to create a GET endpoint that accepts a user ID as a path variable. Which of the following @GetMapping annotations is correct?

A @GetMapping("/users/{id}")

B @GetMapping("/users/${id}")

C @GetMapping("/users/:id")

D @GetMapping("/users/id")

💡 Hint

Path variables in Spring Boot use curly braces {} in the URL pattern.

In Spring Boot, path variables are defined using curly braces in the URL pattern, like /users/{id}. This tells Spring to capture the value in that part of the URL and pass it to the method.

Options A, C, and D use incorrect syntax for path variables.

🔧 Debug

advanced

Why does this @GetMapping method cause a 405 Method Not Allowed error?

Examine the following controller code. When a GET request is sent to "/data", the server responds with 405 Method Not Allowed. Why?

Spring Boot

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

@RestController
public class DataController {
    @PostMapping("/data")
    public String postData() {
        return "Data posted";
    }

    @GetMapping("/data")
    public String getData() {
        return "Data fetched";
    }
}

A There is a conflict because both @PostMapping and @GetMapping use the same path, causing ambiguity

B The @GetMapping method is missing @ResponseBody, so it does not handle GET requests properly

C The controller class is annotated with @RestController, so both methods should work; the error is elsewhere

D The server is misconfigured and blocks GET requests to /data

💡 Hint

Check if the annotations and method signatures are correct and if the server supports GET requests.

Both methods are correctly annotated and the controller uses @RestController, which combines @Controller and @ResponseBody. Having both @PostMapping and @GetMapping on the same path is allowed and not ambiguous.

A 405 error usually means the HTTP method is not allowed by the server or a filter. The code itself is correct, so the problem is likely outside this snippet, such as server configuration or security settings blocking GET requests.

❓ state_output

advanced

What is the value of the path variable 'id' when this GET request is handled?

Given this controller method, what will be the value of the parameter 'id' when a GET request is made to /items/42?

Spring Boot

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

@RestController
public class ItemController {
    @GetMapping("/items/{id}")
    public String getItem(@PathVariable String id) {
        return "Item ID: " + id;
    }
}

A null because the parameter type is String but the path variable is numeric

B 42 as an Integer

C An error because @PathVariable requires an int parameter for numeric values

D "42" as a String

💡 Hint

Path variables are converted to the parameter type if possible. String works for any value.

The path variable 'id' is captured as a String because the method parameter is String. The value "42" from the URL is passed as the string "42".

Spring Boot can convert path variables to many types, but String works for all values without error.

🧠 Conceptual

expert

Which statement about @GetMapping in Spring Boot is TRUE?

Select the one true statement about the @GetMapping annotation in Spring Boot.

A @GetMapping is a composed annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.GET)

B @GetMapping requires the method to have no parameters

C @GetMapping automatically serializes the return value to JSON regardless of controller type

D @GetMapping can only be used on methods that return a view name, not on REST endpoints

💡 Hint

Think about what @GetMapping replaces or simplifies in Spring MVC.

@GetMapping is a shortcut annotation that is equivalent to using @RequestMapping with method = RequestMethod.GET. It can be used on any method handling GET requests, whether returning views or REST data.

Option A is false because @GetMapping can be used for REST endpoints. Option A is false because serialization depends on @RestController or @ResponseBody, not @GetMapping itself. Option A is false because methods can have parameters, such as path variables or request parameters.