@GetMapping for GET requests in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a GET endpoint using @GetMapping.

Spring Boot

public class HelloController {
    @[1]("/hello")
    public String sayHello() {
        return "Hello, world!";
    }
}

Drag options to blanks, or click blank then click option'

AGetMapping

BDeleteMapping

CRequestMapping

DPostMapping

Attempts:

3 left

💡 Hint

Common Mistakes

Using @PostMapping instead of @GetMapping

Forgetting the annotation entirely

The @GetMapping annotation is used to map HTTP GET requests to the method.

2fill in blank

medium

Complete the code to specify the path for the GET request.

Spring Boot

@GetMapping(path = "[1]")
public String greet() {
    return "Hi!";
}

Drag options to blanks, or click blank then click option'

A/Greet

B/greet

Cgreet

Dgreet/

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the leading slash

Using uppercase letters in path inconsistently

The path should start with a slash / to define the endpoint URL correctly.

3fill in blank

hard

Fix the error in the annotation to correctly map a GET request.

Spring Boot

@[1]("/welcome")
public String welcome() {
    return "Welcome!";
}

Drag options to blanks, or click blank then click option'

AGetMapping

BGetmapping

CPostMapping

DRequestMapping

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase letters in annotation name

Using @PostMapping by mistake

The annotation is case-sensitive and must be exactly @GetMapping.

4fill in blank

hard

Fill both blanks to create a GET endpoint that returns a greeting message.

Spring Boot

public class GreetingController {
    @[1]([2] = "/greet")
    public String greet() {
        return "Hello!";
    }
}

Drag options to blanks, or click blank then click option'

AGetMapping

Bpath

Cvalue

DPostMapping

Attempts:

3 left

💡 Hint

Common Mistakes

Using @PostMapping instead of @GetMapping

Using an incorrect attribute name

@GetMapping is the correct annotation and value is the common attribute to specify the path.

5fill in blank

hard

Fill all three blanks to create a GET endpoint with a path and a method returning a string.

Spring Boot

public class MyController {
    @[1]([2] = "/hello")
    public [3] sayHello() {
        return "Hello!";
    }
}

Drag options to blanks, or click blank then click option'

AGetMapping

Bpath

CString

DPostMapping

Attempts:

3 left

💡 Hint

Common Mistakes

Using @PostMapping instead of @GetMapping

Using 'value' instead of 'path' attribute

Wrong return type

The method is annotated with @GetMapping using the path attribute, and the return type is String.

Practice

1. What is the main purpose of the @GetMapping annotation in a Spring Boot application?

easy

A. To map HTTP POST requests to specific controller methods

B. To map HTTP GET requests to specific controller methods

C. To configure database connections

D. To handle exceptions globally

Solution

1. Step 1: Understand HTTP methods in Spring Boot

   Spring Boot uses annotations to map HTTP methods like GET, POST, etc., to controller methods.

2. Step 2: Identify the role of @GetMapping

   @GetMapping specifically maps HTTP GET requests to the annotated method, so when a user visits a URL with a GET request, this method runs.

3. Final Answer:

   To map HTTP GET requests to specific controller methods -> Option B

4. Quick Check:

   @GetMapping = maps GET requests [OK]

Hint: Remember: @GetMapping is for GET requests only [OK]

Common Mistakes:

• Confusing @GetMapping with @PostMapping
• Thinking @GetMapping handles POST or PUT requests
• Assuming it configures database or exceptions

2. Which of the following is the correct syntax to map a GET request to the URL /hello using @GetMapping in Spring Boot?

easy

A. @GetMapping(path = "/hello") public String greet() { return "Hi"; }

B. @GetMapping(/hello) public String greet() { return "Hi"; }

C. @GetMapping('/hello') public String greet() { return "Hi"; }

D. @GetMapping(path = hello) public String greet() { return "Hi"; }

Solution

1. Step 1: Check the correct use of @GetMapping syntax

   @GetMapping requires the path to be a string, usually passed as path = "/url" or simply "/url".

2. Step 2: Identify correct string usage and syntax

   @GetMapping(path = "/hello") public String greet() { return "Hi"; } uses @GetMapping(path = "/hello") which is correct. @GetMapping(/hello) public String greet() { return "Hi"; } misses quotes around /hello. @GetMapping('/hello') public String greet() { return "Hi"; } uses single quotes, invalid for Java string literal. @GetMapping(path = hello) public String greet() { return "Hi"; } misses quotes around hello.

3. Final Answer:

   @GetMapping(path = "/hello") public String greet() { return "Hi"; } -> Option A

4. Quick Check:

   Correct syntax needs quotes and path attribute [OK]

Hint: Always use quotes around URL paths in @GetMapping [OK]

Common Mistakes:

• Omitting quotes around the path string
• Forgetting the leading slash in URL
• Using path without quotes causing syntax errors

3. Given the following Spring Boot controller method, what will be the output when a GET request is made to /welcome?

@GetMapping("/welcome")
public String welcome() {
    return "Welcome to Spring Boot!";
}

medium

A. An empty response

B. HTTP 404 Not Found error

C. "Welcome to Spring Boot!"

D. HTTP 500 Internal Server Error

Solution

1. Step 1: Understand the method mapping and return value

   The method is mapped to GET requests at "/welcome" and returns a plain string.

2. Step 2: Determine the response content

   Since the method returns a string, Spring Boot will send "Welcome to Spring Boot!" as the response body for the GET request.

3. Final Answer:

   "Welcome to Spring Boot!" -> Option C

4. Quick Check:

   GET /welcome returns method's string [OK]

Hint: Returned string is sent as response body by default [OK]

Common Mistakes:

• Expecting a view name instead of response text
• Confusing 404 error when mapping exists
• Assuming empty or error response without cause

4. Identify the error in the following Spring Boot controller method:

@GetMapping("/user/{id}")
public String getUser(@PathVariable int userId) {
    return "User ID: " + userId;
}

medium

A. The @PathVariable parameter name does not match the path variable name

B. The method should return a ResponseEntity instead of String

C. The @GetMapping path should not contain curly braces

D. The method parameter should be of type String, not int

Solution

1. Step 1: Compare path variable name and method parameter

   The path is defined as /user/{id} but the method parameter is named userId without specifying the variable name in @PathVariable.

2. Step 2: Understand @PathVariable name matching

   By default, the parameter name must match the path variable name or be explicitly specified like @PathVariable("id") int userId.

3. Final Answer:

   The @PathVariable parameter name does not match the path variable name -> Option A

4. Quick Check:

   Path variable names must match or be explicitly linked [OK]

Hint: Match @PathVariable name with URL placeholder or specify explicitly [OK]

Common Mistakes:

• Not matching method parameter name with path variable
• Assuming type mismatch causes error here
• Thinking curly braces are invalid in @GetMapping path

5. You want to create a Spring Boot controller method that handles GET requests to /product/{category}/{id} and returns a string combining both path variables. Which of the following method signatures correctly uses @GetMapping and @PathVariable annotations?

hard

A. @GetMapping("/product/{category}/{id}") public String getProduct(String category, int id) { return category + "-" + id; }

B. @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable String cat, @PathVariable int id) { return cat + "-" + id; }

C. @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable int category, @PathVariable String id) { return category + "-" + id; }

D. @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable("category") String cat, @PathVariable("id") int id) { return cat + "-" + id; }

Solution

1. Step 1: Check @GetMapping path and method parameters

   The path has two variables: {category} and {id}. The method must accept two parameters annotated with @PathVariable matching these names or explicitly linked.

2. Step 2: Analyze each option's parameter annotations and types

   @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable String cat, @PathVariable int id) { return cat + "-" + id; } uses parameter names that do not match path variables (cat != category), so fails without explicit names. @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable("category") String cat, @PathVariable("id") int id) { return cat + "-" + id; } explicitly links parameter names to path variables, which is safest. @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable int category, @PathVariable String id) { return category + "-" + id; } swaps types incorrectly. @GetMapping("/product/{category}/{id}") public String getProduct(String category, int id) { return category + "-" + id; } lacks @PathVariable annotations, so variables won't be bound.

3. Step 3: Choose the best correct and safe option

   @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable("category") String cat, @PathVariable("id") int id) { return cat + "-" + id; } explicitly names variables, avoiding errors if parameter names differ from path variables.

4. Final Answer:

   @GetMapping("/product/{category}/{id}") public String getProduct(@PathVariable("category") String cat, @PathVariable("id") int id) { return cat + "-" + id; } -> Option D

5. Quick Check:

   Explicit @PathVariable names ensure correct binding [OK]

Hint: Use @PathVariable("name") if parameter name differs from path variable [OK]

Common Mistakes:

• Omitting @PathVariable annotation
• Mismatching parameter types with path variables
• Not explicitly naming @PathVariable when names differ