Request mapping by method and path in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the HTTP response status when accessing the mapped endpoint?

Consider this Spring Boot controller method:

@RestController
public class MyController {
    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String greet() {
        return "Hello World";
    }
}

What will be the HTTP status code when a client sends a GET request to /hello?

Spring Boot

@RestController
public class MyController {
    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String greet() {
        return "Hello World";
    }
}

A 200 OK

B 404 Not Found

C 500 Internal Server Error

D 405 Method Not Allowed

💡 Hint

The method matches the GET request for the path exactly.

The method is mapped to GET requests at path '/hello'. When a GET request is sent to '/hello', the method returns a string and Spring Boot responds with status 200 OK by default.

📝 Syntax

intermediate

Which option correctly maps POST requests to /submit?

You want to create a Spring Boot controller method that handles POST requests to the path /submit. Which of the following method annotations is correct?

A @RequestMapping(path = "/submit", method = RequestMethod.GET)

B @RequestMapping(value = "/submit", method = RequestMethod.POST)

C @RequestMapping(value = "/submit")

D @RequestMapping(method = RequestMethod.POST)

💡 Hint

You need to specify both the path and the POST method explicitly.

Option B correctly specifies the path '/submit' and the HTTP method POST. Option B uses GET instead of POST. Option B does not specify the method, so it defaults to all methods. Option B specifies POST but no path, so it won't map to '/submit'.

🔧 Debug

advanced

Why does this controller method cause a 405 error on POST /data?

Given this controller:

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

When a client sends a POST request to /data, the server responds with 405 Method Not Allowed. Why?

Spring Boot

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

A Because the controller is missing @PostMapping annotation

B Because the method throws an exception on POST requests

C Because the path /data is invalid

D Because there is no method mapped to POST requests at /data

💡 Hint

Check which HTTP methods are allowed for the path.

The controller only maps GET requests to /data. POST requests to /data have no matching handler, so Spring Boot returns 405 Method Not Allowed.

🧠 Conceptual

advanced

What happens if two methods map to the same path but different HTTP methods?

In a Spring Boot controller, you have:

@RequestMapping(value = "/item", method = RequestMethod.GET)
public String getItem() { return "Get"; }

@RequestMapping(value = "/item", method = RequestMethod.POST)
public String postItem() { return "Post"; }

What happens when a client sends a GET request and a POST request to /item?

Spring Boot

@RequestMapping(value = "/item", method = RequestMethod.GET)
public String getItem() { return "Get"; }

@RequestMapping(value = "/item", method = RequestMethod.POST)
public String postItem() { return "Post"; }

A GET requests return "Get" and POST requests return "Post"

B Both GET and POST requests return "Get"

C Both GET and POST requests return "Post"

D Requests cause a conflict error at startup

💡 Hint

Spring Boot matches methods by both path and HTTP method.

Spring Boot allows multiple methods mapped to the same path if they differ by HTTP method. GET requests call getItem(), POST requests call postItem().

❓ state_output

expert

What is the response body when sending a PUT request to /update with this controller?

Given this Spring Boot controller:

@RestController
public class UpdateController {
    @RequestMapping(value = "/update", method = {RequestMethod.POST, RequestMethod.PUT})
    public String update() {
        return "Updated";
    }
}

What will be the response body when a client sends a PUT request to /update?

Spring Boot

@RestController
public class UpdateController {
    @RequestMapping(value = "/update", method = {RequestMethod.POST, RequestMethod.PUT})
    public String update() {
        return "Updated";
    }
}

A "Method Not Allowed"

B "Not Found"

C "Updated"

D Empty response body

💡 Hint

The method handles both POST and PUT requests.

The method is mapped to both POST and PUT requests at /update. A PUT request will invoke this method and return "Updated" as the response body.

Practice

1. What does the @RequestMapping annotation do in Spring Boot?

easy

A. It styles the HTML page returned by the controller.

B. It creates a new database connection automatically.

C. It links a URL path and HTTP method to a specific method in a controller.

D. It schedules background tasks to run periodically.

Solution

1. Step 1: Understand the purpose of @RequestMapping

   @RequestMapping is used to connect web requests to controller methods in Spring Boot.

2. Step 2: Identify what it links

   It links both the URL path and the HTTP method (GET, POST, etc.) to the method that should handle the request.

3. Final Answer:

   It links a URL path and HTTP method to a specific method in a controller. -> Option C

4. Quick Check:

   @RequestMapping links URL and method [OK]

Hint: Remember: @RequestMapping connects URL + HTTP method to code [OK]

Common Mistakes:

• Thinking @RequestMapping styles HTML output
• Confusing it with database or scheduling annotations
• Assuming it only maps URL without HTTP method

2. Which of the following is the correct way to map a GET request to path "/home" using @RequestMapping?

easy

A. @RequestMapping(route = "/home", method = GET)

B. @RequestMapping(path = "/home", method = RequestMethod.GET)

C. @RequestMapping(value = "/home", type = "GET")

D. @RequestMapping(method = "GET", url = "/home")

Solution

1. Step 1: Recall correct @RequestMapping syntax

   The correct syntax uses 'path' or 'value' for URL and 'method' with RequestMethod enum for HTTP method.

2. Step 2: Match options with syntax

   @RequestMapping(path = "/home", method = RequestMethod.GET) uses path and method=RequestMethod.GET correctly. Others use invalid attribute names or wrong types.

3. Final Answer:

   @RequestMapping(path = "/home", method = RequestMethod.GET) -> Option B

4. Quick Check:

   Correct syntax [OK]

Hint: Use 'path' and RequestMethod.GET for GET mapping [OK]

Common Mistakes:

• Using 'url' instead of 'path' or 'value'
• Passing HTTP method as string instead of RequestMethod enum
• Using wrong attribute names like 'route' or 'type'

3. Given this controller method:

@RequestMapping(path = "/test", method = RequestMethod.POST)
public String test() {
    return "Success";
}

What happens when a client sends a GET request to "/test"?

medium

A. The server crashes with an exception.

B. The method runs and returns "Success".

C. Spring returns a 404 Not Found error.

D. Spring returns a 405 Method Not Allowed error.

Solution

1. Step 1: Identify the mapped HTTP method

   The method is mapped only to POST requests at path "/test".

2. Step 2: Understand what happens on GET request

   A GET request to the same path is not handled, so Spring returns 405 Method Not Allowed.

3. Final Answer:

   Spring returns a 405 Method Not Allowed error. -> Option D

4. Quick Check:

   GET to POST-only path = 405 error [OK]

Hint: GET request to POST-only path causes 405 error [OK]

Common Mistakes:

• Assuming GET runs the POST method
• Thinking it returns 404 Not Found instead
• Believing server crashes on wrong method

4. What is wrong with this mapping?

@RequestMapping(path = "/data", method = "POST")
public String saveData() {
    return "Saved";
}

medium

A. The method attribute should use RequestMethod.POST, not a string.

B. The path attribute cannot be used with @RequestMapping.

C. The method must return void, not String.

D. The method name must be saveDataPost, not saveData.

Solution

1. Step 1: Check method attribute type

   The method attribute expects a RequestMethod enum value, not a string.

2. Step 2: Identify correct usage

   Using method = "POST" is invalid; it should be method = RequestMethod.POST.

3. Final Answer:

   The method attribute should use RequestMethod.POST, not a string. -> Option A

4. Quick Check:

   method attribute needs RequestMethod enum [OK]

Hint: Use RequestMethod.POST enum, not string "POST" [OK]

Common Mistakes:

• Passing HTTP method as string instead of enum
• Thinking path attribute is invalid
• Assuming return type or method name causes error

5. You want to create two methods in a controller: one handles GET requests at "/items" and another handles POST requests at the same path "/items". Which is the best way to do this?

hard

A. Use two methods with @RequestMapping(path = "/items", method = RequestMethod.GET) and @RequestMapping(path = "/items", method = RequestMethod.POST).

B. Use one method with @RequestMapping(path = "/items") and check HTTP method inside the method manually.

C. Use @RequestMapping(path = "/items") on both methods without specifying method attribute.

D. Use @RequestMapping(method = RequestMethod.GET) on one method and @RequestMapping(method = RequestMethod.POST) on the other without path.

Solution

1. Step 1: Understand how to map same path with different methods

   Spring allows multiple methods mapped to the same path but different HTTP methods using method attribute.

2. Step 2: Evaluate options

   Use two methods with @RequestMapping(path = "/items", method = RequestMethod.GET) and @RequestMapping(path = "/items", method = RequestMethod.POST). correctly uses two methods with same path but different HTTP methods. Use one method with @RequestMapping(path = "/items") and check HTTP method inside the method manually. is less clean and error-prone. Use @RequestMapping(path = "/items") on both methods without specifying method attribute. causes ambiguity. Use @RequestMapping(method = RequestMethod.GET) on one method and @RequestMapping(method = RequestMethod.POST) on the other without path. misses path, so won't map correctly.

3. Final Answer:

   Use two methods with @RequestMapping(path = "/items", method = RequestMethod.GET) and @RequestMapping(path = "/items", method = RequestMethod.POST). -> Option A

4. Quick Check:

   Separate methods with same path, different HTTP methods [OK]

Hint: Map same path with different methods by specifying method attribute [OK]

Common Mistakes:

• Not specifying method attribute causing conflicts
• Checking HTTP method manually inside one method
• Omitting path attribute causing mapping errors