@PathVariable for URL parameters 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:

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

What will be the response body when a client requests /users/42?

Spring Boot

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

A User ID: 42

B User ID: {id}

C User ID: null

D 404 Not Found error

💡 Hint

The @PathVariable annotation binds the URL part to the method parameter.

The {id} in the URL path is captured and passed as the method parameter 'id'. So when the URL is /users/42, the method receives '42' as the id and returns 'User ID: 42'.

📝 Syntax

intermediate

Which option correctly uses @PathVariable with a different parameter name?

Given the URL pattern /items/{itemId}, which method signature correctly binds the path variable to a method parameter named id?

A

@GetMapping("/items/{itemId}")
public String getItem(@PathVariable("id") String id) { return id; }

B

@GetMapping("/items/{itemId}")
public String getItem(@PathVariable String itemId) { return id; }

C

@GetMapping("/items/{id}")
public String getItem(@PathVariable("itemId") String id) { return id; }

D

@GetMapping("/items/{itemId}")
public String getItem(@PathVariable("itemId") String id) { return id; }

💡 Hint

Use @PathVariable with the exact name of the path segment if the parameter name differs.

When the method parameter name differs from the path variable name, you must specify the path variable name inside @PathVariable("itemId"). Option D does this correctly.

🔧 Debug

advanced

What error occurs with this controller method?

Examine this Spring Boot controller method:

@GetMapping("/orders/{orderId}")
public String getOrder(@PathVariable int id) {
    return "Order: " + id;
}

What happens when a client requests /orders/123?

Spring Boot

@GetMapping("/orders/{orderId}")
public String getOrder(@PathVariable int id) {
    return "Order: " + id;
}

A HTTP 400 Bad Request due to type mismatch

B HTTP 400 Bad Request due to missing path variable binding

C HTTP 404 Not Found error

D Returns 'Order: 123' successfully

💡 Hint

Check if the method parameter name matches the path variable name or if @PathVariable specifies the name.

The path variable is named 'orderId' but the method parameter is 'id' without specifying @PathVariable("orderId"). Spring cannot bind the path variable to the parameter, causing a 400 Bad Request error.

❓ state_output

advanced

What is the output of this controller with multiple @PathVariable parameters?

Given this controller method:

@GetMapping("/books/{genre}/{id}")
public String getBook(@PathVariable String genre, @PathVariable int id) {
    return genre + "-" + id;
}

What is the response when the URL /books/scifi/7 is requested?

Spring Boot

@GetMapping("/books/{genre}/{id}")
public String getBook(@PathVariable String genre, @PathVariable int id) {
    return genre + "-" + id;
}

A books-scifi-7

B scifi-null

C scifi-7

D 7-scifi

💡 Hint

Each @PathVariable binds to the matching segment in the URL path.

The first path variable 'genre' gets 'scifi', and the second 'id' gets 7. The method returns 'scifi-7'.

🧠 Conceptual

expert

Which statement about @PathVariable is true?

Choose the correct statement about the use of @PathVariable in Spring Boot controllers.

A @PathVariable can bind multiple path segments separated by slashes into a single parameter using regex.

B @PathVariable requires the method parameter name to always match the path variable name in the URL.

C @PathVariable cannot be used with optional URL parameters.

D @PathVariable automatically converts path variables to any Java type without errors.

💡 Hint

Think about advanced usage of @PathVariable with patterns.

You can use regex in the path variable to capture multiple segments, e.g., @GetMapping("/files/{path:.+}") binds multiple path segments to 'path'.