@PathVariable for URL parameters in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to bind the URL parameter to the method argument.

Spring Boot

@GetMapping("/users/{id}")
public String getUser(@[1] String id) {
    return "User ID: " + id;
}

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

ARequestHeader

BRequestParam

CRequestBody

DPathVariable

Attempts:

3 left

💡 Hint

Common Mistakes

Using @RequestParam instead of @PathVariable

Forgetting to add the annotation

Using @RequestBody for URL parameters

The @PathVariable annotation binds the URL path parameter {id} to the method argument.

2fill in blank

medium

Complete the code to specify the path variable name explicitly.

Spring Boot

@GetMapping("/products/{productId}")
public String getProduct(@PathVariable("[1]") String id) {
    return "Product ID: " + id;
}

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

Aid

Bpid

CproductId

Dproduct

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name than the URL path variable

Omitting the annotation parameter when names differ

The string inside @PathVariable must match the name in the URL path {productId}.

3fill in blank

hard

Fix the error in the method parameter to correctly bind the path variable.

Spring Boot

@GetMapping("/orders/{orderId}")
public String getOrder(@PathVariable("[1]") String id) {
    return "Order ID: " + id;
}

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

AorderId

B(orderId)

C"orderId"

D("orderId")

Attempts:

3 left

💡 Hint

Common Mistakes

Missing parentheses

Missing quotes around the variable name

Using variable name without quotes

The @PathVariable annotation requires the path variable name as a string in parentheses.

4fill in blank

hard

Fill both blanks to create a method that binds two path variables.

Spring Boot

@GetMapping("/users/{userId}/posts/{postId}")
public String getPost(@PathVariable("[1]") String user, @PathVariable("[2]") String post) {
    return "User: " + user + ", Post: " + post;
}

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

AuserId

Bpost

CpostId

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the path variable names

Using variable names instead of path variable names

Each @PathVariable must match the corresponding name in the URL path.

5fill in blank

hard

Fill all three blanks to create a method that binds three path variables with explicit names.

Spring Boot

@GetMapping("/shops/{shopId}/categories/{categoryId}/items/{itemId}")
public String getItem(@PathVariable("[1]") String shop, @PathVariable("[2]") String category, @PathVariable("[3]") String item) {
    return "Shop: " + shop + ", Category: " + category + ", Item: " + item;
}

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

AshopId

BcategoryId

CitemId

Ditem

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names instead of path variable names

Mixing up the order of path variables

Each @PathVariable annotation must match the corresponding path variable name in the URL.

Practice

1. What is the main purpose of the @PathVariable annotation in Spring Boot?

easy

A. To bind form data to a Java object

B. To handle exceptions in controller methods

C. To define a fixed URL mapping for a controller method

D. To extract values from the URL path and pass them as method parameters

Solution

1. Step 1: Understand the role of @PathVariable

   @PathVariable is used to get dynamic parts of the URL and pass them to method parameters.

2. Step 2: Compare with other annotations

   Other options like binding form data or exception handling are done by different annotations, not @PathVariable.

3. Final Answer:

   To extract values from the URL path and pass them as method parameters -> Option D

4. Quick Check:

   @PathVariable = extract URL values [OK]

Hint: Remember: @PathVariable grabs values directly from URL path [OK]

Common Mistakes:

• Confusing @PathVariable with @RequestParam
• Thinking it binds form data
• Assuming it handles exceptions

2. Which of the following is the correct syntax to use @PathVariable in a Spring Boot controller method to get an id from the URL /user/{id}?

easy

A. @GetMapping("/user/{id}") public String getUser(@PathVariable int id) { ... }

B. @GetMapping("/user") public String getUser(@PathVariable int id) { ... }

C. @GetMapping("/user/{id}") public String getUser(@RequestParam int id) { ... }

D. @GetMapping("/user/{id}") public String getUser(@PathVariable String name) { ... }

Solution

1. Step 1: Match URL pattern with method parameter

   The URL has {id}, so the method must have @PathVariable int id to match the placeholder.

2. Step 2: Check annotation and parameter type

   @GetMapping("/user/{id}") public String getUser(@PathVariable int id) { ... } correctly uses @PathVariable with int id and matches the URL pattern.

3. Final Answer:

   @GetMapping("/user/{id}") public String getUser(@PathVariable int id) { ... } -> Option A

4. Quick Check:

   URL {id} matches @PathVariable int id [OK]

Hint: URL placeholder and @PathVariable name must match [OK]

Common Mistakes:

• Missing {id} in URL path
• Using @RequestParam instead of @PathVariable
• Mismatching parameter name and URL placeholder

3. Given the following Spring Boot controller method:

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

What will be the output when a client requests /product/electronics/42?

medium

A. electronics-42

B. 42-electronics

C. category-id

D. electronics42

Solution

1. Step 1: Identify parameter values from URL

   URL /product/electronics/42 means category = "electronics", id = 42.

2. Step 2: Understand return statement

   The method returns category + "-" + id, so it returns "electronics-42".

3. Final Answer:

   electronics-42 -> Option A

4. Quick Check:

   Return = category + "-" + id = electronics-42 [OK]

Hint: Match URL parts to parameters in order [OK]

Common Mistakes:

• Swapping parameter order
• Ignoring the dash '-' in return
• Confusing @PathVariable with @RequestParam

4. Consider this Spring Boot controller method:

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

What will happen when a client requests /order/100?

medium

A. Returns "Order: 0"

B. Returns "Order: 100"

C. Throws an error because parameter name does not match path variable

D. Returns null

Solution

1. Step 1: Check URL placeholder and method parameter names

   URL has {orderId}, but method parameter is named id without specifying name in @PathVariable.

2. Step 2: Understand default matching behavior

   Without specifying the name in @PathVariable, Spring tries to match parameter name to path variable name. They differ, causing an error.

3. Final Answer:

   Throws an error because parameter name does not match path variable -> Option C

4. Quick Check:

   Parameter name must match path variable or specify name [OK]

Hint: Parameter name must match path variable or use @PathVariable("name") [OK]

Common Mistakes:

• Assuming names can differ without annotation
• Ignoring the need to specify variable name in @PathVariable
• Expecting default value assignment

5. You want to create a Spring Boot controller method that handles URLs like /blog/{year}/{month}/{slug} where year and month are integers and slug is a string. Which of the following method signatures correctly uses @PathVariable to extract these values?

hard

A. @GetMapping("/blog/{year}/{month}/{slug}")
public String getPost(@PathVariable int yr, @PathVariable int mo, @PathVariable String sl) { ... }

B. @GetMapping("/blog/{year}/{month}/{slug}")
public String getPost(@PathVariable("year") int y, @PathVariable("month") int m, @PathVariable("slug") String s) { ... }

C. @GetMapping("/blog/{year}/{month}/{slug}")
public String getPost(@PathVariable String year, @PathVariable String month, @PathVariable String slug) { ... }

D. @GetMapping("/blog/{year}/{month}/{slug}")
public String getPost(@PathVariable int y, @PathVariable int m, @PathVariable String s) { ... }

Solution

1. Step 1: Match URL placeholders with method parameters

   The URL has {year}, {month}, {slug}. Method parameters must match these names or specify them explicitly.

2. Step 2: Check parameter names and @PathVariable usage

   @GetMapping("/blog/{year}/{month}/{slug}") public String getPost(@PathVariable("year") int y, @PathVariable("month") int m, @PathVariable("slug") String s) { ... } uses different parameter names (y, m, s) but explicitly maps them to URL placeholders using @PathVariable("name"), which is correct.

3. Final Answer:

   @GetMapping("/blog/{year}/{month}/{slug}") public String getPost(@PathVariable("year") int y, @PathVariable("month") int m, @PathVariable("slug") String s) { ... } -> Option B

4. Quick Check:

   Explicit name mapping allows different parameter names [OK]

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

Common Mistakes:

• Using mismatched parameter names without specifying name
• Using wrong data types for year/month
• Assuming parameter names must always match URL placeholders