Handling path variables and query params together in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to extract a path variable named 'id' in a Spring Boot controller method.

Spring Boot

@GetMapping("/items/[1]")
public String getItem(@PathVariable String id) {
    return "Item ID: " + id;
}

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

A/{id}

B/id

C{id}

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the curly braces around the variable name.

Using the variable name without slashes or braces.

The path variable must be enclosed in curly braces inside the URL pattern, like /{id}.

2fill in blank

medium

Complete the method parameter to extract a query parameter named 'filter' in a Spring Boot controller.

Spring Boot

public String getItems(@RequestParam(required = false) String [1]) {
    return "Filter: " + filter;
}

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

Avalue

Bid

Cfilter

Dparam

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different name than the query parameter.

Omitting the @RequestParam annotation.

The parameter name in the method must match the query parameter name, here 'filter'.

3fill in blank

hard

Fix the error in the annotation to correctly bind both path variable 'userId' and query parameter 'sort'.

Spring Boot

@GetMapping("/users/[1]")
public String getUser(@PathVariable String userId, @RequestParam String sort) {
    return userId + ": " + sort;
}

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

A/:userId

B/{userId}

C/userId

D/<userId>

Attempts:

3 left

💡 Hint

Common Mistakes

Using colon or angle brackets instead of curly braces.

Missing braces around the path variable.

Path variables must be enclosed in curly braces in the URL pattern.

4fill in blank

hard

Fill both blanks to define a method that handles path variable 'category' and optional query parameter 'page'.

Spring Boot

@GetMapping("/products/[1]")
public String listProducts(@PathVariable String [2], @RequestParam(required = false) Integer page) {
    return "Category: " + category + ", Page: " + page;
}

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

A{category}

Bcategory

Cpage

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatch between path variable name in URL and method parameter.

Forgetting curly braces in the URL.

The path variable in the URL must be {category} and the method parameter name must match category.

5fill in blank

hard

Fill all three blanks to create a method that handles path variables 'orderId' and 'itemId' and a query parameter 'status'.

Spring Boot

@GetMapping("/orders/[1]/items/[2]")
public String getOrderItem(@PathVariable String [3], @PathVariable String itemId, @RequestParam String status) {
    return "Order: " + orderId + ", Item: " + itemId + ", Status: " + status;
}

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

A{orderId}

BorderId

CitemId

D{itemId}

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names or missing curly braces in the URL.

Mismatch between method parameter names and path variable names.

The URL must have {orderId} and {itemId} as path variables. The method parameter for orderId must be named orderId.

Practice

1. In Spring Boot, which annotation is used to extract a value from the URL path segment in a controller method?

easy

A. @PathVariable

B. @RequestParam

C. @RequestBody

D. @RequestHeader

Solution

1. Step 1: Understand URL parts

   The URL path segment is the part of the URL that defines the resource location, like /users/{id}.

2. Step 2: Identify the correct annotation

   @PathVariable is used to bind a method parameter to a URI template variable in the path.

3. Final Answer:

   @PathVariable -> Option A

4. Quick Check:

   Path segment value = @PathVariable [OK]

Hint: Use @PathVariable for URL path parts, not query strings [OK]

Common Mistakes:

• Confusing @RequestParam with @PathVariable
• Using @RequestBody for path variables
• Trying to get path variables from headers

2. Which of the following method signatures correctly handles a path variable id and a query parameter sort in Spring Boot?

easy

A. public String getUser(@PathVariable String id, @RequestParam String sort)

B. public String getUser(@RequestParam String id, @PathVariable String sort)

C. public String getUser(@RequestParam String id, @RequestParam String sort)

D. public String getUser(@PathVariable String id, @PathVariable String sort)

Solution

1. Step 1: Match annotations to parameter types

   Path variables come from the URL path, so use @PathVariable for id. Query parameters come after ?, so use @RequestParam for sort.

2. Step 2: Check method signature correctness

   public String getUser(@PathVariable String id, @RequestParam String sort) correctly uses @PathVariable for id and @RequestParam for sort.

3. Final Answer:

   public String getUser(@PathVariable String id, @RequestParam String sort) -> Option A

4. Quick Check:

   Path variable = @PathVariable, Query param = @RequestParam [OK]

Hint: Path variables use @PathVariable, query params use @RequestParam [OK]

Common Mistakes:

• Swapping @PathVariable and @RequestParam
• Using @PathVariable for query parameters
• Missing one of the annotations

3. Given the controller method:

@GetMapping("/items/{itemId}")
public String getItem(@PathVariable String itemId, @RequestParam(defaultValue = "asc") String order) {
    return itemId + "-" + order;
}

What will be the output when a client requests /items/42?order=desc?

medium

A. "42-asc"

B. "42-desc"

C. "desc-42"

D. Runtime error due to missing parameter

Solution

1. Step 1: Identify values from URL

   Path variable itemId is "42" from /items/42. Query parameter order is "desc" from ?order=desc.

2. Step 2: Understand method return

   The method returns itemId + "-" + order, so "42-desc".

3. Final Answer:

   "42-desc" -> Option B

4. Quick Check:

   Path variable + query param = "42-desc" [OK]

Hint: Path variable fills {itemId}, query param fills order value [OK]

Common Mistakes:

• Ignoring query parameter and using default
• Mixing order of concatenation
• Expecting error when query param is present

4. Consider this controller method:

@GetMapping("/books/{bookId}")
public String getBook(@PathVariable int bookId, @RequestParam int page) {
    return "Book: " + bookId + ", Page: " + page;
}

What error will occur if a client calls /books/abc?page=2?

medium

A. 404 Not Found because path variable missing

B. 500 Internal Server Error due to null page

C. 400 Bad Request due to type mismatch

D. No error, returns "Book: abc, Page: 2"

Solution

1. Step 1: Check path variable type

   The method expects bookId as int, but URL provides "abc" which is not a number.

2. Step 2: Understand Spring Boot behavior on type mismatch

   Spring Boot returns 400 Bad Request when it cannot convert path variable to required type.

3. Final Answer:

   400 Bad Request due to type mismatch -> Option C

4. Quick Check:

   Type mismatch in @PathVariable causes 400 error [OK]

Hint: Non-numeric path variable for int causes 400 error [OK]

Common Mistakes:

• Expecting 404 Not Found instead of 400
• Assuming null page causes error
• Thinking method returns string with invalid input

5. You want to create a Spring Boot endpoint that handles a user ID as a path variable and optionally accepts a query parameter filter. If filter is missing, it should default to "all". Which method signature correctly implements this behavior?

hard

A. public String getUser(@PathVariable String userId, @RequestParam Optional<String> filter)

B. public String getUser(@RequestParam String userId, @RequestParam String filter)

C. public String getUser(@PathVariable String userId, @RequestParam(required = true) String filter)

D. public String getUser(@PathVariable String userId, @RequestParam(defaultValue = "all") String filter)

Solution

1. Step 1: Identify path variable usage

   User ID is part of the URL path, so use @PathVariable for userId.

2. Step 2: Handle optional query parameter with default

   Use @RequestParam with defaultValue = "all" to provide a default when filter is missing.

3. Final Answer:

   public String getUser(@PathVariable String userId, @RequestParam(defaultValue = "all") String filter) -> Option D

4. Quick Check:

   Default query param value = @RequestParam(defaultValue) [OK]

Hint: Use @RequestParam(defaultValue) for optional query params [OK]

Common Mistakes:

• Using @RequestParam(required = true) for optional params
• Using @RequestParam without defaultValue causing errors
• Confusing @RequestParam and @PathVariable roles