@RequestParam for query strings in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to bind a query string parameter named 'name' to the method parameter.

Spring Boot

public String greet(@[1]("name") String userName) {
    return "Hello, " + userName + "!";
}

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

ARequestParam

BPathVariable

CAutowired

DRequestBody

Attempts:

3 left

💡 Hint

Common Mistakes

Using @PathVariable instead of @RequestParam for query parameters.

Forgetting to specify the parameter name inside the annotation.

The @RequestParam annotation binds a query string parameter to a method parameter in Spring Boot.

2fill in blank

medium

Complete the code to make the 'age' query parameter optional with a default value of 18.

Spring Boot

public String checkAge(@RequestParam(value = "age", required = [1], defaultValue = "18") int age) {
    return "Age is " + age;
}

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

Atrue

Bfalse

Cnull

Doptional

Attempts:

3 left

💡 Hint

Common Mistakes

Setting required to true when the parameter should be optional.

Not providing a defaultValue when required is false.

Setting required = false makes the query parameter optional. If missing, the default value is used.

3fill in blank

hard

Fix the error in the method parameter to correctly bind the 'id' query parameter as a Long.

Spring Boot

public String getUser(@RequestParam("id") [1] userId) {
    return "User ID: " + userId;
}

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

Aint

Bboolean

CString

DLong

Attempts:

3 left

💡 Hint

Common Mistakes

Using primitive int instead of Long for large IDs.

Using String when a numeric type is expected.

The query parameter 'id' should be bound to a Long type to match expected data.

4fill in blank

hard

Fill both blanks to bind two query parameters 'city' and 'country' with default values.

Spring Boot

public String location(@RequestParam(value = "city", defaultValue = [1]) String city, @RequestParam(value = "country", defaultValue = [2]) String country) {
    return city + ", " + country;
}

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

A"Unknown"

B"USA"

C"New York"

D"None"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes around default string values.

Mixing up city and country default values.

Default values are strings and must be quoted. Here, city defaults to "New York" and country to "USA".

5fill in blank

hard

Fill all three blanks to create a method that binds 'page', 'size', and 'sort' query parameters with defaults.

Spring Boot

public String listItems(@RequestParam(value = "page", defaultValue = [1]) int page, @RequestParam(value = "size", defaultValue = [2]) int size, @RequestParam(value = "sort", defaultValue = [3]) String sort) {
    return "Page: " + page + ", Size: " + size + ", Sort by: " + sort;
}

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

A"name"

B"id"

C"10"

D"1"

Attempts:

3 left

💡 Hint

Common Mistakes

Quoting numeric default values.

Using wrong default values for parameters.

Default values for page and size are numbers (1 and 10), and sort is a string ("id"). Numbers do not need quotes.

Practice

1. What does the @RequestParam annotation do in a Spring Boot controller?

easy

A. It maps the URL path to a controller method.

B. It extracts query string parameters from the URL and passes them to the method.

C. It defines the HTTP method type like GET or POST.

D. It handles exceptions thrown by the controller.

Solution

1. Step 1: Understand the role of @RequestParam

   @RequestParam is used to get values from the URL query string, like ?name=John.

2. Step 2: Compare with other annotations

   @RequestMapping maps URLs, @RequestParam extracts query parameters, others handle HTTP methods or errors.

3. Final Answer:

   It extracts query string parameters from the URL and passes them to the method. -> Option B

4. Quick Check:

   @RequestParam reads query parameters = A [OK]

Hint: Remember: @RequestParam reads URL query values [OK]

Common Mistakes:

• Confusing @RequestParam with @PathVariable
• Thinking it maps URLs instead of parameters
• Assuming it handles HTTP methods

2. Which of the following is the correct syntax to make a query parameter optional with a default value using @RequestParam?

easy

A. @RequestParam(value = "id", required = true, defaultValue = "0") int id

B. @RequestParam(name = "id", optional = true, default = 0) int id

C. @RequestParam(name = "id", required = false, defaultValue = "0") int id

D. @RequestParam("id", default = 0) int id

Solution

1. Step 1: Identify correct attributes for optional param

   To make a parameter optional, use required = false and provide defaultValue as a string.

2. Step 2: Check syntax correctness

   @RequestParam(name = "id", required = false, defaultValue = "0") int id uses required = false and defaultValue = "0" correctly; others use invalid attributes or miss required parts.

3. Final Answer:

   @RequestParam(name = "id", required = false, defaultValue = "0") int id -> Option C

4. Quick Check:

   Optional param syntax = A [OK]

Hint: Use required=false and defaultValue="value" for optional params [OK]

Common Mistakes:

• Using 'optional' instead of 'required'
• Setting defaultValue as a number instead of string
• Omitting required attribute

3. Given the controller method:

@GetMapping("/greet")
public String greet(@RequestParam String name) {
    return "Hello, " + name + "!";
}

What will be the output when accessing /greet?name=Anna?

medium

A. Hello, Anna!

B. Hello, null!

C. Hello, !

D. Error: Missing required parameter

Solution

1. Step 1: Understand @RequestParam behavior

   The method expects a query parameter 'name' which is required by default.

2. Step 2: Check the URL query string

   The URL provides ?name=Anna, so the method receives "Anna" as the parameter.

3. Final Answer:

   Hello, Anna! -> Option A

4. Quick Check:

   Query param 'name' = Anna, output greeting = D [OK]

Hint: If param is required and given, output uses it directly [OK]

Common Mistakes:

• Assuming missing param causes null instead of error
• Confusing query string with path variable
• Expecting default value without setting one

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

@GetMapping("/search")
public String search(@RequestParam int page) {
    return "Page: " + page;
}

What happens if the URL /search is accessed without any query parameters?

medium

A. The method returns "Page: 0"

B. The method returns "Page: null"

C. The method returns an empty string

D. The method throws a 400 Bad Request error

Solution

1. Step 1: Check @RequestParam default behavior

   By default, @RequestParam is required. Since 'page' is primitive int, it cannot be null.

2. Step 2: Analyze missing parameter effect

   Accessing /search without 'page' causes Spring to reject the request with 400 Bad Request due to missing required param.

3. Final Answer:

   The method throws a 400 Bad Request error -> Option D

4. Quick Check:

   Missing required param causes 400 error = C [OK]

Hint: Required params missing cause 400 error, primitives can't be null [OK]

Common Mistakes:

• Assuming default 0 for missing int param
• Expecting null for primitive types
• Thinking method returns empty string on error

5. You want to create a Spring Boot controller method that accepts an optional query parameter sort with default value "asc" and a required parameter page. Which method signature is correct?

hard

A. @GetMapping("/items")
public String items(@RequestParam(required = false, defaultValue = "asc") String sort, @RequestParam int page) { ... }

B. @GetMapping("/items")
public String items(@RequestParam(required = true, defaultValue = "asc") String sort, @RequestParam int page) { ... }

C. @GetMapping("/items")
public String items(@RequestParam(required = false) String sort, @RequestParam(required = true) int page) { ... }

D. @GetMapping("/items")
public String items(@RequestParam String sort = "asc", @RequestParam int page) { ... }

Solution

1. Step 1: Set optional param with default value

   Use required = false and defaultValue = "asc" for the optional 'sort' parameter.

2. Step 2: Ensure required param is declared correctly

   The 'page' parameter is required by default, so just @RequestParam int page is enough.

3. Step 3: Evaluate each option

   @GetMapping("/items") public String items(@RequestParam(required = false, defaultValue = "asc") String sort, @RequestParam int page) { ... } correctly combines required=false and defaultValue for 'sort' and required 'page'. Incorrect options include one with required=true and defaultValue (still required on missing), one with required=false without defaultValue (null on missing), and one with invalid syntax.

4. Final Answer:

   @GetMapping("/items") public String items(@RequestParam(required = false, defaultValue = "asc") String sort, @RequestParam int page) { ... } -> Option A

5. Quick Check:

   Optional with default + required param = B [OK]

Hint: Use required=false with defaultValue for optional params [OK]

Common Mistakes:

• Omitting required=false for optional param
• Trying to assign default value in method signature
• Forgetting defaultValue causes errors