Custom response headers in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a custom header named "X-Custom-Header" with value "Hello" to the response.

Spring Boot

return ResponseEntity.ok().header("X-Custom-Header", [1]).body("Success");

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

A"Hello"

BHello

C"X-Custom-Header"

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the header value

Using the header name as the value

Using a number instead of a string

The header value must be a string, so it needs to be in quotes like "Hello".

2fill in blank

medium

Complete the code to set the "Cache-Control" header to "no-cache" in the response.

Spring Boot

return ResponseEntity.ok().header("Cache-Control", [1]).body("Data");

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

A"no-cache"

B"cache"

C"private"

D"public"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect cache directives

Omitting quotes around the value

Using unrelated strings

The correct value to prevent caching is "no-cache" as a string.

3fill in blank

hard

Fix the error in the code to add a header "X-Rate-Limit" with value 100 as a string.

Spring Boot

return ResponseEntity.ok().header("X-Rate-Limit", [1]).body("Limit set");

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

A100

B"100"

CString.valueOf(100)

DInteger.toString(100)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a number instead of a string

Using methods that return strings but not as literals

Omitting quotes

Header values must be strings. Using "100" ensures the value is a string literal.

4fill in blank

hard

Fill both blanks to add header "X-App-Version" with value "1.0".

Spring Boot

return ResponseEntity.ok().header([1], [2]).body("Info");

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

A"X-App-Version"

B"1.0"

C"X-Env"

D"prod"

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping header names and values

Omitting quotes

Using wrong header names

The first blank is the header name "X-App-Version" and the second blank is its value "1.0".

5fill in blank

hard

Fill all three blanks to add headers "X-User" with value "admin", "X-Role" with value "editor", and "X-Status" with value "active".

Spring Boot

return ResponseEntity.ok()
  .header([1], [2])
  .header("X-Role", [3])
  .header("X-Status", "active")
  .body("User info");

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

A"X-User"

B"admin"

C"editor"

D"guest"

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up header names and values

Using wrong values

Forgetting quotes

The first header name is "X-User", its value is "admin", and the second header value is "editor" for "X-Role".

Practice

1. What is the main purpose of adding custom response headers in a Spring Boot application?

easy

A. To send extra information from the server to the client along with the response

B. To change the HTTP method of the request

C. To modify the request body before processing

D. To encrypt the response data automatically

Solution

1. Step 1: Understand what response headers do

   Response headers carry metadata or extra info about the response from server to client.

2. Step 2: Identify the purpose of custom headers

   Custom headers add extra info beyond standard headers, helping clients handle responses better.

3. Final Answer:

   To send extra information from the server to the client along with the response -> Option A

4. Quick Check:

   Custom headers = extra info sent [OK]

Hint: Custom headers add info to server replies, not change requests [OK]

Common Mistakes:

• Confusing headers with request body changes
• Thinking headers change HTTP methods
• Assuming headers encrypt data automatically

2. Which of the following is the correct way to add a custom header named X-Custom-Header with value 12345 using ResponseEntity in Spring Boot?

easy

A. return ResponseEntity.header("X-Custom-Header", "12345").body(data).ok();

B. return ResponseEntity.body(data).header("X-Custom-Header", "12345");

C. return ResponseEntity.ok().header("X-Custom-Header", "12345").body(data);

D. return ResponseEntity.setHeader("X-Custom-Header", "12345").body(data);

Solution

1. Step 1: Recall ResponseEntity builder pattern

   ResponseEntity.ok() starts building a 200 OK response, then header() adds headers, then body() sets the body.

2. Step 2: Check method chaining order

   Correct chaining is ResponseEntity.ok().header(...).body(...). Other orders or methods like setHeader() do not exist or cause errors.

3. Final Answer:

   return ResponseEntity.ok().header("X-Custom-Header", "12345").body(data); -> Option C

4. Quick Check:

   Use ok() then header() then body() [OK]

Hint: Start with ok(), then add header(), then body() [OK]

Common Mistakes:

• Calling header() after body()
• Using non-existent setHeader() method
• Wrong method chaining order

3. Given this Spring Boot controller method:

public ResponseEntity<String> getData() {
    return ResponseEntity.ok()
        .header("X-Rate-Limit", "1000")
        .header("X-Request-ID", "abc123")
        .body("Success");
}

What headers will the client receive in the response?

medium

A. No custom headers, only body 'Success'

B. Only X-Rate-Limit: 1000

C. Only X-Request-ID: abc123

D. X-Rate-Limit: 1000 and X-Request-ID: abc123

Solution

1. Step 1: Analyze header() calls in method

   Two header() calls add "X-Rate-Limit" with "1000" and "X-Request-ID" with "abc123".

2. Step 2: Confirm both headers are included in response

   ResponseEntity accumulates headers, so both custom headers are sent with the response.

3. Final Answer:

   X-Rate-Limit: 1000 and X-Request-ID: abc123 -> Option D

4. Quick Check:

   Multiple header() calls add multiple headers [OK]

Hint: Multiple header() calls add all headers to response [OK]

Common Mistakes:

• Assuming only last header() call applies
• Thinking headers overwrite each other
• Ignoring headers and focusing on body only

4. Identify the error in this Spring Boot code snippet that tries to add a custom header:

@GetMapping("/test")
public ResponseEntity<String> test() {
    ResponseEntity<String> response = ResponseEntity.ok();
    response.header("X-Test", "value");
    return response.body("Done");
}

medium

A. header() method does not exist on ResponseEntity

B. ResponseEntity.ok() returns an immutable object; header() does not modify it in place

C. body() cannot be called after header()

D. Missing @ResponseBody annotation

Solution

1. Step 1: Understand ResponseEntity immutability

   ResponseEntity.ok() returns a builder, but here it's assigned to ResponseEntity, which is immutable.

2. Step 2: header() returns a new builder; original is unchanged

   Calling header() on ResponseEntity does nothing; must chain calls on builder before building.

3. Final Answer:

   ResponseEntity.ok() returns an immutable object; header() does not modify it in place -> Option B

4. Quick Check:

   ResponseEntity is immutable; use builder chaining [OK]

Hint: Chain header() on builder, not on ResponseEntity instance [OK]

Common Mistakes:

• Trying to modify ResponseEntity after creation
• Confusing builder with built object
• Missing chaining of header() before body()

5. You want to add a custom header X-User-Status with value active only if a user is logged in, otherwise no header. Which is the best way to implement this in a Spring Boot controller method?

hard

A. Use ResponseEntity builder and conditionally call header() before body() based on login status

B. Always add header() with value "active" regardless of login status

C. Add header() after calling body() method

D. Modify HttpServletResponse directly without ResponseEntity

Solution

1. Step 1: Understand conditional header addition

   ResponseEntity builder allows conditional chaining of header() before body() to add headers only when needed.

2. Step 2: Avoid adding headers after body() or always adding unconditionally

   Adding header after body() is invalid; always adding ignores condition; modifying HttpServletResponse is less clean.

3. Final Answer:

   Use ResponseEntity builder and conditionally call header() before body() based on login status -> Option A

4. Quick Check:

   Conditionally chain header() before body() [OK]

Hint: Add headers conditionally before body() in ResponseEntity builder [OK]

Common Mistakes:

• Adding headers after body() call
• Ignoring login condition and always adding header
• Directly modifying HttpServletResponse instead of ResponseEntity