Self link for current resource in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this REST API self link generation code?

Given the following Python Flask code snippet that generates a self link for a resource, what is the output when accessing the endpoint /items/42?

Rest API

from flask import Flask, url_for, jsonify, request
app = Flask(__name__)

@app.route('/items/<int:item_id>')
def get_item(item_id):
    self_url = url_for('get_item', item_id=item_id, _external=True)
    return jsonify({'id': item_id, 'self': self_url})

with app.test_request_context():
    print(url_for('get_item', item_id=42, _external=True))

A "http://localhost/items/42"

B "/items/42"

C "http://localhost/items?id=42"

D "http://localhost/items/"

💡 Hint

Look at the _external=True parameter in url_for to understand the full URL generation.

The url_for function with _external=True generates the full URL including the scheme and host. The route uses a path parameter, so the URL includes /items/42.

🧠 Conceptual

intermediate

Which HTTP header is commonly used to indicate the self link of a resource in REST APIs?

In REST API design, which HTTP header is typically used to provide the URL of the current resource (self link) in the response headers?

A Content-Location

B Location

C Link

D Self

💡 Hint

Think about headers that can contain multiple URLs with relation types.

The Link header can include URLs with relation types such as rel="self" to indicate the self link of the resource.

🔧 Debug

advanced

Why does this code fail to generate a correct self link?

Consider this Node.js Express code snippet intended to add a self link to a JSON response. Why does it fail to produce the correct full URL for the self link?

Rest API

app.get('/users/:id', (req, res) => {
  const selfLink = `${req.protocol}://${req.hostname}/users/${req.params.id}`;
  res.json({ id: req.params.id, self: selfLink });
});

A req.protocol is undefined in Express, causing an error

B The template string syntax is incorrect

C req.params.id is not accessible in this route

D req.hostname does not include the port, so the URL may be incomplete

💡 Hint

Check how Express provides host and port information in requests.

req.hostname returns only the hostname without the port. If the server runs on a non-default port, the generated URL misses the port, making the self link incomplete.

📝 Syntax

advanced

Which option correctly adds a self link in a JSON response in Java Spring Boot?

Given a Spring Boot controller method, which code snippet correctly adds a self link to the returned resource using Spring HATEOAS?

Rest API

@GetMapping("/books/{id}")
public EntityModel<Book> getBook(@PathVariable Long id) {
    Book book = bookRepository.findById(id).orElseThrow();
    // Add self link here
}

A return EntityModel.of(book, linkTo(methodOn(BookController.class).getBook(id)).withSelfRel());

B return new EntityModel<>(book, new Link("/books/" + id));

C return ResponseEntity.ok(book).header("self", "/books/" + id).build();

D return book.add(linkTo(BookController.class).slash(id).withSelfRel());

💡 Hint

Look for the standard way to create self links with Spring HATEOAS using methodOn and linkTo.

Option A uses EntityModel.of with linkTo and methodOn to create a self link properly. Other options either misuse classes or headers.

🚀 Application

expert

How many items are in the resulting JSON when adding a self link to a nested resource?

Consider this JSON response for a REST API resource with a nested subresource and self links added at both levels: { "id": 10, "name": "Folder", "self": "http://api.example.com/folders/10", "files": [ { "id": 5, "filename": "doc.txt", "self": "http://api.example.com/folders/10/files/5" } ] } How many total keys are at the top level of the JSON object?

A 3

B 4

C 5

D 6

💡 Hint

Count the keys directly inside the outermost curly braces.

The top-level keys are: id, name, self, and files. That makes 4 keys total.