Request body structure in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the request body in a REST API?

The request body carries the data sent from the client to the server, usually when creating or updating resources.

beginner

Name two common formats used for the request body in REST APIs.

JSON (JavaScript Object Notation) and XML (eXtensible Markup Language) are common formats for request bodies.

beginner

Why is it important to set the 'Content-Type' header when sending a request body?

The 'Content-Type' header tells the server the format of the data in the request body, so it can parse it correctly.

intermediate

What happens if you send a request body with a GET request?

Typically, GET requests do not have a request body. Sending one may be ignored or cause unexpected behavior.

beginner

How do you structure a JSON request body to create a new user with name and email?

You create a JSON object with keys and values, for example: {"name": "Alice", "email": "[e-mail]"}.

What header must you include to tell the server the format of the request body?

A Accept

B User-Agent

C Authorization

D Content-Type

The Content-Type header specifies the media type of the request body.

Which HTTP method usually includes a request body?

A DELETE

B GET

C POST

D HEAD

POST requests commonly include a request body to send data to the server.

What is the most common format for request bodies in REST APIs?

A JSON

B CSV

C HTML

D Plain text

JSON is widely used because it is easy to read and write for humans and machines.

If you forget to set the Content-Type header, what might happen?

A Server may not parse the request body correctly

B Server rejects the request immediately

C Request body is ignored but server responds normally

D Client automatically sets the header

Without Content-Type, the server may not understand how to read the request body.

Which of these is a valid JSON request body to update a user's age to 30?

A age=30

B {"age": 30}

C ["age", 30]

D {age: 30}

Valid JSON requires keys in double quotes and proper syntax.

Explain what a request body is and why it is used in REST APIs.

Think about when you fill a form and send it to a website.

Describe how to properly format a JSON request body and what headers to include.

Remember the curly braces and quotes in JSON.

Practice

1. What is the main purpose of the request body in a REST API POST request?

easy

A. To define the HTTP method used

B. To send data from the client to the server

C. To specify the URL of the API endpoint

D. To set the server response status code

Solution

1. Step 1: Understand the role of request body

   The request body contains the data sent by the client to the server, usually in POST or PUT requests.

2. Step 2: Differentiate from other parts of the request

   The URL specifies the endpoint, the method defines the action, and the status code is part of the response, not the request body.

3. Final Answer:

   To send data from the client to the server -> Option B

4. Quick Check:

   Request body = data sent to server [OK]

Hint: Request body carries data sent to server in POST/PUT [OK]

Common Mistakes:

• Confusing request body with URL or headers
• Thinking request body sets HTTP method
• Mixing request body with response status

2. Which of the following is the correct way to indicate JSON data in the request body header?

easy

A. Content-Type: text/plain

B. Content-Type: application/xml

C. Content-Type: application/json

D. Content-Type: multipart/form-data

Solution

1. Step 1: Identify the header for JSON data

   The header Content-Type: application/json tells the server the body contains JSON formatted data.

2. Step 2: Compare with other content types

   text/plain is plain text, multipart/form-data is for file uploads, and application/xml is for XML data.

3. Final Answer:

   Content-Type: application/json -> Option C

4. Quick Check:

   JSON header = application/json [OK]

Hint: Use application/json for JSON request bodies [OK]

Common Mistakes:

• Using text/plain for JSON data
• Forgetting to set Content-Type header
• Using multipart/form-data without files

3. Given this JSON request body sent to an API:

{
  "name": "Alice",
  "age": 30
}

What will the server receive as the value of age?

medium

A. Undefined

B. "30" (string)

C. null

D. 30 (number)

Solution

1. Step 1: Analyze the JSON data types

   The value for age is written as 30 without quotes, so it is a number, not a string.

2. Step 2: Understand server parsing

   The server parses JSON and keeps numbers as numbers, so age will be the number 30.

3. Final Answer:

   30 (number) -> Option D

4. Quick Check:

   Unquoted numbers in JSON = number type [OK]

Hint: Numbers in JSON have no quotes, so parsed as numbers [OK]

Common Mistakes:

• Assuming all JSON values are strings
• Confusing number and string types
• Ignoring JSON parsing rules

4. You send this request body:

{
  "username": "bob",
  "password": "1234"
}

But the server returns a 400 Bad Request error. What is a likely cause?

medium

A. Missing Content-Type header or wrong format

B. The username is too short

C. The password is numeric

D. The request method is GET

Solution

1. Step 1: Check request headers and format

   A 400 Bad Request often means the server cannot parse the body, commonly due to missing or incorrect Content-Type header.

2. Step 2: Evaluate other options

   Username length or password content usually cause validation errors, not 400 errors. GET requests do not have bodies, but the question implies a body was sent.

3. Final Answer:

   Missing Content-Type header or wrong format -> Option A

4. Quick Check:

   400 error often = bad or missing Content-Type [OK]

Hint: Always set correct Content-Type header to avoid 400 errors [OK]

Common Mistakes:

• Ignoring Content-Type header
• Assuming 400 means validation error
• Confusing GET with POST request body

5. You want to send a nested JSON object in the request body to create a user with address info:

{
  "name": "Eve",
  "address": {
    "street": "123 Main St",
    "city": "Townsville"
  }
}

Which Content-Type header and body format should you use to ensure the server correctly understands this nested data?

hard

A. Content-Type: application/json with the JSON body as shown

B. Content-Type: text/plain with JSON body as string

C. Content-Type: application/x-www-form-urlencoded with nested keys

D. Content-Type: multipart/form-data with JSON inside a file

Solution

1. Step 1: Identify correct header for nested JSON

   Nested JSON requires application/json Content-Type so the server parses the structure correctly.

2. Step 2: Evaluate other formats

   text/plain treats body as plain text, application/x-www-form-urlencoded does not support nested objects well, and multipart/form-data is for files, not nested JSON.

3. Final Answer:

   Content-Type: application/json with the JSON body as shown -> Option A

4. Quick Check:

   Nested JSON needs application/json header [OK]

Hint: Use application/json header for nested JSON objects [OK]

Common Mistakes:

• Using form-urlencoded for nested JSON
• Sending JSON as plain text without header
• Uploading JSON as file instead of body