Query parameter versioning in Rest API

Introduction

Query parameter versioning helps you manage different versions of an API by adding a version number in the URL query. This way, clients can ask for the version they want.

When you want to keep old API versions working while adding new features.

When clients need to choose which API version to use without changing the URL path.

When you want a simple way to test new API versions without breaking existing users.

Syntax

Rest API

GET /api/resource?version=1
GET /api/resource?version=2

The version is passed as a query parameter, usually named version.

This method keeps the base URL the same and only changes the query part.

Examples

Request users using version 1 of the API.

Rest API

GET /users?version=1

Request users using version 2 of the API with new features.

Rest API

GET /users?version=2

Request products list from version 1.

Rest API

GET /products?version=1

Sample Program

This simple Flask app shows how to use query parameter versioning. It checks the version parameter and returns different data based on it.

Rest API

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/api/data')
def get_data():
    version = request.args.get('version', '1')
    if version == '1':
        return jsonify({'message': 'This is version 1 data'})
    elif version == '2':
        return jsonify({'message': 'This is version 2 data with extra info', 'extra': 123})
    else:
        return jsonify({'error': 'Version not supported'}), 400

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Query parameter versioning is easy to implement but can clutter URLs if many parameters are used.

Clients must remember to add the version parameter to get the right API version.

It works well when you want to keep the URL path clean and use parameters for version control.

Summary

Query parameter versioning uses a URL query like ?version=1 to select API versions.

It helps keep old and new API versions available without changing the main URL path.

Clients specify the version they want by adding the version number in the query string.

Practice

1. What is the main purpose of using query parameter versioning in REST APIs?

easy

A. To change the main URL path for each API version

B. To allow clients to specify which API version they want using a query string

C. To hide the API version from clients

D. To force all clients to use the latest API version only

Solution

1. Step 1: Understand query parameter versioning concept

   Query parameter versioning lets clients add a version number in the URL query string, like ?version=1.

2. Step 2: Identify the purpose of this method

   This allows clients to choose which API version to use without changing the main URL path.

3. Final Answer:

   To allow clients to specify which API version they want using a query string -> Option B

4. Quick Check:

   Query parameter versioning = client selects version [OK]

Hint: Version in query string means client chooses API version [OK]

Common Mistakes:

• Thinking versioning changes the main URL path
• Assuming versioning hides API versions
• Believing all clients must use latest version only

2. Which of the following is the correct way to request version 2 of an API using query parameter versioning?

easy

A. GET /api/resource/version=2

B. GET /api/version/2/resource

C. GET /api/resource?version=2

D. GET /api/resource#version=2

Solution

1. Step 1: Recall query parameter syntax in URLs

   Query parameters come after a question mark ? and use key=value pairs, e.g., ?version=2.

2. Step 2: Match the correct syntax for versioning

   The correct way to specify version 2 is by adding ?version=2 after the resource path.

3. Final Answer:

   GET /api/resource?version=2 -> Option C

4. Quick Check:

   Query param syntax = ?key=value [OK]

Hint: Query parameters start with ? and use key=value [OK]

Common Mistakes:

• Using slashes instead of query parameters
• Using # instead of ? for query parameters
• Placing version inside the URL path incorrectly

3. Given this API endpoint code snippet handling versioning:

def get_data(request):
    version = request.GET.get('version', '1')
    if version == '1':
        return 'Data from v1'
    elif version == '2':
        return 'Data from v2'
    else:
        return 'Unknown version'

What will be the output if the client calls /api/data?version=2?

medium

A. "Data from v2"

B. "Unknown version"

C. "Data from v1"

D. Error: version parameter missing

Solution

1. Step 1: Extract version from query parameters

   The code gets the version from the query string. If missing, it defaults to '1'. Here, version='2'.

2. Step 2: Check version conditions

   Since version is '2', the code returns 'Data from v2'.

3. Final Answer:

   "Data from v2" -> Option A

4. Quick Check:

   version=2 returns v2 data [OK]

Hint: Check query param value matches version condition [OK]

Common Mistakes:

• Assuming default version is always used
• Confusing string and integer comparison
• Expecting error when version is provided

4. Consider this code snippet for versioning:

def api_handler(request):
    version = request.GET['version']
    if version == '1':
        return 'Version 1'
    else:
        return 'Other version'

What error will occur if the client calls /api/data without a version parameter?

medium

A. KeyError because 'version' key is missing

B. SyntaxError in code

C. Returns 'Version 1' by default

D. Returns 'Other version'

Solution

1. Step 1: Understand how version is accessed

   The code uses request.GET['version'] which raises KeyError if 'version' is missing.

2. Step 2: Analyze call without version parameter

   Calling without ?version=... means 'version' key is missing, causing KeyError.

3. Final Answer:

   KeyError because 'version' key is missing -> Option A

4. Quick Check:

   Missing key access causes KeyError [OK]

Hint: Access query keys safely to avoid KeyError [OK]

Common Mistakes:

• Assuming default version is used automatically
• Expecting no error when parameter is missing
• Confusing KeyError with SyntaxError

5. You want to support versions 1 and 2 of your API using query parameter versioning. Version 1 returns a list of users as strings, and version 2 returns a list of user objects with 'name' and 'id'. Which approach correctly handles this in a single endpoint?

hard

A. Return an error if version parameter is missing or unknown

B. Change the URL path to /v1/users and /v2/users instead of query parameters

C. Ignore the version parameter and always return the latest format

D. Use ?version=1 to return ['Alice', 'Bob'], and ?version=2 to return [{'name':'Alice','id':1},{'name':'Bob','id':2}]

Solution

1. Step 1: Understand query parameter versioning usage

   Clients specify version using ?version=1 or ?version=2 in the same URL.

2. Step 2: Return different data formats based on version

   Return simple list of strings for version 1, and detailed objects for version 2, matching client request.

3. Final Answer:

   Use ?version=1 to return ['Alice', 'Bob'], and ?version=2 to return [{'name':'Alice','id':1},{'name':'Bob','id':2}] -> Option D

4. Quick Check:

   Query param version controls response format [OK]

Hint: Return data format based on version query param [OK]

Common Mistakes:

• Changing URL path instead of using query parameters
• Ignoring version parameter and mixing formats
• Returning errors unnecessarily for missing versions