How to use Flask-CORS to achieve cross-domain resource sharing

How to use Flask-CORS to achieve cross-origin resource sharing

Introduction:
In network application development, cross-origin resource sharing (Cross Origin Resource Sharing, referred to as CORS) is a mechanism that allows servers to Share resources with specified sources or domain names. Using CORS, we can flexibly control data transmission between different domains and achieve safe and reliable cross-domain access. In this article, we will introduce how to use the Flask-CORS extension library to implement CORS functionality.

1. What is CORS
CORS is a security mechanism provided by the browser, which is used to control access to resources between different domains. In the traditional same-origin policy, browsers only allow web pages under the same domain name to interact, while CORS allows web pages under different domain names to initiate cross-domain requests. CORS is controlled through HTTP header fields and interacts between the client and server.

2. Introduction to Flask-CORS
Flask-CORS is a CORS extension library based on the Flask framework. It provides a simple and flexible solution for implementing CORS functions. Flask-CORS can control the behavior of CORS by setting parameters, such as allowed sources, request methods, request headers, etc.

3. Install Flask-CORS
You can use the pip command to install Flask-CORS:

pip install flask-cors

4. Use Flask-CORS
The following is a basic Flask application that demonstrates How to use Flask-CORS to achieve cross-domain resource sharing:

from flask import Flask, jsonify
from flask_cors import CORS

app = Flask(__name__)
CORS(app)  # 允许应用的所有视图都可以跨域访问

@app.route('/api/data', methods=['GET'])
def get_data():
    data = {
        'name': '小明',
        'age': 18,
        'gender': '男'
    }
    return jsonify(data)

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

In the above code, we first imported the Flask and flask_cors modules and created a Flask application. Next, use the CORS(app) statement to set all views of the application to be accessible across domains. Finally, we define a route that returns data in JSON format.

In actual development, we usually use more granular settings to flexibly control the CORS behavior of different views. Here's a more complex example:

from flask import Flask, jsonify
from flask_cors import CORS

app = Flask(__name__)
cors = CORS(app, resources={
    r"/*": {
        "origins": ["http://example.com", "http://www.example.com"],
        "methods": ["GET", "POST"],
        "headers": ["Content-Type", "Authorization"]
    }
})

@app.route('/api/data', methods=['GET'])
def get_data():
    data = {
        'name': '小明',
        'age': 18,
        'gender': '男'
    }
    return jsonify(data)

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

In the code above, we make more fine-grained settings by passing a resources parameter. In this example, we only allow requests from the two domain names example.com and www.example.com to initiate cross-domain access. We also specify the allowed request methods (GET and POST) and request headers (Content-Type and Authorization).

5. Summary
In this article, we introduced how to use the Flask-CORS extension library to achieve cross-domain resource sharing. By setting different parameters, we can flexibly control data transmission between different domains and achieve safe and reliable cross-domain access. CORS is a security mechanism provided by browsers, providing developers with more freedom and flexibility to meet the needs of different application scenarios.

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