How to Solve CORS Issues in Flask Applications: Why \'Access-Control-Allow-Origin\' Headers are Necessary?

How to Solve CORS Issues in Flask Applications

When making cross-origin (CORS) requests, it's common to encounter errors due to missing 'Access-Control-Allow-Origin' headers. In this case, the request is being rejected because the server is not explicitly allowing requests from the client's origin.

To resolve this issue, you can enable CORS on the Flask application using the 'flask-cors' package. Here's how to do it:

1. Install flask-cors

   <code class="bash">pip install -U flask-cors</code>

   Copy after login

2. Import the Flask-CORS module

   <code class="python">from flask_cors import CORS, cross_origin</code>

   Copy after login

3. Configure CORS

   <code class="python">app = Flask(__name__)
   cors = CORS(app)
   app.config['CORS_HEADERS'] = 'Content-Type'</code>

   Copy after login

4. Decorate CORS Enabled Routes

   <code class="python">@app.route("/")
   @cross_origin()
   def helloWorld():
     return "Hello, cross-origin-world!"</code>

   Copy after login

In your specific case, you can modify your code as follows:

Client Code:

<code class="javascript">// Only change the crossDomain option to false
$.ajax({
  type: 'POST',
  url: 'http://...',
  data: "name=3&amp;email=3&amp;phone=3&amp;description=3",
  crossDomain: false,
  success: function(msg) {
      alert(msg);
  }
});</code>

Server Code:

<code class="python">from flask import Flask, request
from flask.ext.mandrill import Mandrill
from flask_cors import CORS

app = Flask(__name__)
cors = CORS(app)</code>

Note: Make sure to change the crossDomain option to false in the JavaScript code to prevent cross-domain requests. Also, ensure that your server configuration allows requests from the specified origin (http://...).

The above is the detailed content of How to Solve CORS Issues in Flask Applications: Why 'Access-Control-Allow-Origin' Headers are Necessary?. For more information, please follow other related articles on the PHP Chinese website!