I have been trying to serialize an SQLAlchemy model so that I can pass a number of data from flask server to an html socketio client.
I am trying the following where an object is frirst converted into a dictionary and then jsonified. However, this is not working. I am getting the following error message at the designated line:
TypeError: Object of type Response is not JSON serializable
How can achieve what I need?
app.py
from flask import Flask, render_template, jsonify
from flask_marshmallow import Marshmallow
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
import secrets
import string
import logging
from flask_socketio import SocketIO, emit
import os
import subprocess
async_mode = None
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///filename.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
socketio_obj = SocketIO(app)
class JobQueue(db.Model):
__tablename__ = 'job_queue'
job_id = db.Column(db.Integer, primary_key=True)
unique_job_key = db.Column(db.String(64), index=True)
user_name = db.Column(db.String, index=True)
input_string = db.Column(db.String(256))
is_done = db.Column(db.Boolean)
created_at = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
def to_dictionary(self):
return {
"job_id": self.job_id,
"unique_job_key": self.unique_job_key,
"user_name": self.user_name,
"input_string": self.input_string,
"is_done": self.is_done,
"created_at": self.created_at
}
# end function
# end class
def get_data():
users = JobQueue.query.order_by(JobQueue.created_at).all()
return users
def get_serialized_data():
all_users = get_data()
returns = [item.to_dictionary() for item in all_users]
return jsonify(all_users = returns)
... ... ... ... ... ... ... ...
@socketio_obj.on('first_connect_event', namespace='/test')
def handle_first_connect_event(arg1):
try:
msg = arg1['first_message']
print(msg)
users = get_serialized_data()
emit('get_data', {'users': users}) #<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
except Exception as ex:
logging.exception("")
print(ex)
The full error trace:
ERROR:root:
Traceback (most recent call last):
File "C:\git\funkclusterfrontend\app.py", line 106, in handle_first_connect_event
emit('get_data', {'users': users})
File "C:\ProgramData\Miniconda3\lib\site-packages\flask_socketio\__init__.py", line 899, in emit
return socketio.emit(event, *args, namespace=namespace, to=to,
File "C:\ProgramData\Miniconda3\lib\site-packages\flask_socketio\__init__.py", line 460, in emit
self.server.emit(event, *args, namespace=namespace, to=to,
File "C:\ProgramData\Miniconda3\lib\site-packages\socketio\server.py", line 294, in emit
self.manager.emit(event, data, namespace, room=room,
File "C:\ProgramData\Miniconda3\lib\site-packages\socketio\base_manager.py", line 167, in emit
self.server._emit_internal(eio_sid, event, data, namespace, id)
File "C:\ProgramData\Miniconda3\lib\site-packages\socketio\server.py", line 612, in _emit_internal
self._send_packet(eio_sid, packet.Packet(
File "C:\ProgramData\Miniconda3\lib\site-packages\socketio\server.py", line 617, in _send_packet
encoded_packet = pkt.encode()
File "C:\ProgramData\Miniconda3\lib\site-packages\socketio\packet.py", line 61, in encode
encoded_packet = self.json.dumps(data, separators=(',', ':'))
File "C:\ProgramData\Miniconda3\lib\json\__init__.py", line 234, in dumps
return cls(
File "C:\ProgramData\Miniconda3\lib\json\encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "C:\ProgramData\Miniconda3\lib\json\encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "C:\ProgramData\Miniconda3\lib\json\encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type Response is not JSON serializable
Object of type Response is not JSON serializable
CodePudding user response：
The jsonify() function is used to create responses in Flask endpoints, it should never be used when emitting data using Flask-SocketIO.
In Flask-SocketIO, the data that you send must be passed as a dictionary. The conversion to JSON is automatically handled by the extension.
To fix this, change the get_serialized_data() function to return the list of users as a list of Python dictionaries:
def get_serialized_data():
all_users = get_data()
return [item.to_dictionary() for item in all_users]
In addition, you should make sure that your to_dictionary() method only uses JSON-friendly types. The created_at field should be converted to a string to work with JSON.
Once you fix these two problems, I think your emit should serialize without errors.
CodePudding user response：
I solved this serialization problem in the following way:
- converted the dictionary into a JSON
- converted the JSON into string
- transmitted the string from server to client
- on the cient side, converted the string into JSON again
This is how I was able to skip Marshmallow and other similar libraries.
My code looks as follows:
Server side
def get_serialized_data():
all_users = get_data()
dictionary = [item.to_dictionary() for item in all_users]
json_object = json.dumps(dictionary, indent=4, sort_keys=True, default=str)
return len(all_users), json_object
@socketio_obj.on('first_connect_event', namespace='/test')
def handle_first_connect_event(arg1):
try:
msg = arg1['first_message']
print(msg)
rows, users = get_serialized_data()
print(rows)
# print(users)
emit('get_data', {'rows': str(rows), 'users': str(users)})
except Exception as ex:
logging.exception("")
print(ex)
Client side
socket.on('get_data', function (msg){
let row_count = msg['rows'];
let json_users = $.parseJSON(msg['users']);
create_table(row_count, json_users);
});
function create_table(row_count, json_users)
{
let table_body = $("#table1 tbody");
table_body.empty();
let markup = '';
for(let i=0 ; i<row_count ; i )
{
markup = "<tr>"
"<td>" json_users[i]['job_id'] "</td>"
"<td>" json_users[i]['unique_job_key'] "</td>"
"<td>" json_users[i]['user_name'] "</td>"
"<td>" json_users[i]['input_string'] "</td>"
"<td>" json_users[i]['is_done'] "</td>"
"<td>" json_users[i]['created_at'] "</td>"
"</tr>";
table_body.append(markup);
}
}