Hey there! Let's get your Flask app set up to only accept text/plain requests and fix that annoying 500 error. Here's what's going wrong and how to fix it step by step:

问题根源 #

Right now, your code relies on request.get_json() which only works when the request has Content-Type: application/json. When a request comes in with any other content type (like text/plain), get_json() returns None—and trying to access data['kategori'] throws a KeyError, which triggers the 500 internal server error.

修复步骤 #

1. 强制验证Content-Type请求头 #

First, add a check to make sure incoming requests have the correct Content-Type header. If they don't, return a clear 400 Bad Request error instead of letting the app crash.

2. 正确读取text/plain请求体 #

Instead of get_json(), use request.get_data(as_text=True) to read the raw plain text content. How you parse this text depends on the format your clients will send—let's cover two common scenarios:

场景A：请求体是JSON格式但Content-Type为text/plain

If your clients are sending JSON strings but setting Content-Type: text/plain, you can manually parse the text into a Python dictionary:

from flask import Flask, request
from flask_restful import Api, Resource
from flask_cors import CORS
from flask_sqlalchemy import SQLAlchemy
import json

app = Flask(__name__)
api = Api(app)
cors = CORS(app)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///database.db'
db = SQLAlchemy(app)

class Priser(db.Model):
    pris = db.Column(db.Integer, primary_key=True)
    kategori = db.Column(db.Text)

class getPriser(Resource):
    def post(self):
        # 检查请求头是否为text/plain
        if request.content_type != 'text/plain':
            return {'error': 'Only Content-Type: text/plain is allowed'}, 400
        
        # 读取纯文本请求体
        raw_text = request.get_data(as_text=True)
        
        try:
            # 将纯文本解析为JSON格式
            data = json.loads(raw_text)
        except json.JSONDecodeError:
            return {'error': 'Invalid JSON format in plain text body'}, 400
        
        # 验证必要字段是否存在
        if 'kategori' not in data or 'pris' not in data:
            return {'error': 'Missing required fields: kategori and pris'}, 400
        
        # 确保pris是整数类型
        try:
            pris_value = int(data['pris'])
        except ValueError:
            return {'error': 'pris must be an integer'}, 400
        
        # 创建并保存数据库记录
        newPris = Priser(kategori=data['kategori'], pris=pris_value)
        db.session.add(newPris)
        db.session.commit()
        
        # 返回201状态码（符合RESTful最佳实践）
        return {'kategori': newPris.kategori, 'pris': newPris.pris}, 201

api.add_resource(getPriser, '/getpriser')

if __name__ == '__main__':
    with app.app_context():
        db.create_all()  # 确保启动时创建数据库表
    app.run(debug=True)

场景B：请求体是自定义纯文本格式（比如键值对）

If your clients send something like kategori=Electronics;pris=100 (a custom plain text format), replace the parsing part with this:

# 在getPriser的post方法中替换解析逻辑
raw_text = request.get_data(as_text=True)
data = {}
try:
    for pair in raw_text.split(';'):
        key, value = pair.split('=')
        data[key.strip()] = value.strip()
except ValueError:
    return {'error': 'Invalid plain text format. Use "kategori=xxx;pris=xxx"'}, 400

# 后续的字段验证和保存逻辑和上面一致

额外优化点 #

• Added explicit error handling for invalid formats and missing fields, so clients get clear feedback instead of generic 500 errors.
• Wrapped db.create_all() in an app context to ensure the database table is created correctly on app startup.
• Returned a 201 Created status code when the record is successfully added—this is standard for resource creation in REST APIs.

内容的提问来源于stack exchange，提问作者Kresten