Flask开发随机密码生成器出现JSONDecodeError与405错误排查

返回405状态码、后续触发JSON解析错误是服务端路由配置、代码逻辑、客户端请求配置多处错误共同导致的，核心问题点如下：

• 路由拼写错误是405的直接诱因：服务端注册路由时写的是'/api/ PyPassword_generator'，/api/后多了一个多余空格，实际生效的路由带空格，和客户端请求的/api/PyPassword_generator路径不匹配，Flask找不到对应接口就返回405的HTML错误页，客户端拿HTML内容调用.json()方法自然会触发JSON解码失败。
• 服务端监听配置和客户端请求地址不匹配：服务端启动时监听的是10.0.0.10:5000，客户端发请求的目标地址是127.0.0.1:1337，即便路由正确也无法正常连通。
• 代码结构错误：密码生成的逻辑块缩进错误，被写到了run()方法内部，接口里调用的self.test(a,b,c)方法根本不存在，密码生成逻辑没有被定义为可调用的类方法。
• 接口返回值缺失：接口内调用jsonify()生成响应后没有加return关键字，逻辑跑通也无法给客户端返回正确的JSON数据。
• HTTP方法写法不规范：路由的methods参数里写的是'Get'，Flask要求HTTP方法名必须全大写，正确写法为'GET'。
• 传参顺序错误：实例化服务端类时，第二个位置传的是数字列表、第三个位置传的是符号列表，和类初始化方法接收的symbols、numbers参数顺序相反，会导致生成的密码字符类型不符合预期。
• 客户端判断逻辑错误：if r: break的判断逻辑完全写反，requests库中只要服务端返回响应（哪怕是4xx/5xx错误），响应对象的布尔值都是True，会直接跳出循环，根本走不到后续响应解析的步骤。

1. 修正后的服务端代码 #

from flask import Flask, request, jsonify
import random

class game:
    def __init__(self,letters,symbols,numbers):
        self.letters=letters
        self.symbols=symbols
        self.numbers=numbers
        self.app = Flask("Shmuel Api server",static_url_path='')
        self.app.secret_key="Secret"

        # 去掉路由多余空格，HTTP方法改为全大写
        @self.app.route('/api/PyPassword_generator', methods=['GET',"POST"])
        def PyPassword_generator():
            a=int(request.json["letters"])
            b=int(request.json["symbols"])
            c=int(request.json["numbers"])
            password = self.generate_pwd(a,b,c)
            # 补充return关键字返回JSON响应
            return jsonify({"password": password})

    # 把密码生成逻辑定义为独立类方法，修正缩进
    def generate_pwd(self, a, b, c):
        password_list=[]
        for char in range(a):
            password_list.append(random.choice(self.letters))
        for char in range(b):
            password_list.append(random.choice(self.symbols))
        for char in range(c):
            password_list.append(random.choice(self.numbers))
        random.shuffle(password_list)
        password="".join(password_list)
        return password

    def run(self):
        # 监听地址、端口和客户端保持一致
        self.app.run(host='127.0.0.1', port=1337, debug=True)

# 修正传参顺序，保证字母、符号、数字和初始化参数一一对应
mp=game(
    ["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"],
    ["!","#","$","%","&","(",")","*","+"],
    ["0","1","2","3","4","5","6","7","8","9"]
)
mp.run()

2. 修正后的客户端代码 #

import requests
import json
session=requests.session()
header={"content-type": "application/json"}

print("Welcome to the PyPassword generator!")
while True:
    # 输入时直接转整数，避免服务端类型转换报错
    letters = int(input("how many letters would you like in your password? > "))
    symbols = int(input("how many symbols would you like? > "))
    numbers = int(input("how many numbers would you like? > "))
    data={"letters":letters,"symbols":symbols,"numbers":numbers}
    print(data)
    r=session.post("http://127.0.0.1:1337/api/PyPassword_generator", data=json.dumps(data), headers=header)
    # 只有状态码为200时才解析JSON，否则打印错误信息
    if r.status_code == 200:
        json_data=r.json()
        print(f"your password is : {json_data['password']}")
        break
    else:
        print(f"request failed, status code: {r.status_code}, err: {r.text}")

修复完成后先启动服务端，再运行客户端，输入需要的字符长度即可正常生成随机密码，不会再出现405报错和JSON解析错误。

内容的提问来源于stack exchange，提问作者Corvus123