SMTP
501 Syntax Error in Parameters レスポンスのモック
The command was recognized but the parameters or arguments are syntactically invalid. The server understood what you wanted to do but could not parse the details.
完全なリファレンスを見る →1 HTTP レスポンス
HTTP/1.1 501 Syntax Error in Parameters
Content-Type: application/json
Date: Tue, 25 Feb 2026 12:00:00 GMT
Content-Length: 66
{
"error": "server_error",
"message": "Syntax Error in Parameters"
}
2 curl でテストする
curl -i https://httpbin.org/status/501
3 フレームワークで 501 Syntax Error in Parameters を返す
django
from django.http import JsonResponse
def my_view(request):
return JsonResponse(
{"error": "server_error", "message": "Syntax Error in Parameters"},
status=501,
)
flask
from flask import Flask, jsonify
app = Flask(__name__)
@app.route("/endpoint")
def my_endpoint():
return jsonify({"error": "server_error", "message": "Syntax Error in Parameters"}), 501
fastapi
from fastapi import FastAPI
from fastapi.responses import JSONResponse
app = FastAPI()
@app.get("/endpoint")
def my_endpoint():
return JSONResponse(
content={"error": "server_error", "message": "Syntax Error in Parameters"},
status_code=501,
)
express.js
// Express.js
app.get('/endpoint', (req, res) => {
res.status(501).json({"error": "server_error", "message": "Syntax Error in Parameters"});
});
spring boot
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import java.util.Map;
@RestController
public class MyController {
@GetMapping("/endpoint")
public ResponseEntity<Map<String, Object>> myEndpoint() {
return ResponseEntity
.status(501)
.body(Map.of("error", "syntax_error_in_parameters",
"message", "Syntax Error in Parameters"));
}
}
go net/http
package main
import (
"encoding/json"
"net/http"
)
func myHandler(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(501)
json.NewEncoder(w).Encode(map[string]string{
"error": "syntax_error_in_parameters",
"message": "Syntax Error in Parameters",
})
}
ruby on rails
class MyController < ApplicationController
def my_action
render json: {"error": "server_error", "message": "Syntax Error in Parameters"},
status: :syntax_error_in_parameters
end
end
asp.net core
// ASP.NET Core Minimal API
app.MapGet("/endpoint", () =>
Results.Json(
new { error = "syntax_error_in_parameters", message = "Syntax Error in Parameters" },
statusCode: 501
)
);