在 Java Azure 函数中将 Content-Type 设置为 application/json

问：

我开发了一个由 HTTP 请求触发的 Java Azure 函数，该函数对 CosmosDB 执行查询，并将检索到的数据返回给调用方（前端）。问题在于 Azure 函数的 Content-Type 是纯文本，而不是 application/json。

这是我的 Azure 函数的代码：

@FunctionName("backorders")
    public HttpResponseMessage run(
            @HttpTrigger(
                name = "req",
                methods = {HttpMethod.GET},
                authLevel = AuthorizationLevel.ANONYMOUS)
                HttpRequestMessage<Optional<String>> request,
            final ExecutionContext context) {
        context.getLogger().info("Java HTTP trigger processed a request.");
        try{     
            createConnection();
        } catch (Exception e){
            System.out.println("An error occured when connecting to the DB");
            return request.createResponseBuilder(HttpStatus.INTERNAL_SERVER_ERROR).body("An error occured when connecting to the DB").build();
        }
        ArrayList<String> supplyPlannerIds = new ArrayList<>();
        try{
            Map<String,String> headers = request.getQueryParameters();
            System.out.println(headers.values());
            String param = headers.getOrDefault("spids", "");
            if(param.equals("")){
                System.out.println("The list of Supply Planner IDs can not be empty");
                return request.createResponseBuilder(HttpStatus.BAD_REQUEST).body("The list of Supply Planner IDs can not be empty").build();
            } else {
                System.out.println("Parsing the request body");
                supplyPlannerIds = new ArrayList<String>(Arrays.asList(param.split(",")));
            }
        } catch (Exception e){
            System.out.println("An error occured when fetching the SupplyPlannerIds");
            return request.createResponseBuilder(HttpStatus.INTERNAL_SERVER_ERROR).body("An error occured when retrieving the list of SupplyPlannerIds from the request").build();
        }
        BackorderListRepo orderRepo = new BackorderListRepo(container, supplyPlannerIds);
        ArrayList<Backorder> orders = orderRepo.retrieveBackorders();
        //String json = new Gson().toJson(orders);
        return request.createResponseBuilder(HttpStatus.OK).body(orders).build();   
    }

这是我local.settings.json：

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "",
    "FUNCTIONS_WORKER_RUNTIME": "java"
  }
}

这是我host.json

{
  "version": "2.0",
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[3.*, 4.0.0)"
  } 
}

特别是当我使用 Postman 调用它时，这就是我得到的 postman 调用

我尝试了以下代码行，但没有用String json = new Gson().toJson(orders);

我也尝试了以下方法，但没有用request.getHeaders().put("content-type", "application/json");

提前非常感谢您的帮助:)