Javascript SwaggerTools总是使Express获取未定义的JSON对象

以代码为例：

const express = require('express');
const app = express();

SwaggerExpress.create(swaggerConfig, (err, swaggerExpress) => {
const swaggerObjectLoaded = swaggerExpress.runner.swagger;
swaggerTools.initializeMiddleware(swaggerObjectLoaded, function(middleware) {

      // Validate Swagger requests
      app.use(middleware.swaggerValidator());

      // Serve the Swagger documents and Swagger UI
      app.use(middleware.swaggerUi());

      app.use(httpContext.middleware);
      
      app.use(express.json({ limit: 4mb })); // needs to be here so I'll be able to forward all exceptions with Next() and return JSON and not HTML
      
    ....
    ....
    ....
    ....
      
}}

每当我发出POST请求并且请求到达上述代码段时，请求的主体总是未定义的

如果我把

app.use（express.json（{limit:4mb}））放在在
swaggerTools之外。初始化eMddleware
然后代码正常工作，但是我必须在内部使用它以限制错误处理

为什么身体总是没有定义？我们如何解决这个问题