在HTTP请求中发送JSON字符串时，req.body在express中为空

如何解决在HTTP请求中发送JSON字符串时，req.body在express中为空

Express收到一个空的json字符串{}，但我一直无法弄清原因。我已经为json解析器尝试了bodyParser和express.json，并且得到了相同的结果。我也找不到标题有问题。下面是相关代码：

HTTP客户端对请求进行认证

    private sendRequest<T>(verb: string,url: string,body?: any)
    : Observable<T> {

    let myHeaders = new HttpHeaders();
   // myHeaders = myHeaders.set("Access-Key","<secret>");
    // myHeaders = myHeaders.set("Application-Names",["Rapid Recipes","MSsanto"]);
    

    
    return this.http.request<T>(verb,url,{
      body: JSON.stringify(body),headers: myHeaders })
      .pipe(catchError((error: Response) => throwError(`Network Error: ${error.statusText} (${error.status})`)));

  }

Express App

   var app = express();
//app.use(bodyParser());
//app.use(bodyParser.json({ limit: 'Smb' }));
//app.use(bodyParser.urlencoded({ extended: true }));
app.use(express.json());

 app.use(function (req,res,next) {
  res.setHeader('Access-Control-Allow-Origin','http://localhost:4200');
  res.setHeader('Access-Control-Allow-Methods','GET','POST','OPTIONS','PUT','PATCH','DELETE',);
  res.setHeader('Access-Control-Allow-Headers','Authorization','X-Requested-With,Content-Type','application/x-www-form-urlencoded','application/json');
  res.setHeader('Access-Control-Allow-Credentials',true);
  next();

 
app.post("/:type",function (req,res) {
  console.log('The POST was received');
  
  var typeName = req.originalUrl.substring(1).toLowerCase();
  var params = {};
  params[typeName] = 1;
  params["_id"] = 1


 console.log("the request bod is " + JSON.stringify(req.body)); //this returns {}
  

  var dbm = dbModel.findOne({},params);

 
  dbm.updateOne({ $push: { "recipe": req.body } },function (err,data)

  {

    if (err) {
      res.send(err);

    }

    else {
      res.send(data)
      console.log('data saved!');

    } } ) }
  )
});

解决方法

您没有在请求标头中发送内容类型。

myHeaders = myHeaders.set("Content-Type","application/json");