Node.js中的同步 HTTP 请求

Question

我有三个组件A、B和C。 当A向B发送HTTP请求时，B向C发送另一个HTTP请求，检索相关内容并将其作为HTTP响应发送回A。

B组件由以下 Node.js 代码段表示。

var requestify = require('requestify');
// sends an HTTP request to C and retrieves the response content
function remoterequest(url, data) {
var returnedvalue;
requestify.post(url, data).then(function(response) {
var body = response.getBody();
// TODO use body to send back to the client the number of expected outputs, by setting the returnedvalue variable
});
return returnedvalue;
}
// manages A's request
function manageanotherhttprequest() {
// [...]
var res = remoterequest(url, data);
// possible elaboration of res
return res;
}

我需要返回body内容作为remoterequest函数的结果。 我注意到，目前，POST 请求是异步的。因此，在将returnedvalue变量返回到调用方法之前，永远不会分配该变量。

如何执行同步 HTTP 请求？

Answer 1

您正在使用restify，一旦调用其方法(post，get.，它将返回promise。等(。但是您创建的方法remoterequest不会返回promise供您使用.then等待。您可以使用async-await或内置promise返回promise，如下所示：

• 使用承诺：

  var requestify = require('requestify');
  // sends an HTTP request to C and retrieves the response content
  function remoterequest(url, data) {
  var returnedvalue;
  return new Promise((resolve) => {
  requestify.post(url, data).then(function (response) {
  var body = response.getBody();
  // TODO use body to send back to the client the number of expected outputs, by setting the returnedvalue variable
  });
  // return at the end of processing
  resolve(returnedvalue);
  }).catch(err => {
  console.log(err);
  });
  }
  // manages A's request
  function manageanotherhttprequest() {
  remoterequest(url, data).then(res => {
  return res;
  });
  }
  

• 使用 async-await

  var requestify = require('requestify');
  // sends an HTTP request to C and retrieves the response content
  async function remoterequest(url, data) {
  try {
  var returnedvalue;
  var response = await requestify.post(url, data);
  var body = response.getBody();
  // TODO use body to send back to the client the number of expected outputs, by setting the returnedvalue variable
  // return at the end of processing
  return returnedvalue;
  } catch (err) {
  console.log(err);
  };
  }
  // manages A's request
  async function manageanotherhttprequest() {
  var res = await remoterequest(url, data);
  return res;
  }