node.js - Node.js 中的同步 HTTP 请求

Question

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

该B组件由以下 Node.js 片段表示。

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;
}

body我需要作为remoterequest函数的结果返回内容。我注意到，目前，POST 请求是异步的。因此，在将returnedvalue变量返回给调用方法之前，永远不会分配变量。

如何执行同步 HTTP 请求？

Answer 1

您正在使用restifywhich 将promise在调用其方法（post，get..etc）时返回。但是您创建的方法remoterequest不会返回promise让您等待使用.then. promise您可以使用async-await或内置返回，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;
    });
  }
  

• 使用异步等待

  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;
  }