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轻松创建nodejs服务器(9):实现非阻塞操作

时间:2024-3-2 11:04     作者:韩俊     分类: Javascript


我们要将response对象(从服务器的回调函数onRequest()获取)通过请求路由传递给请求处理程序。随后,处理程序就可以采用该对象上的函数来对请求作出响应。

我们先对server.js做出修改:

var http = require("http");

var url = require("url");

function start(route, handle) {

  function onRequest(request, response) {

 var pathname = url.parse(request.url).pathname;

 console.log("Request for " + pathname + " received."); 

 route(handle, pathname, response); 

  }

  http.createServer(onRequest).listen(8888);

  console.log("Server has started.");

}

exports.start = start;

我们将response对象作为第三个参数传递给route()函数,并且,我们将onRequest()处理程序中所有有关response的函数调都移除,因为我们希望这部分工作让route()函数来完成。

接下来修改 router.js:

function route(handle, pathname, response) {

  console.log("About to route a request for " + pathname);

  if (typeof handle[pathname] === 'function') {

 handle[pathname](response);

  } else {

 console.log("No request handler found for " + pathname);

 response.writeHead(404, {"Content-Type": "text/plain"});

 response.write("404 Not found");

 response.end();

  }

}

exports.route = route;

同样的模式:相对此前从请求处理程序中获取返回值,这次取而代之的是直接传递response对象。 如果没有对应的请求处理器处理,我们就直接返回“404”错误。

接下来修改requestHandler.js:

var exec = require("child_process").exec;

function start(response) {

  console.log("Request handler 'start' was called.");

  exec("ls -lah", function (error, stdout, stderr) {

 response.writeHead(200, {"Content-Type": "text/plain"});

 response.write(stdout);

 response.end();

  });

}

function upload(response) {

  console.log("Request handler 'upload' was called.");

  response.writeHead(200, {"Content-Type": "text/plain"});

  response.write("Hello Upload");

  response.end();

}

exports.start = start;

exports.upload = upload;

我们的处理程序函数需要接收response参数,为了对请求作出直接的响应。 start处理程序在exec()的匿名回调函数中做请求响应的操作,而upload处理程序仍然是简单的回复“Hello World”,只是这次是使用response对象而已。

如果想要证明/start处理程序中耗时的操作不会阻塞对/upload请求作出立即响应的话,可以将requestHandlers.js修改为如下形式:

var exec = require("child_process").exec;

function start(response) {

  console.log("Request handler 'start' was called.");

  exec("find /",

      { timeout: 10000, maxBuffer: 20000*1024 },

      function (error, stdout, stderr) {

  response.writeHead(200, {"Content-Type": "text/plain"});

  response.write(stdout);

  response.end();

      }

  );

}

function upload(response) {

  console.log("Request handler 'upload' was called.");

  response.writeHead(200, {"Content-Type": "text/plain"});

  response.write("Hello Upload");

  response.end();

}

exports.start = start;

exports.upload = upload;

这样一来,当请求http://localhost:8888/start的时候,会花10秒钟的时间才载入,而当请求http://localhost:8888/upload的时候,会立即响应,纵然这个时候/start响应还在处理中。

标签: javascript

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