从零开始学习Node.js例子三 图片上传和显示

浏览数：20 / 时间：2015年06月09日

index.js

var server = require("./server");
var router = require("./router");
var requestHandlers = require("./requestHandlers");

var handle = {}
handle["/"] = requestHandlers.start;
handle["/start"] = requestHandlers.start;
handle["/upload"] = requestHandlers.upload;
handle["/show"] = requestHandlers.show;

server.start(router.route, handle);

server.js

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, request);
  }

  http.createServer(onRequest).listen(3000);
  console.log("Server has started.");
}

exports.start = start;

requestHandlers.js

var querystring = require("querystring"),
    fs = require("fs"),
    formidable = require("formidable");

function start(response) {
    console.log("Request handler ‘start‘ was called.");

    var body = ‘<html>‘+
        ‘<head>‘+
        ‘<meta http-equiv="Content-Type" content="text/html; ‘+
        ‘charset=UTF-8" />‘+
        ‘</head>‘+
        ‘<body>‘+
        ‘<form action="/upload" enctype="multipart/form-data" ‘+
        ‘method="post">‘+
        ‘<input type="file" name="upload" multiple="multiple">‘+
        ‘<input type="submit" value="Upload file" />‘+
        ‘</form>‘+
        ‘</body>‘+
        ‘</html>‘;

    response.writeHead(200, {"Content-Type": "text/html"});
    response.write(body);
    response.end();
}

function upload(response, request) {
    console.log("Request handler ‘upload‘ was called.");

    var form = new formidable.IncomingForm();
    form.uploadDir = "D:\\min\\nodejsExample2\\tmp";
    console.log("about to parse1");
    form.parse(request, function(error, fields, files) {
        console.log("parsing done");
        console.log(files.upload.path);
        fs.renameSync(files.upload.path, "D:\\min\\nodejsExample2\\tmp\\test.png");
        response.writeHead(200, {"Content-Type": "text/html"});
        response.write("received image:<br/>");
        response.write("<img src=‘/show‘ />");
        response.end();
  });
}

function show(response) {
    console.log("Request handler ‘show‘ was called.");
    fs.readFile("D:\\min\\nodejsExample2\\tmp\\test.png", "binary", function(error, file) {
        if(error) {
            response.writeHead(500, {"Content-Type": "text/plain"});
            response.write(error + "\n");
            response.end();
        } else {
            response.writeHead(200, {"Content-Type": "image/png"});
            response.write(file, "binary");
            response.end();
        }
    });
}

exports.start = start;
exports.upload = upload;
exports.show = show;

router.js

function route(handle, pathname, response, request) {
    console.log("About to route a request for " + pathname);
    if (typeof handle[pathname] === ‘function‘) {
        handle[pathname](response, request);
    } else {
        console.log("No request handler found for " + pathname);
        response.writeHead(404, {"Content-Type": "text/html"});
        response.write("404 Not found");
        response.end();
    }
}

exports.route = route;

 

result:

 

 

知识点：

其中用到了fs模块的readFile读取文件，它有同步和异步两个版本。node.js中，并不是所有的API都提供了异步和同步版本，node.js不鼓励使用同步I/O。

//this is async 异步
/*
 fs.readFile调用时所做的工作只是将异步式I/O请求发送给了操作系统，然后立即返回并执行后面的语句，执行完以后进入事件循环监听事件。
 当fs接收到I/O请求完成的事件时，事件循环会主动调用回调函数以完成后续工作。
 */
var fs = require(‘fs‘);
fs.readFile(‘file.txt‘, ‘utf-8‘, function(err, data){
    if (err){
        console.error(err);
    } else {
        console.log(data);
    }
});

 

//this is sync 同步
var fs = require(‘fs‘);
var data = fs.readFileSync(‘file.txt‘, ‘utf-8‘);
console.log(data);
console.log(‘end.‘);

 

 

 

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