nodejs入门基础实例

一个完整的基于node.js的web应用

用例：

用户可以通过浏览器使用我们的应用。
当用户请求http://domain/start时，可以看到一个欢迎页面，页面上有一个文件上传的表单。
用户可以选择一个图片并提交表单，随后文件将被上传到http://domain/upload，该页面完成上传后会把图片显示在页面上。

为实现上述功能创建4个js文件：index.js、server.js、router.js、requestHandlers.js

index.js:模拟实际项目创建的主文件，用来调用应用的其他模块，node执行这个js就能启动应用

server.js:基础的http服务器代码，创建了http服务器;基于事件驱动的事件回调；处理客户端请求，将request和response作为参数传给route（使用依赖注入的方式较松散地添加路由模块）。

router.js:使用url和querystring模块处理请求的路由。

requestHandlers.js:行为驱动执行，针对不同的url处理具体的业务逻辑

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["/show1"] = requestHandlers.show1;

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(8888);
    console.log("Server has started.");
}

exports.start = start;

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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;

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='tmp';//文件上传 临时文件存放路径
    console.log("about to parse");
    form.parse(request, function(error, fields, files) {
        console.log("parsing done");
        fs.renameSync(files.upload.path, "./tmp/text.png");
        response.writeHead(200, {"Content-Type": "text/html"});
        response.write("received image:<br/>");
        response.write("<img src='/show1' />");
        response.end();
    });
}

function show1(response) {
    console.log("Request handler 'show' was called.");
    fs.readFile("./tmp/text.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.show1 = show1;

PS:处理程序中包括非阻塞操作就会出问题。Node.js可以在不新增额外线程的情况下，依然可以对任务进行并行处理——Node.js是单线程的，它通过事件轮询（event loop）来实现并行操作，对此，我们应该要充分利用这一点，尽可能的避免阻塞操作，取而代之，多使用非阻塞操作。

nodejs入门基础实例

index.js

server.js

router.js

requestHandlers.js

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