nodejs入門基礎例項
阿新 • • 發佈:2018-11-26
一個完整的基於node.js的web應用
用例:
- 使用者可以通過瀏覽器使用我們的應用。
- 當用戶請求http://domain/start時,可以看到一個歡迎頁面,頁面上有一個檔案上傳的表單。
- 使用者可以選擇一個圖片並提交表單,隨後檔案將被上傳到http://domain/upload,該頁面完成上傳後會把圖片顯示在頁面上。
為實現上述功能建立4個js檔案:index.js、server.js、router.js、requestHandlers.js
index.js:模擬實際專案建立的主檔案,用來呼叫應用的其他模組,node執行這個js就能啟動應用
server.js:基礎的http伺服器程式碼,建立了http伺服器;基於事件驅動的事件回撥;處理客戶端請求,將request和response作為引數傳給route(使用依賴注入的方式較鬆散地新增路由模組)。
router.js:使用url和querystring模組處理請求的路由。
requestHandlers.js:行為驅動執行,針對不同的url處理具體的業務邏輯
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;
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';//檔案上傳 臨時檔案存放路徑
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:處理程式中包括非阻塞操作就會出問題。Node.js可以在不新增額外執行緒的情況下,依然可以對任務進行並行處理——Node.js是單執行緒的,它通過事件輪詢(event loop)來實現並行操作,對此,我們應該要充分利用這一點,儘可能的避免阻塞操作,取而代之,多使用非阻塞操作。