从零开始学习Node.js系列教程三：图片上传和显示
编程学习 2021-07-04 18:32www.dzhlxh.cn编程入门
这篇文章主要介绍了Node.js图片上传和显示方法,结合实例形式分析了nodejs基于http传输图片文件及显示图片的相关实现步骤与操作技巧,需要的朋友可以参考下
本文实例讲述了Node.js图片上传和显示方法。分享给大家供大家参考，具体如下：
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.');
希望本文所述对大家nodejs程序设计有所帮助。
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