我们需要编写一个节点应用程序，它可以从数据库中读取图像的URL（大约超过百万）。使用图像大小的npm包来检索高度，宽度等图像元数据。这里应该是一个可以列出结果的API。
我能够控制日志数据但是当我将其转换为API时，我需要将数据块化，以便它可以开始出现在浏览器上，我无法做到这一点并需要帮助。这是我的代码
var express = require('express');
var url = require('url');
var http = require('http');
var sizeOf = require('image-size');
const sql = require('mssql');
var app = express();
var port = process.env.PORT || 3000;
const hostname = 'localhost';
var config1 = {
user: '*********',
password: '*********',
server: '*********',
database: '*******',
port: 1433,
debug: true,
options: {
encrypt: false // Use this if you're on Windows Azure
}
};
app.get('/', function(req, res){
//res.writeHead(200, { 'Content-Type': 'application/json' });
var finalResult = [];
sql.close();
sql.connect(config1, function (err) {
if (err) console.log(err);
const request = new sql.Request()
var myQuery = `select imagename from media`;
request.stream = true;
request.query(myQuery);
request.on('row', row => {
//console.log('Image : ' + row.ImageUrl);
if (row.ImageUrl != ''){
if (row.ImageUrl.indexOf('http') < 0)
row.ImageUrl = "http:" + row.ImageUrl;
var options = url.parse(row.ImageUrl);
http.get(options, function (response) {
if (response.statusCode == 200)
{
var chunks = [];
response.on('data', function (chunk) {
chunks.push(chunk);
}).on('end', function() {
var buffer = Buffer.concat(chunks);
//console.log(options.href);
//console.log(sizeOf(buffer).height);
var result = {};
result.MaskUrl = row.MaskUrl;
result.ImageUrl = options.href;
result.Height = sizeOf(buffer).height;
result.Width = sizeOf(buffer).width;
result.statusCode = 200;
finalResult.push(result);
//console.log(result);
console.log(finalResult);
res.write(result, function(){
res.end();
});
});
}
else
{
var result = {};
result.MaskUrl = row.MaskUrl;
result.ImageUrl = options.href;
result.Height = 0;
result.Width = 0;
result.statusCode = response.statusCode;
finalResult.push(result);
console.log(result);
res.write(result, function(){
res.end();
});
}
});
}
})
request.on('error', err => {
console.log ('Error for ' + row.ImageUrl );
})
request.on('done', err => {
console.log('Last Time' + finalResult.length);
})
// request.query(myQuery,(err,result) =>{
// console.log(result);
// });
});
console.log('Last Time' + finalResult.length);
res.send(finalResult);
});
app.listen(port, hostname, function(){
console.log('ImageSize running on PORT: ' + port);
});
我尝试了res.write，res.end没有任何成功。
答案 0 :(得分：0)
问题的可能原因在于：
res.write(result, function(){
res.end();
});
您在读取第一张图片后结束并关闭请求。
我会稍微重写一下代码并使用一些功能框架，比如scramjet，直接从数据库中传输数据。正如尼古拉斯指出的那样，运行你的代码并不容易，所以我盲目地写作 - 但是如果你修复了我明显的任何错误，那么这应该是正常的：
首先：
npm install scramjet JSONStream node-fetch
接下来，试试这段代码：
var express = require('express');
var sizeOf = require('image-size');
const sql = require('mssql');
var app = express();
var port = process.env.PORT || 3000;
const hostname = 'localhost';
const {DataStream} = require('scramjet');
const fetch = require('node-fetch');
const JSONStream = require('JSONStream');
var config1 = {
user: '*********',
password: '*********',
server: '*********',
database: '*******',
port: 1433,
debug: true,
options: {
encrypt: false // Use this if you're on Windows Azure
}
};
app.get('/', function(req, res, next){
// you should consider not doing these two lines on each request,
// but I don't want to mess you code...
sql.close();
sql.connect(config1, function (err) {
if (err) next(err);
res.writeHead(200, { 'Content-Type': 'application/json' });
const request = new sql.Request();
var myQuery = `select imagename from media`;
request.stream = true;
request.query(myQuery);
const stream = new DataStream();
request.on('row', row => stream.write(row));
stream.filter(
row => row.ImageUrl !== ''
)
.map(
async row => {
if (row.ImageUrl.indexOf('http') !== 0) // url must start with http.
row.ImageUrl = "http:" + row.ImageUrl;
const response = await fetch(row.ImageUrl);
let size = {width:0, height:0};
if (response.status === 200) {
const buffer = await response.buffer();
size = sizeOf(buffer);
}
return {
MaskUrl: row.MaskUrl,
ImageUrl: row.ImageUrl,
Height: size.height,
Width: size.width,
statusCode: response.status
};
}
)
.pipe(
JSONStream.stringify()
).pipe(
res
);
request.on('error', () => {
res.writeHead(500, { 'Content-Type': 'application/json' });
stream.end("{error:true}");
});
request.on('done', () => stream.end());
});
});
app.listen(port, hostname, function(){
console.log('ImageSize running on PORT: ' + port);
});