我目前正在开发一个项目来开发一个API管理器来控制现有的API。
它包含＆＃34;之前＆＃34;的列表＆＃34;＆＃34;＆＃34;＆＃34;中间件，用于执行安全检查和日志记录等操作。并且＆＃34;服务＆＃34;中间件对现有API做http请求。但问题是我想让正在执行的中间件的命令是动态的，这意味着我可以加载一些配置文件来改变每次请求进入时中间件执行的顺序。
这是我之前的代码：
'use strict';
// Loading the express library
var express = require('express');
var app = express();
var service = require('./routes/index');
// Testing configurable middleware
var confirguration = {
before1: {
priority: 100,
enable: true
},
before2: {
priority: 80,
enable: true
},
service: {
priority: 50,
enable: true
},
after1: {
priority: 30,
enable: true
},
after2: {
priority: 10,
enable: true
}
}
var before1 = require('./example_middleware/before1');
var before2 = require('./example_middleware/before2');
var after1 = require('./example_middleware/after1');
var after2 = require('./example_middleware/after2');
// Fake request to simulate the /service
var fakeRequest = require('./example_middleware/fake_request');
// Function to sort the order of the middleware to be executed
var sortConfig = function(confirguration){
var sortable = [];
for (var middleware in confirguration)
// To make middlewares configurable
if (confirguration[middleware]['enable'] == true){
sortable.push([middleware, confirguration[middleware]['priority']]);
}
sortable.sort(function(a, b) {return b[1] - a[1]});
return sortable;
}
// var sortedConfig = [];
var middlewareSet = new Array();
app.use('/test', function(request, response, next){
var middleware;
var sortedConfig = sortConfig(confirguration);
for (var i in sortedConfig){
switch(sortedConfig[i][0]){
case 'before1':
middleware = before1;
break;
case 'before2':
middleware = before2;
break;
case 'service':
middleware = fakeRequest;
break;
case 'after1':
middleware = after1;
break;
case 'after2':
middleware = after2;
break;
}
// console.log(sortedConfig[i][0]);
// Execute the middleware in expected order
middlewareSet.push(middleware);
}
// request.sortedConfig = sortedConfig;
console.log(middlewareSet);
console.log('middleware list sorted');
next();
});
app.use('/test', middlewareSet);
但是我不断收到来自最后一行app.use（）的相同错误消息：
app.use（）需要中间件功能
如果我使用它可以工作：
app.use('/test', [before1, before2, fakeRequest, after1, after2]);
但它不是动态的，我误解了什么？必须有一种方法可以在express.js中执行此操作。
提前致谢。
修改 我根据Ryan的回答修改了我的代码，这里是代码：
var async = require('async');
app.use('/test', configurableMiddleWare);
function configurableMiddleWare(req, res, next) {
var operations = [];
var middleware;
var sortedConfig = sortConfig(confirguration);
// push each middleware you want to run
sortedConfig.forEach(function(fn) {
switch(fn[0]){
case 'before1':
middleware = before1;
break;
case 'before2':
middleware = before2;
break;
case 'service':
middleware = fakeRequest;
break;
case 'after1':
middleware = after1;
break;
case 'after2':
middleware = after2;
break;
}
operations.push(middleware); // could use fn.bind(null, req, res) to pass in vars
});
console.log('middleware list sorted');
// now actually invoke the middleware in series
async.series(operations, function(err) {
if(err) {
// one of the functions passed back an error so handle it here
return next(err);
}
// no errors so pass control back to express
next();
});
}
为了确保我的测试中间件没有出现任何错误，以下是其中一个的例子：
'use strict';
var express = require('express');
var router = express.Router();
router.route('/')
.all(function(request, response, next){
console.log('This is middleware BEFORE1');
next();
});
module.exports = router;
现在，当我运行我的应用程序时，我从npm得到以下错误：
TypeError：无法调用方法＆＃39; indexOf＆＃39;未定义的
在Function.proto.handle（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/express/lib/router/index.js:130:28） 在路由器（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/express/lib/router/index.js:35:12） at /Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:610:21 at /Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:249:17 在iterate（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:149:13） at async.eachSeries（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:165:9） 在_asyncMap（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:248:13） at Object.mapSeries（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:231:23） at Object.async.series（/Users/jialunliu/Documents/SOA_project/FAT-LADY/node_modules/async/lib/async.js:608:19） 在configurableMiddleWare（/Users/jialunliu/Documents/SOA_project/FAT-LADY/app.js:135:11）
哪一行来自该行
async.series(operations, function(err){})
我一直收到这种错误信息，说这个函数无法读取这个函数数组＆＃34;操作＆＃34; ....
答案 0 :(得分：8)
我认为你走在正确的轨道上，你只需要调整一些东西。我会用app.use()注册一个顶级函数，然后在该函数中执行所有动态内容。更新我对一个工作示例的回答。请务必先安装异步npm install --save async
// define all middleware functions
var middleware = {
mw1: function(req, res, next) {
console.log('mw 1');
next();
},
mw2: function(req, res, next) {
console.log('mw 2');
next();
},
mw3: function(req, res, next) {
console.log('mw 3');
next();
},
mw4: function(req, res, next) {
console.log('mw 4');
next();
}
};
// register our "top level function"
app.use(configurableMiddleware);
var requestCount = 1; // this is just for the working example
function configurableMiddleware(req, res, next) {
var isEvenRequest = requestCount++ % 2 === 0; // simple logic to alternate which "configurable" middleware to use
var operations; // in the real world you could build this array dynamically, for now we just hardcode two scenarios as an example
// Each request to http://localhost:3000 will alternate which middleware is used, so you will see a different log each time
if(isEvenRequest) {
console.log('Even request should log mw2 and mw4');
// .bind(null, req, res) makes sure that the middleware gets the request and response objects when they are invoked,
// as of this point they still haven't been invoked...
operations = [middleware.mw2.bind(null, req, res), middleware.mw4.bind(null, req, res)];
}
else {
console.log('Odd request should log mw1 and mw3');
operations = [middleware.mw1.bind(null, req, res), middleware.mw3.bind(null, req, res)];
}
// invoke each middleware in series - you could also do async.parallel if the order of middleware doesn't matter
// using the async module: https://github.com/caolan/async
async.series(operations, function(err) {
if(err) {
console.log('There was a problem running the middleware!');
return next(err);
}
// all middleware has been run
next();
});
}
有关.bind（）的更多信息，请参阅https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind
答案 1 :(得分：2)
connect-sequence：用于特定目的的专用节点模块：您可以使用专为此目的设计的模块connect-sequence：
npm install --save connect-sequence
请参阅：
然后，这里是一个用法示例：
/**
* Product API
* @module
*/
var ConnectSequence = require('connect-sequence')
var productsController = require('./products.controller')
module.exports = productRouter
function productRouter (app) {
app.route('/api/products/:productId')
.get(function (req, res, next) {
// Create a ConnectSequence instance and setup it with the current `req`,
// `res` objects and the `next` callback
var seq = new ConnectSequence(req, res, next)
// build the desired middlewares sequence thanks to:
// - ConnectSequence#append(mid0, ..., mid1),
// - ConnectSequence#appendList([mid0, ..., mid1])
// - and ConnectSequence#appendIf(condition, mid)
if (req.query.filter) {
seq.append(productsController.filter)
}
if (req.query.format) {
seq.append(
productsController.validateFormat,
productsController.beforeFormat,
productsController.format,
productsController.afterFormat
)
}
// append the productsController.prepareResponse middleware to the sequence
// only if the condition `req.query.format && req.formatedProduct` is true
// at the moment where the middleware would be called.
// So the condition is tested after the previous middleware is called and thus
// if the previous modifies the `req` object, we can test it.
seq.appendIf(isProductFormatted, productsController.prepareResponse)
seq.append(productsController.sendResponse)
// run the sequence
seq.run()
})
app.param('productId', function (req, res, next, id) {
// ... yield the product by ID and bind it to the req object
})
function isProductFormatted (req) {
return Boolean(req.formatedProduct)
}
}
如果您喜欢并使用connect-sequence，但如果您发现错误或需要一些新功能，请随时发布问题或提交拉取请求！
答案 2 :(得分：1)
根据@Ryan代码背后的想法，我提出了这个功能。它执行一个中间件列表，以便根据需要绑定变量，允许所有内容仅由executeMiddlewareList([middleware1, middleware2...], req, res, next);执行。对于每个中间件req, res都会传递，并且来自async.eachSeries的回调。这意味着在中间件内调用next()时，将从列表中处理下一个。如果中间件抛出next(err)错误，执行将停止，您可以手动处理。
function executeMiddlewareList (middlewareList, req, res, next) {
async.eachSeries(middlewareList, function(middleware,callback) {
middleware.bind(null,req,res,callback)()
}, function(err) {
if (err) return res.status(500).json({error: err});
next();
})
}
function testMid (number) {
return function (req, res, next) {
log.debug('req.test from', req.test, " to ", number);
req.test=number;
next();
}
}
router.get('/test', function(req, res, next) {
m.executeMiddlewareList([test(1), test(2)], req, res, next);
//Output: req.test from undefined to 1
// req.test from 1 to 2
}, function (req,res) {
//Do stuff after the executeMiddlewareList, req.test = 2
})
答案 3 :(得分：0)
最后，根据Ryan的说法找到答案，代码看起来像这样：
function configurableMiddleWare(req, res, next) {
var operations = [];
var middleware;
var sortedConfig = sortConfig(confirguration);
// push each middleware you want to run
sortedConfig.forEach(function(fn) {
switch(fn[0]){
case 'before1':
middleware = before1;
break;
case 'before2':
middleware = before2;
break;
case 'service':
middleware = fakeRequest;
break;
case 'after1':
middleware = after1;
break;
case 'after2':
middleware = after2;
break;
}
console.log(fn[0]);
console.log(middleware);
operations.push(middleware.bind(null, req, res)); // could use fn.bind(null, req, res) to pass in vars
});
console.log('middleware list sorted');
// now actually invoke the middleware in series
async.series(operations, function(err) {
if(err) {
// one of the functions passed back an error so handle it here
return next(err);
}
console.log('middleware get executed');
// no errors so pass control back to express
next();
});
}
app.use('/test', configurableMiddleWare);
关键步骤确实是operations.push(middleware.bind(null, req, res));
说实话，我不明白究竟是什么意思。我知道这是将“req”和“res”变量传递给中间件，但我没有得到前面“null”的意思。非常感谢，如果有人可以帮我澄清这一点。