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The previous chapter says router is mainly used to describe the relationship between the request URL and the Controller that processes the request eventually, so what is a Controller used for?
Generally speaking, a Controller is used for paring users' input and send back the relative result after processing, for example
It is generally recommended that the Controller layer is responsible for processing request parameters(verification and transformation) from user requests, then calls related business methods in service, encapsulates and send back business result:
All Controller files must be put under app/controller directory. Controllers can be written in various patterns depending on various project scenarios and develop styles.
You can write a Controller by defining a Controller class:
// app/controller/post.js
const Controller = require('beidou').Controller;
class PostController extends Controller {
* create() {
const { ctx, service } = this;
const createRule = {
title: { type: 'string' },
content: { type: 'string' },
};
// verify parameters
ctx.validate(createRule);
// assemble parameters
const author = ctx.session.userId;
const req = Object.assign(ctx.request.body, { author });
// calls Service to handle business
const res = yield service.post.create(req);
// set response content and status code
ctx.body = { id: res.id };
ctx.status = 201;
}
}
module.exports = PostController;
We've defined a PostController class above and every method of this Controller can be used in Router.
// app/router.js
module.exports = {
app.post('createPost', '/api/posts', 'post.create');
}
The defined Controller class initializes a new object for every request accessing the server, and, for the example above, several attributes are attached to this since the Controller class inherits app.Controller.
this.ctx: the instance of Context for current request, through which we can access many attributes and methods, encapsulated by the framework, of current request conveniently.this.app: the instance of Application for current request, through which we can access global objects and methods provided by the framework.this.service: Service defined by the application, through which we can access the abstract business layer, equivalent to this.ctx.service.this.config: the application's run-time config.Defining a Controller class helps us not only abstract the Controller layer codes better(e.g. universal routines can be abstracted as private) but also encapsulate methods that are widely used in the application by defining a customized Controller base class.
In App Start, the application is allowed to define a customized Controller base class, and methods in base class can be used by Controllers in app/controller therefore.
// app.js
module.exports = app => {
class CustomController extends app.Controller {
get user() {
return this.ctx.session.user;
}
success(data) {
this.ctx.body = {
success: true,
data,
};
}
notFound(msg) {
msg = msg || 'not found';
this.ctx.throw(404, msg);
}
}
app.Controller = CustomController;
}
Now we can use base class' methods when defining Controllers for the application:
//app/controller/post.js
module.exports = app => {
return class PostController extends app.Controller {
* list() {
const posts = yield this.service.listByUser(this.user);
this.success(posts);
}
};
};
Every Controller is a generation function, whose this is point to the instance of the request Context through which we can access many attributes and methods, encapsulated by the framework, of current request conveniently.
For example, when we define a Controller relative to POST /api/posts, we create a post.js file under app/controller directory.
// app/controller/post.js
exports.create = function* () {
const createRule = {
title: { type: 'string' },
content: { type: 'string' },
};
// verify parameters
this.validate(createRule);
// assemble parameters
const author = this.session.userId;
const req = Object.assign(this.request.body, { author });
// calls Service to handle business
const res = yield this.service.post.create(req);
// set response content and status code
this.body = { id: res.id };
this.status = 201;
};
In the above example, we introduce some new concepts, however it's still intuitional and understandable. We'll explain these new concepts in detail soon.
Since Controller is probably the only place to interact with HTTP protocol when developing business logics, it's necessary to have a quick look at how HTTP protocol works before going on.
If we send a HTTP request to access the previous example Controller:
curl -X POST http://localhost:3000/api/posts --data '{"title":"controller", "content": "what is controller"}' --header 'Content-Type:application/json; charset=UTF-8'
The HTTP request sent by curl looks like this:
POST /api/posts HTTP/1.1
Host: localhost:3000
Content-Type: application/json; charset=UTF-8
{"title": "controller", "content": "what is controller"}
The 1st line of the request contains 3 information, first 2 of which are commonly used:
POST in this example./api/posts, the query, if any, is placed here too.From the 2nd line to the place where the 1st empty line appears is the Header part of the request and many useful attributes are here including, as you may see, Host, Content-Type and Cookie, User-Agent, etc. 2 headers in this request:
Host: when we send a request in the browser, the domain is resolved to server IP by DNS and, as well, the domain and port are send to the server in the Host header by the browser.Content-Type: when we have a body in our request, the Content-Type is provided to describe the type of our request body.The whole following content is the request body, which can be set by POST, PUT, DELETE, etc. methods and the server resolves the request body according to Content-Type.
When the sever finishes to process the request, a HTTP response is send back to the client:
HTTP/1.1 201 Created
Content-Type: application/json; charset=utf-8
Content-Length: 8
Date: Mon, 09 Jan 2017 08:40:28 GMT
Connection: keep-alive
{"id": 1}
The 1st line contains 3 segments, among which the status code is used mostly, in this case, it's 201 which means the server has created a resource successfully.
Similar to the request, the header part begins at the 2nd line and end at the place where the 1st empty line appears, in this case, they are Content-Type and Content-Length indicating the response format is JSON and the length is 8 bytes.
The remaining part is the actual content of this response.
It can be seen from the above HTTP request examples that there are many places can be used to put user request data. The framework, binding the Context instance to Controllers, provides many convenient methods and attributes to acquire parameters sent by users through HTTP request.
Usually the Query String, string following ? in the URL, is used to send parameters by request of GET type. For example, category=beidou&language=node in GET /posts?category=beidou&language=node is parameter that user sends. We can acquire this parsed parameter body through context.query:
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* listPosts() {
const query = this.ctx.query;
// {
// category: 'beidou',
// language: 'node',
// }
}
};
If duplicated keys exists in Query String, only the 1st value of this key is used by context.query and all other values it appear later will be omitted. That is to say, for request GET /posts?category=beidou&category=koa, what context.query acquires is { category: 'beidou' }.
This is for unity reason, since, by design, we usually do not let users pass parameters with same keys in Query String then we write codes like below:
const key = ctx.query.key || '';
if (key.startsWith('beidou')) {
// do something
}
Or if someone passes parameters with same keys in Query String on purpose, system error may be thrown. To avoid this, the framework guarantee the parameter be of string type whenever it is acquired from context.query.
Sometimes our system is designed to accept same keys sent by users, like GET /posts?category=beidou&id=1&id=2&id=3. For this situation, the framework provides context.queries object that parses Query String and put duplicated data into an array:
// GET /posts?category=beidou&id=1&id=2&id=3
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* listPosts() {
console.log(this.ctx.queries);
// {
// category: [ 'beidou' ],
// id: [ '1', '2', '3' ],
// }
}
};
The value type for keys in context.queries is array for sure if any.
In Router part, we say Router is allowed to declare parameters which can be acquired by context.params.
// app.get('/projects/:projectId/app/:appId', 'app.listApp');
// GET /projects/1/app/2
const Controller = require('beidou').Controller;
module.exports = class AppController extends Controller {
* listApp() {
assert.equal(this.ctx.params.projectId, '1');
assert.equal(this.ctx.params.appId, '2');
}
};
Although we can pass parameters through URL, but constraints exist:
In the above HTTP request message example, we can learn, following the header, there's a body part that can be used to put parameters for POST, PUT and DELETE, etc. The Content-Type is to be sent by clients(browser) in the same time indicating the type of request body. Two mostly used data format are JSON and Form in Web developing for transferring data.
The bodyParser middleware is built in by the framework to parse these 2 kinds of request to be an object mounting to context.request.body. Since it's not recommended by the HTTP protocol to pass a body by GET and HEAD methods, context.request.body cannot be used for GET and HEAD methods.
// POST /api/posts HTTP/1.1
// Host: localhost:3000
// Content-Type: application/json; charset=UTF-8
//
// {"title": "controller", "content": "what is controller"}
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* listPosts() {
assert.equal(this.ctx.request.body.title, 'controller');
assert.equal(this.ctx.request.body.content, 'what is controller');
}
};
The framework configures the bodyParser using default parameters and features below are available out of the box:
application/json, application/json-patch+json, application/vnd.api+json and application/csp-report, it parses the request body as JSON format and limits the maximum length of the body down to 100kb.application/x-www-form-urlencoded, it parses the request body as Form format and limits the maximum length of the body down to 100kb.The mostly adjusted config field is the maximum length of the request body for parsing which can be configured in config/config.default.js to overwrite the default value of the framework:
module.exports = {
bodyParser: {
jsonLimit: '1mb',
formLimit: '1mb',
},
};
If user request exceeds the maximum length for parsing that we configured, the framework will throw an exception whose status code is 413; if request body failed to be parsed(e.g. malformed JSON), an exception with status code 400 will be thrown.
Note: when adjusting the maximum length of the body for bodyParser, the reverse proxy, if any in front of our application, should be adjusted as well to support the newly configured length of the body.
Files, too, can be sent by the request body besides parameters, and browsers usually send file in multipart/form-data type. The uploaded files can be acquired by the framework built-in plugin Multipart.
In Controller, we can acquire the file stream of the uploaded file through interface context.getFileStream*().
<form method="POST" action="/upload?_csrf={{ ctx.csrf | safe }}" enctype="multipart/form-data">
title: <input name="title" />
file: <input name="file" type="file" />
<button type="submit">upload</button>
</form>
const path = require('path');
const sendToWormhole = require('stream-wormhole');
const Controller = require('beidou').Controller;
module.exports = class UploaderController extends Controller {
* upload() {
const ctx = this.ctx;
const stream = yield ctx.getFileStream();
const name = 'beidou-multipart-test/' + path.basename(stream.filename);
// file processing, e.g. uploading to the cloud storage etc.
let result;
try {
result = yield ctx.oss.put(name, stream);
} catch (err) {
// must consume the file stream, or the browser will get stuck
yield sendToWormhole(stream);
throw err;
}
ctx.body = {
url: result.url,
// all form fields can be acquired by `stream.fields`
fields: stream.fields,
};
}
};
To acquire user uploaded files conveniently by context.getFileStream, 2 conditions must be matched:
If more than 1 file are to be uploaded, ctx.getFileStream() is no longer the way but the following:
const sendToWormhole = require('stream-wormhole');
const Controller = require('beidou').Controller;
module.exports = class UploaderController extends Controller {
* upload() {
const ctx = this.ctx;
const parts = ctx.multipart();
let part;
// parts() return a promise
while ((part = yield parts()) != null) {
if (part.length) {
// it is field in case of arrays
console.log('field: ' + part[0]);
console.log('value: ' + part[1]);
console.log('valueTruncated: ' + part[2]);
console.log('fieldnameTruncated: ' + part[3]);
} else {
if (!part.filename) {
// it occurs when user selects no file then click to upload(part represents file, while part.filename is empty)
// more process should be taken, like giving an error message
return;
}
// part represents the file stream uploaded
console.log('field: ' + part.fieldname);
console.log('filename: ' + part.filename);
console.log('encoding: ' + part.encoding);
console.log('mime: ' + part.mime);
// file processing, e.g. uploading to the cloud storage etc.
let result;
try {
result = yield ctx.oss.put('beidou-multipart-test/' + part.filename, part);
} catch (err) {
// must consume the file stream, or the browser will get stuck
yield sendToWormhole(part);
throw err;
}
console.log(result);
}
}
console.log('and we are done parsing the form!');
}
};
To ensure the security of uploading files, the framework limits supported file formats and the whitelist supported by default is below:
// images
'.jpg', '.jpeg', // image/jpeg
'.png', // image/png, image/x-png
'.gif', // image/gif
'.bmp', // image/bmp
'.wbmp', // image/vnd.wap.wbmp
'.webp',
'.tif',
'.psd',
// text
'.svg',
'.js', '.jsx',
'.json',
'.css', '.less',
'.html', '.htm',
'.xml',
// tar
'.zip',
'.gz', '.tgz', '.gzip',
// video
'.mp3',
'.mp4',
'.avi',
New file extensions can be add by configuring the config/config.default.js file or rewriting the whole whitelist.
module.exports = {
multipart: {
fileExtensions: [ '.apk' ], // supports .apk file extention
},
};
module.exports = {
multipart: {
whitelist: [ '.png' ], // overwrite the whole whitelist, only '.png' is allowed to be uploaded
},
};
Note: when the whitelist attribute is used, the fileExtensions attribute will be discarded.
Apart from URL and request body, some parameters can be sent by request header. The framework provides some helper attributes and methods to retrieve them.
context.headers, context.header, context.request.headers, context.request.header: these methods are equivalent and all of them get the whole header object.context.get(name), context.request.get(name): get the value of one parameter from the request header, if the parameter does not exist, an empty string is returned.context.get(name) rather than context.headers['name'] because the former handles upper/lower case automatically.Since header is special, some of which are given specific meanings by the HTTP protocol (like Content-Type, Accept), some are set by the reverse proxy as a convention (X-Forwarded-For), and the framework provides some convenient getters for them as well, for more details please refer to API.
Specially when we set config.proxy = true to deploy the application behind the reverse proxy (Nginx), some Getters' internal process may be changed.
context.host
Reads the header's value configured by config.hostHeaders firstly, if fails, then it tries to get the value of host header, if fails again, it returns an empty string.
config.hostHeaders defaults to x-forwarded-host.
context.protocol
When you get protocol through this Getter, it checks whether current connection is an encrypted one or not, if it is, it returns HTTPS.
When current connection is not an encrypted one, it reads the header's value configured by config.protocolHeaders to check HTTP or HTTPS, if it fails, we can set a safe-value(defaults to HTTP) through config.protocol in the configuration.
config.protocolHeaders defaults to x-forwarded-proto.
context.ips
A IP address list of all intermediate equipments that a request go through can be get by context.ips, only when config.proxy = true, it reads the header's value configured by config.ipHeaders instead, if fails, it returns an empty array.
config.ipHeaders defaults to x-forwarded-for.
context.ip
The IP address of the sender of the request can be get by context.ip, it reads from context.ips firstly, if context.ips is empty, it returns the connection sender's IP address.
Note: ip and ips are different, if config.proxy = false, ip returns the connection sender's IP address while ips returns an empty array.
All HTTP requests are stateless but, on the contrary, our Web applications usually need to know who sends the requests. To make it through, the HTTP protocol designs a special request header: Cookie. With the response header (set-cookie), the server is able to send a few data to the client, the browser saves these data according to the protocol and brings them along with the next request(according to the protocol and for safety reasons, only when accessing websites that match the rules specified by Cookie does the browser bring related Cookies).
Through context.cookies, we can conveniently and safely set and get Cookie in Controller.
const Controller = require('beidou').Controller;
module.exports = class CookieController extends Controller {
* add() {
const ctx = this.ctx;
const count = ctx.cookies.get('count');
count = count ? Number(count) : 0;
ctx.cookies.set('count', ++count);
ctx.body = count;
}
* remove() {
const ctx = this.ctx;
const count = ctx.cookies.set('count', null);
ctx.status = 204;
}
};
Although Cookie is only a header in HTTP, multiple key-value pairs can be set in the format of foo=bar;foo1=bar1;.
In Web applications, Cookie is usually used to send the identity information of the client, so it has many safety related configurations which can not be ignored, Cookie explains the usage and safety related configurations of Cookie in detail and is worth being read in depth.
By using Cookie, we can create an individual Session specific to every user to store user identity information related data which is encrypted then stored in Cookie to perform session persistence across requests.
The framework builds in Session plugin, which provides context.session for us to get or set current user's Session.
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
*fetchPosts() {
const ctx = this.ctx;
// get data from Session
const userId = ctx.session.userId;
const posts = yield ctx.service.post.fetch(userId);
// set value to Session
ctx.session.visited = ctx.session.visited ? ctx.session.visited++ : 1;
ctx.body = {
success: true,
posts,
};
}
};
It's quite intuition to use Session, just get or set directly, and if set it to null, it is deleted.
const Controller = require('beidou').Controller;
module.exports = class SessionController extends Controller {
* deleteSession() {
this.ctx.session = null;
}
};
Like Cookie, Session has many safety related configurations and functions etc., so it's better to read Session in depth in ahead.
There mainly are these attributes below can be used to configure Session in config.default.js:
module.exports = {
key: 'EGG_SESS', // the name of key-value pairs, which is specially used by Cookie to store Session
maxAge: 86400000, // Session maximum valid time
};
After getting parameters from user requests, in most cases, it is a must to validate these parameters.
With the help of the convenient parameter validation mechanism provided by Validate plugin, with which we can do all kinds of complex parameter validations.
// config/plugin.js
exports.validate = {
enable: true,
package: 'egg-validate',
};
Validate parameters directly through context.validate(rule, [body]):
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* create() {
// validate parameters
// if the second parameter is absent, `ctx.request.body` is validated automatically
this.ctx.validate({
title: { type: 'string' },
content: { type: 'string' },
});
}
};
When the validation fails, an exception will be thrown immediately with an error code of 422 and an errors field containing the detailed information why it fails. You can capture this exception through try catch and handle it all by yourself.
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* create() {
const ctx = this.ctx;
try {
ctx.validate(createRule);
} catch (err) {
ctx.logger.warn(err.errors);
ctx.body = { success: false };
return;
}
}
};
The parameter validation is done by Parameter, and all supported validation rules can be found in its document.
In addition to built-in validation types introduced in the previous section, sometimes we hope to customize several validation rules to make the development more convenient and now customized rules can be added through app.validator.addRule(type, check).
// app.js
app.validator.addRule('json', (rule, value) => {
try {
JSON.parse(value);
} catch (err) {
return 'must be json string';
}
});
After adding the customized rule, it can be used immediately in Controller to do parameter validation.
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* handler() {
const ctx = this.ctx;
// query.test field must be a json string
const rule = { test: 'json' };
ctx.validate(rule, ctx.query);
}
};
We do not prefer to implement too many business logics in Controller, so a Service layer is provided to encapsulate business logics, which not only increases the reusability of codes but also makes it easy for us to test our business logics.
In Controller, any method of any Service can be called and, in the meanwhile, Service is lazy loaded which means it is initialized by the framework on the first time it is accessed.
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
* create() {
const ctx = this.ctx;
const author = ctx.session.userId;
const req = Object.assign(ctx.request.body, { author });
// using service to handle business logics
const res = yield ctx.service.post.create(req);
ctx.body = { id: res.id };
ctx.status = 201;
}
};
To write a Service in detail, please refer to Service.
After business logics are handled, the last thing Controller should do is to send the processing result to users with an HTTP response.
HTTP designs many Status Code, each of which indicates a specific meaning, and setting the status code correctly makes the response more semantic.
The framework provides a convenient Setter to set the status code:
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
*create() {
// set status code to 201
this.ctx.status = 201;
}
};
As to which status code should be used for a specific case, please refer to status code meanings on List of HTTP status codes
Most data is sent to receivers through the body and, just like the body in the request, the body sent by the response demands a set of corresponding Content-Type to inform clients how to parse data.
application/json, indicating it's a JSON string.text/html, indicating it's a piece of HTML code.const Controller = require('beidou').Controller;
module.exports = class ViewController extends Controller {
* show() {
this.ctx.body = {
name: 'beidou',
category: 'framework',
language: 'Node.js',
};
}
* page() {
this.ctx.body = '<html><h1>Hello</h1></html>';
}
};
Due to the Stream feature of Node.js, we need to send the response by Stream in some cases, e.g., sending a big file, the proxy server returns content from upstream straightforward, the framework, too, endorses setting the body to be a Stream directly and it handles error events on this stream well in the meanwhile.
const Controller = require('beidou').Controller;
module.exports = class ProxyController extends Controller {
* proxy() {
const ctx = this.ctx;
const result = yield ctx.curl(url, {
streaming: true,
});
ctx.set(result.header);
// result.res is stream
ctx.body = result.res;
}
};
Usually we do not write HTML pages by hand, instead we generate them by a template engine.
Beidou load beidou-view-react by default, then ctx.render(template) can be used to render templates to HTML directly.
Sometimes we need to provide API services for pages in a different domain, and, for historical reasons, CORS fails to make it through, while JSONP does.
Since misuse of JSONP leads to dozens of security issues, the framework supplies a convenient way to respond JSONP data, encapsulating JSONP XSS Related Security Precautions, supporting the validation of CSRF and referrer.
app.jsonp() provides a middleware for the controller to respond JSONP data. We may add this middleware for controllers demanding for JSONP supporting in the router:// app/router.js
module.exports = app => {
const jsonp = app.jsonp();
app.get('/api/posts/:id', jsonp, 'posts.show');
app.get('/api/posts', jsonp, 'posts.list');
};
// app/controller/posts.js
const Controller = require('beidou').Controller;
module.exports = class PostController extends Controller {
*show() {
this.ctx.body = {
name: 'beidou',
category: 'framework',
language: 'Node.js',
};
}
};
When user requests access this controller through a corresponding URL, if the query contains the _callback=fn parameter, data is returned in JSONP format, otherwise in JSON format.
By default, the framework determines whether to return data in JSONP format or not depending on the _callback parameter in the query, and the method name set by _callback must be less than 50 characters. Applications may overwrite the default configuration globally in config/config.default.js:
// config/config.default.js
exports.jsonp = {
callback: 'callback', // inspecting the `callback` parameter in the query
limit: 100, // the maximum size of the method name is 100 characters
};
With the configuration above, if a user requests /api/posts/1?callback=fn, a JSONP format response is sent, if /api/posts/1, a JSON format response is sent.
Also we can overwrite the default configuration in app.jsonp() when creating the middleware and therefore separate configurations is used for separate routers:
// app/router.js
module.exports = app => {
app.get('/api/posts/:id', app.jsonp({ callback: 'callback' }), 'posts.show');
app.get('/api/posts', app.jsonp({ callback: 'cb' }), 'posts.list');
};
By default, XSS is not defended when responding JSONP, and, in some cases, it is quite dangerous. We classify JSONP APIs into three type grossly:
If our JSONP API provides the last two type services and, without any XSS defense, user sensitive data may be leaked and even user may be phished. Given this, the framework supports the validations of CSRF and referrer by default.
In the JSONP configuration, we could enable the CSRF validation for JSONP APIs simply by setting csrf: true.
// config/config.default.js
module.exports = {
jsonp: {
csrf: true,
},
};
Note: the CSRF validation depends on the Cookie based CSRF validation provided by security.
When the CSRF validation is enabled, the client should bring CSRF token as well when it sends a JSONP request, if the page where the JSONP sender belongs to shares the same domain with our services, CSRF token in Cookie can be read(CSRF can be set manually if it is absent), and is brought together with the request.
The CSRF way can be used for JSONP request validation only if the main domains are the same, while providing JSONP services for pages in different domains, we can limit JSONP senders into a controllable rang by configuring the referrer whitelist.
//config/config.default.js
exports.jsonp = {
whiteList: /^https?:\/\/test.com\//,
// whiteList: '.test.com',
// whiteList: 'sub.test.com',
// whiteList: [ 'sub.test.com', 'sub2.test.com' ],
};
whileList can be configured as regular expression, string and array:
^ and tail \/ which guarantees the whole domain matches.exports.jsonp = {
whiteList: /^https?:\/\/test.com\//,
};
// matches referrer:
// https://test.com/hello
// http://test.com/
., e.g. .test.com, the referrer whitelist indicates all sub-domains of test.com, test.com itself included. if the string does not begin with a ., e.g. sub.test.com, it indicates sub.test.com one domain only. (both HTTP and HTTPS are supported)exports.jsonp = {
whiteList: '.test.com',
};
// matches domain test.com:
// https://test.com/hello
// http://test.com/
// matches subdomain
// https://sub.test.com/hello
// http://sub.sub.test.com/
exports.jsonp = {
whiteList: 'sub.test.com',
};
// only matches domain sub.test.com:
// https://sub.test.com/hello
// http://sub.test.com/
exports.jsonp = {
whiteList: [ 'sub.test.com', 'sub2.test.com' ],
};
// matches domain sub.test.com and sub2.test.com:
// https://sub.test.com/hello
// http://sub2.test.com/
If both CSRF and referrer validation are enabled, the request sender passes any one of them passes the JSONP security validation.
We identify the request success or not, in which state by the status code and set response content in the body. By setting the response header, extended information can be set as well.
context.set(key, value) sets one response header and context.set(headers) sets many in one time.
// app/controller/api.js
const Controller = require('beidou').Controller;
module.exports = class ProxyController extends Controller {
* show() {
const ctx = this.ctx;
const start = Date.now();
ctx.body = yield ctx.service.post.get();
const used = Date.now() - start;
// set one response header
ctx.set('show-response-time', used.toString());
}
};
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