A Module for composing full page layouts out of page fragments in a micro frontend architecture.
See the official Podium documentation site.
Module for building a layout server. A layout server is mainly responsible for fetching HTML fragments and stitching these fragments into an full HTML page.
To do this, a layout instance provides three core features:
@podium/clientused to fetch content from podlets@podium/contextused to set request bound information on the requests from the layout to podlets when fetching their content@podium/proxymakes it possible to publicly expose data endpoints in a podlet or in any backend service
This module can be used together with a plain node.js HTTP server or any HTTP framework and any templating language of your choosing (or none if you prefer).
Note: Connect compatible middleware based frameworks (such as Express) are considered
first class in Podium so this module provides a .middleware() method for
convenience.
For writing layout servers with other HTTP frameworks the following modules exist:
$ npm install @podium/layoutBuild a simple layout server including a single podlet using Express:
import express from 'express';
import Layout from '@podium/layout';
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
const podlet = layout.client.register({
name: 'myPodlet',
uri: 'http://localhost:7100/manifest.json',
});
const app = express();
app.use(layout.middleware());
app.get('/', (req, res, next) => {
const ctx = res.locals.podium.context;
Promise.all([podlet.fetch(ctx)]).then((result) => {
res.status(200).send(`
<html><body>
<section>${result[0]}</section>
</body></html>
`);
});
});
app.listen(7000);Create a new Layout instance.
const layout = new Layout(options);| option | default | type | required | details |
|---|---|---|---|---|
| name | null |
string |
true |
Name that the layout identifies itself by |
| pathname | null |
string |
true |
Pathname of where a Layout is mounted in a http server |
| logger | null |
object |
false |
A logger which conform to a log4j interface |
| context | null |
object |
false |
Options to be passed on to the internal @podium/context constructor |
| client | null |
object |
false |
Options to be passed on to the internal @podium/client constructor |
| proxy | null |
object |
false |
Options to be passed on to the internal @podium/proxy constructor |
Name that the layout identifies itself by. The name value must be in camelCase.
Example:
const layout = new Layout({
name: 'myLayoutName',
pathname: '/foo',
});The Pathname of where the Layout is mounted into the HTTP server. It is important that this value matches where the entry point of a route is in the HTTP server since this value is used to mount the proxy and tell podlets (through the context) where they are mounted and where the proxy is mounted.
If the layout is mounted at the server "root", set pathname to /:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
app.use(layout.middleware());
app.get('/', (req, res, next) => {
[ ... ]
});If the layout is mounted at /foo, set pathname to /foo:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
});
app.use('/foo', layout.middleware());
app.get('/foo', (req, res, next) => {
[ ... ]
});
app.get('/foo/:id', (req, res, next) => {
[ ... ]
});There is also a helper method for retrieving the set pathname which can be
used to get the pathname from the Layout object when defining routes.
See .pathname() for further details.
Any log4j compatible logger can be passed in and will be used for logging. Console is also supported for easy test / development.
Example:
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
logger: console,
});Under the hood abslog is used to abstract out logging. Please see abslog for further details.
Options to be passed on to the internal [@podium/context constructor].
Please see the [@podium/context constructor] for which options can be set.
Example of setting the debug context to default true:
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
context: {
debug: {
enabled: true,
},
},
});Options to be passed on to the internal @podium/client constructor.
Please see @podium/client constructor for which options which can be set.
Example of setting the retries on the client to 6:
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
client: {
retries: 6,
},
});Options to be passed on to the internal @podium/proxy constructor.
Please see @podium/proxy constructor for which options which can be set.
Example of setting the timeout on the proxy to 30 seconds:
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
proxy: {
timeout: 30000,
},
});The Layout instance has the following API:
Method for processing an incoming HTTP request. This method is intended to be used to implement support for multiple HTTP frameworks and it should not normally be necessary to use this method directly when creating a layout server.
What it does:
- Runs @podium/context parsers on the incoming request and sets an object with the context at
HttpIncoming.contextwhich can be passed on to the client when requesting content from podlets. - Mounts the @podium/proxy so each podlet can do transparent proxy requests if needed.
Returns a Promise. If the inbound request matches a proxy endpoint the returned
Promise will resolve with undefined. If the inbound request does not match a
proxy endpoint the returned Promise will resolve with the passed in
HttpIncoming object.
The method takes the following arguments:
An instance of an HttpIncoming class.
import { HttpIncoming } from '@podium/utils';
import Layout from '@podium/layout';
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
app.use(async (req, res, next) => {
const incoming = new HttpIncoming(req, res, res.locals);
try {
const result = await layout.process(incoming);
if (result) {
res.locals.podium = result;
next();
}
} catch (error) {
next(error);
}
});| option | default | type | required | details |
|---|---|---|---|---|
| context | true |
boolean |
false |
If @podium/context should be applied as part of the .process() method |
| proxy | true |
boolean |
false |
If @podium/proxy should be applied as part of the .process() method |
This method is intended to be used to implement support for multiple HTTP frameworks and it should not normally be necessary to use this method directly when creating a layout server.
This method is used by .podiumSend() when using the Express HTTP framework.
The method takes the following arguments:
An instance of the HttpIncoming class.
import { HttpIncoming } from '@podium/utils';
import Layout from '@podium/layout';
import express from 'express';
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
const app = express();
app.get('/', (req, res) => {
const incoming = new HttpIncoming(req, res, res.locals);
layout.render(incoming, '<div>content to render</div>');
});An HTML string or an object with the following shape:
data.title- document titledata.locale- language tag/locale identifier defaults toen-USdata.encoding- defaults toutf-8data.head- Any additional HTML markup that should be placed in the document<head>data.js- JavaScript URL, will be used as asrcvalue in a script tagdata.css- CSS URL, will be used as anhrefvalue in a link tagdata.body- HTML body markup to be rendered
Using a string
layout.render(incoming, '<div>content to render</div>');Using a data object
layout.render(incoming, {
title: 'my doc title',
body: '<div>my content</div>',
});A Connect compatible middleware which takes care of the operations needed for
a layout to fully work. This method is more or less a wrapper for the .process() method.
Important: This middleware must be mounted before defining any routes.
Example
const app = express();
app.use(layout.middleware());The context generated by the middleware will be stored at
res.locals.podium.context.
Returns an Array of internal middleware performing the tasks described above.
A helper method to retrieve the pathname set on the constructor. This can be
handy to use in defining routes since the pathname set in the constructor
must match whatever is defined as root in each route in a HTTP router.
Example:
const layout = new Layout({
name: 'myLayout',
pathname: '/foo'
});
app.get(layout.pathname(), (req, res, next) => {
[ ... ]
});
app.get(`${layout.pathname()}/bar`, (req, res, next) => {
[ ... ]
});
app.get(`${layout.pathname()}/bar/:id`, (req, res, next) => {
[ ... ]
});Sets the pathname for a Layout's JavaScript assets.
options can be either an object or an array of options objects as described below.
When a value is set it will be kept internally and returned when the method is called again.
| option | type | default | required |
|---|---|---|---|
| value | string |
||
| prefix | boolean |
false |
|
| type | string |
default |
Used to set the pathname for the JavaScript assets for the Layout. The value can be a URL at which the Layout's user facing JavaScript is served. The value can be the [pathname] of a [URL] or an absolute URL.
Examples:
Serve a javascript file at /assets/main.js:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
layout.js({ value: '/assets/main.js' });
// or
layout.js([{ value: '/assets/main.js' }, { value: '/assets/secondary.js' }]);Serve assets statically along side the app and set a relative URI to the JavaScript file:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
app.use('/assets', express.static('./app/files/assets'));
layout.js({ value: '/assets/main.js' });Set an absolute URL to where the JavaScript file is located:
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
layout.js({ value: 'http://cdn.mysite.com/assets/js/e7rfg76.js' });Specify whether the method should prefix the return value with the value for
pathname set in the constructor.
Examples:
Return the full pathname, /foo/assets/main.js, to the JavaScript assets:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
});
layout.js({ value: '/assets/main.js', prefix: true });Prefix will be ignored if the returned value is an absolute URL.
Set the type of script which is set. default indicates an unknown type.
module inidcates as ES6 module.
Sets the pathname for a Layout's CSS assets.
options can be either an object or an array of options objects as described below.
When a value is set it will be kept internally and returned when the method is called again.
| option | type | default | required |
|---|---|---|---|
| value | string |
||
| prefix | boolean |
false |
Used to set the pathname for the CSS assets for the Layout. The value can be a URL at which the Layout's user facing CSS is served. The value can be the [pathname] of a [URL] or an absolute URL.
The value can be set only once. If called multiple times with a value, the method will throw. The method can be called multiple times to retrieve the value though.
Examples:
Serve a CSS file at /assets/main.css:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
layout.css({ value: '/assets/main.css' });
// or
layout.css([{ value: '/assets/main.css' }, { value: '/assets/secondary.css' }]);Serve assets from a static file server and set a relative URI to the CSS file:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
app.use('/assets', express.static('./app/files/assets'));
layout.css({ value: '/assets/main.css' });Set an absolute URL to where the CSS file is located:
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
layout.css({ value: 'http://cdn.mysite.com/assets/css/3ru39ur.css' });Sets whether the method should prefix the return value with the value for
pathname set in the constructor.
Examples:
Return the full pathname (/foo/assets/main.css) to the CSS assets:
const app = express();
const layout = new Layout({
name: 'myLayout',
pathname: '/foo',
});
layout.css({ value: '/assets/main.css', prefix: true });Prefix will be ignored if the returned value is an absolute URL
Override the default encapsulating HTML document.
Takes a function with the following shape:
layout.view(data => `<!doctype html>
<html lang="${data.locale}">
<head>
<meta charset="${data.encoding}">
<title>${data.title}</title>
<link href="${data.css}" rel="stylesheet">
<script src="${data.js}" defer></script>
${data.head}
</head>
<body>
${data.body}
</body>
</html>`;
);Method on the http.ServerResponse object for sending an HTML fragment. Calls
the send / write method on the http.ServerResponse object.
This method will wrap the provided fragment in a default HTML document before dispatching.
You can use the .view() method to disable using a template or to set a custom template.
Example of sending an HTML fragment:
app.get(layout.pathname(), (req, res) => {
res.podiumSend('<h1>Hello World</h1>');
});Example of sending additional content with an HTML fragment:
app.get(layout.pathname(), (req, res) => {
res.podiumSend({
title: 'Document title',
head: '<script src="additional-script.js" defer></script>',
body: '<h1>Hello World</h1>',
});
});A property that exposes an instance of the @podium/client for fetching content from podlets.
Example of registering a podlet and fetching it:
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
const podlet = layout.client.register({
name: 'myPodlet',
uri: 'http://localhost:7100/manifest.json',
});
podlet.fetch({}).then((result) => {
console.log(result);
});Please see @podium/client for full documentation.
A property that exposes an instance of the @podium/context used to create a context.
Example of registering a custom third party context parser to the context:
import Parser from 'my-custom-parser';
const layout = new Layout({
name: 'myLayout',
pathname: '/',
});
layout.context.register('customParser', new Parser('someConfig'));Please see @podium/context for full documentation.
Property that exposes a metric stream. This stream joins all internal metrics streams into one stream resulting in all metrics from all sub modules being exposed here.
Please see @metrics/metric for full documentation.
Copyright (c) 2019 FINN.no
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