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Last pushed: 2 months ago
Short Description
Template for writing mu.semte.ch services in JavaScript using Express 4
Full Description

Mu Javascript template

Template for writing mu.semte.ch services in JavaScript using Express 4

Getting started

Create a new folder. Add the following Dockerfile:

FROM semtech/mu-javascript-template
MAINTAINER Aad Versteden <madnificent@gmail.com>

Create your microservice in app.js:

import { app, query } from 'mu';

app.get('/', function( req, res ) {
  res.send('Hello mu-javascript-template');
} );


app.get('/query', function( req, res ) {
  var myQuery = `
    SELECT *
    WHERE {
      GRAPH <http://mu.semte.ch/application> {
        ?s ?p ?o.
      }
    }`;

  query( myQuery )
    .then( function(response) {
      res.send( JSON.stringify( response ) );
    })
    .catch( function(err) {
      res.send( "Oops something went wrong: " + JSON.stringify( err ) );
    });
} );

Check Express' Getting Started guide to learn how to build a REST API in Express.

Requirements

  • database link: You need a link to the database which exposes a SPARQL endpoint on http://database:8890/sparql. In line with other microservices.

Imports

The following importable variables are available:

  • app: The Express application on which routes can be added
  • query(query) => Promise: Function for sending queries to the triplestore
  • update(query) => Promise: Function for sending updates to the triplestore
  • uuid() => string: Generates a random UUID
  • sparql: Template tag to create queries with interpolated values
  • sparqlEscapeString(value) => string: Function to escape a string in SPARQL
  • sparqlEscapeUri(value) => string: Function to escape a URI in SPARQL
  • sparqlEscapeInt(value) => string: Function to escape an integer in SPARQL
  • sparqlEscapeFloat(value) => string: Function to escape a float in SPARQL
  • sparqlEscapeDate(value) => string: Function to escape a date in SPARQL
  • sparqlEscapeDateTime(value) => string: Function to escape a datetime in SPARQL
  • sparqlEscapeBool(value) => string: Function to escape a boolean in SPARQL
  • sparqlEscape(value, type) => string: Function to escape a value in SPARQL according to the given type. Type must be one of 'string', 'uri', 'int', 'float', 'date', 'dateTime', 'bool'.

You can either import specific attributes from the mu library, or import the whole mu object.

An example of importing specific variables:

import { app, query } from 'mu';

app.get('/', function( req, res ) {
  res.send('Hello mu-javascript-template');
} );

An example of importing the whole library:

import mu from 'mu';

mu.app.get('/', function( req, res ) {
  res.send('Hello using full import');
} );

Dependencies

You can install additional dependencies by including a package.json file next to your app.js. It works as you would expect: just define the packages in the dependencies section of the package.json. They will be installed automatically at build time.

Developing with the template

When developing, you can use the template image, mount the volume with your sources in /app and add a link to the database. Set the NODE_ENV environment variable to development. The service will live-reload on changes. You'll need to restart the container when you define additional dependencies in your package.json.

docker run --link virtuoso:database \
       -v `pwd`:/app \
       -p 8888:80 \
       -e NODE_ENV=development \
       --name my-js-test \
       semtech/mu-javascript-template
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semtech

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