HTTP-PROBLEM

Provides a simple implementation of the HTTP Problem Spec (JSON format only).

See: https://tools.ietf.org/html/draft-ietf-appsawg-http-problem

Note: Use v0.1.0 for Node v0.12.x. With v0.2.0, the code starts to make use of newer ES6 features.

npm install http-problem

Nothing really all that fancy here. There are a few ways to create a problem object:

The following creates a simple default problem for an HTTP status code

var Problem = require('http-problem');
var badrequest = Problem.BADREQUEST.raise();
throw badrequest;

You can define then throw your own problem types:

var NoCreditType = new Problem.Type(
  'http://example.com/probs/out-of-credit',
  'You do not have enough credit.',
  {status:400});

NoCreditType.throw({
  detail: 'Your current balance is 30, but that costs 50.',
  instance: 'http://example.net/account/12345/msgs/abc',
  balance: 30,
  accounts: [
    'http://example.net/account/12345',
    'http://example.net/account/67890']
});

Standard connect middleware is provided. The middleware intercepts Problem objects thrown as exceptions and serializes them appropriately in the HTTP response.

var express = require('express');
var server = express();

var router = express.Router();
router.get('/', function(req,res) {
  Problem.GONE.throw();
});
router.use(Problem.middleware);
server.use('/',router).listen(8888);

Use the problem.wrap method to parse out a received problem:

var Problem = require('http-problem');

var obj = {
  type: 'http://example.org',
  status: 400
};

var problem = problem.wrap(obj);

// or
var str = JSON.stringify(obj);
problem = problem.wrap(str); // wrap from string

API

Constructor: Problem([type][, options])

Constructor for new Problem instances

• type - either a Problem.Type instance or string with an absolute URL. Defaults to Problem.BLANK if unspecified. identifying the error
• options
  • status - HTTP Status Code
  • detail - Human readable explanation of the problem that is specific to this instance.
  • instance - An Absolute URL identifying the specific occurence of the problem.

Additional extension properties may be included as values on the options. When passed, these will become constant values on the generated Problem object

Property: <string> Problem.prototype.type

Returns an absolute URL identifying the Problem type.

Property: <string> Problem.prototype.title

Returns the Problem title.

Property: <number> Problem.prototype.status

Returns the HTTP Status code for this problem.

Property: <string> Problem.prototype.detail

Returns a human readable explanation specific to this instance of the problem.

Property: <string> Problem.prototype.instance

Returns an absolute URL identifying the specific occurence of the problem.

Method: <void> Problem.prototype.send(res)

Sends the Problem on the HTTP Response. The res parameter is assumed to be an Express-style response object. The implementation of the send method is:

function(res) {
  var status = this.status || 400;
  res.setHeader('Content-Type', 'application/problem+json');
  res.status(status).json(this);
};

Class Method: <constructor> Problem.create()

Create a new Problem class, allowing you to create your own Problem subclasses.

var MyProblem = Problem.create();
var myProblem = new MyProblem(Problem.BLANK);
myProblem.throw();

Class Method: <boolean> Problem.registerProblemType(type)

Register a custom Problem.Type

var NoCreditType =
  new Problem.Type(
    'http://example.com/probs/out-of-credit',
    'You do not have enough credit.',
    {status:400});
Problem.registerProblemType(NoCreditType);

Class Method: <boolean> Problem.registerProblemType(uri[, title])

Register a custom Problem.Type

Problem.registerProblemType(
  'http://example.com/probs/out-of-credit',
  'You do not have enough credit.');

Class Method: <Problem.Type> Problem.lookupProblemType(uri)

Lookup a registered custom Problem.Type

Class Method: <Problem.Type> Problem.forStatus(status)

Lookup the Problem.Type for a specific HTTP status code

Class Method: <Problem> Problem.wrap(obj)

Wrap a JavaScript object as a Problem.

Class Method: <Problem> Problem.wrap(str)

Parse the JSON string and wrap the resulting object as a Problem.

Class Property: <function> Problem.middleware

Connect style middleware that can be used to intercept Problems thrown as errors and serialize them correctly on an HTTP response.

var express = require('express');
var server = express();

var router = express.Router();
router.get('/', function(req,res) {
  Problem.GONE.throw();
});
router.use(Problem.middleware);
server.use('/',router).listen(8888);

Constructor: Problem.Type(url[, title][, options])

Creates a new Problem.Type.

• url - The absolute URL identifying the problem type.
• title - The common title of the proble.
• options -
  • status - The default HTTP status code for problems of this type.
  • ins - The instance constructor for problems of this type.

var MyType = new Problem.Type(
  'http://example.org', 'MyProblem', {status:400});
MyType.throw();

Property: <string> Problem.Type.prototype.type

The absolute URL identifying the problem type.

Property: <string> Problem.Type.prototype.title

The common title of the problem type.

Property: <number> Problem.Type.prototype.status

The default HTTP status code for problems of this type.

Method: <void> Problem.Type.prototype.throw([options])

Create a new instance of this problem type and throw it as an Error. The options argument is the same as the options for the Problem constructor.

Method: <Problem> Problem.Type.prototype.raise([options])

Create a new instance of this problem type and return it. The options argument is the same as the options for the Problem constructor.

Method: <void> Problem.Type.prototype.reject([options])

Create a new instance of this problem type and create a rejected Promise with the Error. The options argument is the same as the options for the Problem constructor.

Constants:

• <Problem.Type> Problem.BLANK - The about:blank Problem Type
• <Problem.Type> Problem.OK
• <Problem.Type> Problem.CREATED
• <Problem.Type> Problem.ACCEPTED
• <Problem.Type> Problem.NON_AUTHORITATIVE_INFORMATION
• <Problem.Type> Problem.NO_CONTENT
• <Problem.Type> Problem.RESET_CONTENT
• <Problem.Type> Problem.PARTIAL_CONTENT
• <Problem.Type> Problem.MULTIPLE_CHOICES
• <Problem.Type> Problem.MOVED_PERMANENTLY
• <Problem.Type> Problem.FOUND
• <Problem.Type> Problem.SEE_OTHER
• <Problem.Type> Problem.NOT_MODIFIED
• <Problem.Type> Problem.USE_PROXY
• <Problem.Type> Problem.TEMPORARY_REDIRECT
• <Problem.Type> Problem.BAD_REQUEST
• <Problem.Type> Problem.UNAUTHORIZED
• <Problem.Type> Problem.PAYMENT_REQUIRED
• <Problem.Type> Problem.FORBIDDEN
• <Problem.Type> Problem.NOT_FOUND
• <Problem.Type> Problem.METHOD_NOT_ALLOWED
• <Problem.Type> Problem.NOT_ACCEPTABLE
• <Problem.Type> Problem.PROXY_AUTHENTICATION_REQUIRED
• <Problem.Type> Problem.REQUEST_TIMEOUT
• <Problem.Type> Problem.CONFLICT
• <Problem.Type> Problem.GONE
• <Problem.Type> Problem.LENGTH_REQUIRED
• <Problem.Type> Problem.PRECONDITION_FAILED
• <Problem.Type> Problem.REQUEST_ENTITY_TOO_LARGE
• <Problem.Type> Problem.REQUEST_URI_TOO_LONG
• <Problem.Type> Problem.UNSUPPORTED_MEDIA_TYPE
• <Problem.Type> Problem.REQUESTED_RANGE_NOT_SATISFIABLE
• <Problem.Type> Problem.EXPECTATION_FAILED
• <Problem.Type> Problem.UNPROCESSABLE_ENTITY
• <Problem.Type> Problem.TOO_MANY_REQUESTS
• <Problem.Type> Problem.INTERNAL_SERVER_ERROR
• <Problem.Type> Problem. NOT_IMPLEMENTED
• <Problem.Type> Problem.BAD_GATEWAY
• <Problem.Type> Problem.SERVICE_UNAVAILABLE
• <Problem.Type> Problem.GATEWAY_TIMEOUT
• <Problem.Type> Problem.HTTP_VERSION_NOT_SUPPORTED