bpmn-server / Listener

Class: Listener#

The server's event bus. Its legacy face is a Node EventEmitter: on(event, fn) listeners run synchronously within the engine's step, and one that throws aborts it, as before. Its lifecycle face (subscribe) is awaited after them, each subscriber isolated: a failure is reported to onSubscriberError (the server's logger) and the execution continues (lifecycle.ts).

Hierarchy#

EventEmitter

↳ Listener

Table of contents#

Constructors#

constructor

Properties#

Methods#

Constructors#

constructor#

• new Listener(options?): Listener

Parameters#

Name	Type
`options?`	`EventEmitterOptions`

Returns#

Listener

Inherited from#

EventEmitter.constructor

Defined in#

node_modules/@types/node/events.d.ts:54

Properties#

lifecycleListeners#

• Private Readonly lifecycleListeners: Set\<ILifecycleListener>

Defined in#

packages/bpmn-server/src/server/Listener.ts:11

onSubscriberError#

• onSubscriberError: (error: unknown, event: string) => void

Where a subscriber's failure goes; the server sets its logger's.

Type declaration#

▸ (error, event): void

Parameters#

Name	Type
`error`	`unknown`
`event`	`string`

Returns#

void

Defined in#

packages/bpmn-server/src/server/Listener.ts:13

Methods#

[captureRejectionSymbol]#

▸ [captureRejectionSymbol](error, event, ...args): void

The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

import { EventEmitter, captureRejectionSymbol } from 'node:events';

class MyClass extends EventEmitter {
  constructor() {
    super({ captureRejections: true });
  }

  [captureRejectionSymbol](err, event, ...args) {
    console.log('rejection happened for', event, 'with', err, ...args);
    this.destroy(err);
  }

  destroy(err) {
    // Tear the resource down here.
  }
}

Parameters#

Name	Type
`error`	`Error`
`event`	`string` \| `symbol`
`...args`	`any`[]

Returns#

void

Since

v13.4.0, v12.16.0

Inherited from#

EventEmitter.[captureRejectionSymbol]

Defined in#

node_modules/@types/node/events.d.ts:87

addListener#

▸ addListener\<E>(eventName, listener): this

Alias for emitter.on(eventName, listener).

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns#

this

Since

v0.1.26

Inherited from#

EventEmitter.addListener

Defined in#

node_modules/@types/node/events.d.ts:92

emit#

▸ emit\<E>(eventName, ...args): boolean

Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();

// First listener
myEmitter.on('event', function firstListener() {
  console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
  console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
  const parameters = args.join(', ');
  console.log(`event with parameters ${parameters} in third listener`);
});

console.log(myEmitter.listeners('event'));

myEmitter.emit('event', 1, 2, 3, 4, 5);

// Prints:
// [
//   [Function: firstListener],
//   [Function: secondListener],
//   [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`
`...args`	`any`[]

Returns#

boolean

Since

v0.1.26

Inherited from#

EventEmitter.emit

Defined in#

node_modules/@types/node/events.d.ts:134

eventNames#

▸ eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns#

(string | symbol)[]

Since

v6.0.0

Inherited from#

EventEmitter.eventNames

Defined in#

node_modules/@types/node/events.d.ts:154

getMaxListeners#

▸ getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to events.defaultMaxListeners.

Returns#

number

Since

v1.0.0

Inherited from#

EventEmitter.getMaxListeners

Defined in#

node_modules/@types/node/events.d.ts:161

listenerCount#

▸ listenerCount\<E>(eventName, listener?): number

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event being listened for
`listener?`	(...`args`: `any`[]) => `void`	The event handler function

Returns#

number

Since

v3.2.0

Inherited from#

EventEmitter.listenerCount

Defined in#

node_modules/@types/node/events.d.ts:170

listeners#

▸ listeners\<E>(eventName): (...args: any[]) => void[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`

Returns#

(...args: any[]) => void[]

Since

v0.1.26

Inherited from#

EventEmitter.listeners

Defined in#

node_modules/@types/node/events.d.ts:186

off#

▸ off\<E>(eventName, listener): this

Alias for emitter.removeListener().

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns#

this

Since

v10.0.0

Inherited from#

EventEmitter.off

Defined in#

node_modules/@types/node/events.d.ts:191

on#

▸ on\<E>(eventName, listener): this

Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.on('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns#

this

Since

v0.1.101

Inherited from#

EventEmitter.on

Defined in#

node_modules/@types/node/events.d.ts:225

once#

▸ once\<E>(eventName, listener): this

Adds a one-time listener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns#

this

Since

v0.3.0

Inherited from#

EventEmitter.once

Defined in#

node_modules/@types/node/events.d.ts:256

prependListener#

▸ prependListener\<E>(eventName, listener): this

Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventName and listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns#

this

Since

v6.0.0

Inherited from#

EventEmitter.prependListener

Defined in#

node_modules/@types/node/events.d.ts:275

prependOnceListener#

▸ prependOnceListener\<E>(eventName, listener): this

Adds a one-time listener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type	Description
`eventName`	`string` \| `symbol`	The name of the event.
`listener`	(...`args`: `any`[]) => `void`	The callback function

Returns#

this

Since

v6.0.0

Inherited from#

EventEmitter.prependOnceListener

Defined in#

node_modules/@types/node/events.d.ts:292

rawListeners#

▸ rawListeners\<E>(eventName): (...args: any[]) => void[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`

Returns#

(...args: any[]) => void[]

Since

v9.4.0

Inherited from#

EventEmitter.rawListeners

Defined in#

node_modules/@types/node/events.d.ts:326

removeAllListeners#

▸ removeAllListeners\<E>(eventName?): this

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName?`	`string` \| `symbol`

Returns#

this

Since

v0.1.26

Inherited from#

EventEmitter.removeAllListeners

Defined in#

node_modules/@types/node/events.d.ts:338

removeListener#

▸ removeListener\<E>(eventName, listener): this

Removes the specified listener from the listener array for the event named eventName.

const callback = (stream) => {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() in progress. Subsequent events behave as expected.

import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();

const callbackA = () => {
  console.log('A');
  myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
  console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
//   A
//   B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
//   A

Because listeners are managed using an internal array, calling this will change the position indexes of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping') listener is removed:

import { EventEmitter } from 'node:events';
const ee = new EventEmitter();

function pong() {
  console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Type parameters#

Name	Type
`E`	extends `string` \| `symbol`

Parameters#

Name	Type
`eventName`	`string` \| `symbol`
`listener`	(...`args`: `any`[]) => `void`

Returns#

this

Since

v0.1.26

Inherited from#

EventEmitter.removeListener

Defined in#

node_modules/@types/node/events.d.ts:425

setMaxListeners#

▸ setMaxListeners(n): this

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters#

Name	Type
`n`	`number`

Returns#

this

Since

v0.3.5

Inherited from#

EventEmitter.setMaxListeners

Defined in#

node_modules/@types/node/events.d.ts:436

clearSubscriptions#

▸ clearSubscriptions(): void

Returns#

void

Defined in#

packages/bpmn-server/src/server/Listener.ts:15

▸ subscribe(listener): () => void

Parameters#

Name	Type
`listener`	`ILifecycleListener`

Returns#

fn

▸ (): void

Returns#

void

Defined in#

packages/bpmn-server/src/server/Listener.ts:17

dispatch#

▸ dispatch(event, payload): Promise\<void>

Emits event to the legacy listeners and then to all, then notifies each lifecycle subscriber in turn.

Parameters#

Name	Type
`event`	`string`
`payload`	`Object`
`payload.event`	`string`
`payload.context`	`any`
`payload.eventDetails?`	`unknown`

Returns#

Promise\<void>

Defined in#

packages/bpmn-server/src/server/Listener.ts:23

doEvent#

▸ doEvent(event, execution, item?, eventDetails?): Promise\<void>

Parameters#

Name	Type	Default value
`event`	`any`	`undefined`
`execution`	`any`	`undefined`
`item`	`any`	`null`
`eventDetails`	`Object`	`{}`

Returns#

Promise\<void>

Deprecated

The engine dispatches through dispatch; kept for callers of the earlier form.

Defined in#

packages/bpmn-server/src/server/Listener.ts:37