The 'jayson' npm package is a JSON-RPC 2.0/1.0 compliant server and client library for Node.js. It allows you to create JSON-RPC servers and clients, making it easy to implement remote procedure calls (RPC) in a standardized way.
Creating a JSON-RPC Server
This code creates a JSON-RPC server with a single method 'add' that takes two arguments and returns their sum. The server listens on port 3000.
const jayson = require('jayson');
const server = jayson.server({
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
});
server.http().listen(3000);Creating a JSON-RPC Client
This code creates a JSON-RPC client that connects to a server running on 'http://localhost:3000'. It makes a request to the 'add' method with arguments [1, 1] and logs the result.
const jayson = require('jayson');
const client = jayson.client.http('http://localhost:3000');
client.request('add', [1, 1], function(err, response) {
if(err) throw err;
console.log(response.result); // 2
});Batch Requests
This code demonstrates how to make batch requests using the JSON-RPC client. It sends two 'add' requests in a single batch and logs the responses.
const jayson = require('jayson');
const client = jayson.client.http('http://localhost:3000');
const batch = [
client.request('add', [1, 1], null, false),
client.request('add', [2, 2], null, false)
];
client.request(batch, function(err, responses) {
if(err) throw err;
console.log(responses); // [{jsonrpc: '2.0', result: 2, id: 1}, {jsonrpc: '2.0', result: 4, id: 2}]
});The 'jsonrpc-lite' package is a lightweight JSON-RPC 2.0 library for Node.js. It provides a simple and minimalistic approach to creating JSON-RPC servers and clients. Compared to 'jayson', 'jsonrpc-lite' is more lightweight but may lack some of the advanced features and flexibility that 'jayson' offers.
The 'node-json-rpc' package is another JSON-RPC 2.0 library for Node.js. It provides a straightforward way to create JSON-RPC servers and clients. While it offers similar functionalities to 'jayson', it may have a different API design and might not be as feature-rich.
The 'json-rpc2' package is a JSON-RPC 2.0 library for Node.js that supports both client and server implementations. It is similar to 'jayson' in terms of functionality but may have different design choices and API conventions.
Jayson is a JSON-RPC 2.0 and 1.0 compliant server and client written in JavaScript for node.js that aims to be as simple as possible to use.
A basic JSON-RPC 2.0 server via HTTP:
Server example in examples/simple_example/server.js:
const jayson = require('jayson');
// create a server
const server = new jayson.server({
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
});
server.http().listen(3000);
Client example in examples/simple_example/client.js invoking add on the above server:
const jayson = require('jayson');
// create a client
const client = new jayson.client.http({
port: 3000
});
// invoke "add"
client.request('add', [1, 1], function(err, response) {
if(err) throw err;
console.log(response.result); // 2
});
Install the latest version of jayson from npm by executing npm install jayson in your shell. Do a global install with npm install --global jayson if you want the jayson client CLI in your PATH.
collect option removed from jayson.Server/Method. JSON-RPC params to handlers are now always in the first argument.collect: true is now the default option for a new jayson.Server and jayson.MethodThere is a basic CLI client in bin/jayson.js and it should be available as jayson in your shell if you installed the package globally. Run jayson --help to see how it works.
Jayson does not have any special dependencies that cannot be resolved with a simple npm install. It is being continuously tested using travis-ci. You can look inside .travis.yml if you want to see which versions are tested against.
In addition to this document, a comprehensive class documentation made with jsdoc is available at jayson.tedeh.net.
npm install --devnpm run testSince v2.1.0 there is experimental typescript support available with jayson.
If you have a problem with the type definitions, see the Contributing section.
The client is available as the Client or client property of require('jayson').
| Name | Description |
|---|---|
Client | Base class |
Client.tcp | TCP interface |
Client.tls | TLS interface |
Client.http | HTTP interface |
Client.https | HTTPS interface |
Client.browser | Browser interface |
Every client supports these options:
| Option | Default | Type | Description |
|---|---|---|---|
reviver | undefined | Function | JSON.parse reviver |
replacer | undefined | Function | JSON.stringify replacer |
generator | RFC4122 generator | Function | Generates a String for request ID. |
version | 2 | Number | JSON-RPC version to support (1 or 2) |
notificationIdNull | false | Boolean | Since 3.6.1. When true "id" property of a request will be set to null when version 2. |
Uses the same options as http.request in addition to these options:
| Option | Default | Type | Description |
|---|---|---|---|
encoding | utf8 | String | Determines the encoding to use |
headers | undefined | Object | Extend the headers sent by the client |
The HTTP client will emit the following events:
| Event | When | Arguments | Notes |
|---|---|---|---|
http request | Created an HTTP request | 1. Instance of http.ClientRequest | |
http response | Received an HTTP response | 1. Instance of http.IncomingMessage 2. Instance of http.ClientRequest | |
http error | Underlying stream emits error | 1. Error | |
http timeout | Underlying stream emits timeout | Automatically causes the request to abort |
It is possible to pass a string URL as the first argument. The URL will be run through url.parse. Example:
const jayson = require('jayson');
const client = new jayson.client.http('http://localhost:3000');
// client.options is now the result of url.parse
Uses the same options as https.request in addition to the same options as Client.http. This means it is also possible
to pass a string URL as the first argument and have it interpreted by url.parse.
Will emit the same custom events as Client.http.
Uses the same options as net.connect.
Since version 3.5.1
The TCP client will emit the following events:
| Event | When | Arguments | Notes |
|---|---|---|---|
| tcp socket | TCP socket is opened | 1. net.Socket | Can be used to setup timeouts |
| tcp error | TCP socket emits error | 1. Error emit by net.Socket |
Uses the same options as tls.connect.
Since version 3.5.1
The TLS client will emit the following events:
| Event | When | Arguments | Notes |
|---|---|---|---|
| tcp socket | TCP socket is opened | 1. net.Socket | Can be used to setup timeouts |
| tcp error | TCP socket emits error | 1. Error emit by net.Socket |
The browser client is a simplified version of the regular client for use browser-side. It does not have any dependencies on node.js core libraries, but does depend on the uuid package for generating request ids. It also does not know how to "send" a request to a server like the other clients.
Because it does not depend on any core libraries, the browser client is not an instance of JaysonClient or EventEmitter and therefore does not emit any of the normal request events that the other clients do.
To use the browser client, require('jayson/lib/client/browser') and pass a calling/transport function as the first argument. The transport function receives a JSON-RPC string request and is expected to callback with a string response received from the server (not JSON) or an error (not a JSON-RPC error).
The reason for dealing with strings is to support the reviver and replacer options like the other clients.
This client example in examples/browser_client/client.js below uses node-fetch in the transport function, but a dropin replacement for use in an actual browser could instead use whatwg-fetch.
The browser client has a separate TypeScript type declaration available in jayson/lib/client/browser/index.d.ts which depends on the main Jayson type declaration.
'use strict';
const jaysonBrowserClient = require('jayson/lib/client/browser');
const fetch = require('node-fetch');
const callServer = function(request, callback) {
const options = {
method: 'POST',
body: request,
headers: {
'Content-Type': 'application/json',
}
};
fetch('http://localhost:3000', options)
.then(function(res) { return res.text(); })
.then(function(text) { callback(null, text); })
.catch(function(err) { callback(err); });
};
const client = new jaysonBrowserClient(callServer, {
// other options go here
});
client.request('multiply', [5, 5], function(err, error, result) {
if(err) throw err;
console.log(result); // 25
});
Notification requests are for cases where the reply from the server is not important and should be ignored. This is accomplished by setting the id property of a request object to null.
Client example in examples/notifications/client.js doing a notification request:
const jayson = require('jayson');
const client = new jayson.client.http({
port: 3000
});
// the third parameter is set to "null" to indicate a notification
client.request('ping', [], null, function(err) {
if(err) throw err;
console.log('ok'); // request was received successfully
});
Server example in examples/notifications/server.js:
const jayson = require('jayson');
const server = new jayson.server({
ping: function(args, callback) {
// do something, do nothing
callback();
}
});
server.http().listen(3000);
null to Client.prototype.request does not generate a notification request. This argument has to be set explicitly to null for this to happen.null against the recommendation of the official specification. This behaviour can be overridden with the notificationIdNull option.A batch request is an array of individual requests that are sent to the server as one. Doing a batch request is very simple in Jayson and consists of constructing an array of individual requests (created by not passing a callback to Client.prototype.request) that is then itself passed to Client.prototype.request.
Combined server/client example in examples/batch_request/index.js:
const jayson = require('jayson');
const server = new jayson.server({
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
});
const client = new jayson.client(server);
const batch = [
client.request('does_not_exist', [10, 5]),
client.request('add', [1, 1]),
client.request('add', [0, 0], null) // a notification
];
client.request(batch, function(err, errors, successes) {
if(err) throw err;
console.log('errors', errors); // array of requests that errored
console.log('successes', successes); // array of requests that succeeded
});
client.request(batch, function(err, responses) {
if(err) throw err;
console.log('responses', responses); // all responses together
});
request. To find the right result, compare the ID from the request with the ID in the result yourself.When the length (number of arguments) of a client callback function is either 2 or 3 it receives slightly different values when invoked.
null, second argument is the response object as returned (containing either a result or a error property) or null for notifications.error property or null (if success), third argument is a JSON-RPC result property or null (if error).When doing a batch request with a 3-length callback, the second argument will be an array of requests with a error property and the third argument will be an array of requests with a result property.
A client will emit the following events (in addition to any special ones emitted by a specific interface):
| Event | When | Arguments | Notes |
|---|---|---|---|
request | About to dispatch a request | 1: Request object | |
response | Received a response | 1: Request object 2: Response object received |
The server classes are available as the Server or server property of require('jayson').
The server also sports several interfaces that can be accessed as properties of an instance of Server.
| Name | Description |
|---|---|
Server | Base interface for a server that supports receiving JSON-RPC requests |
Server.tcp | TCP server that inherits from net.Server |
Server.tls | TLS server that inherits from tls.Server |
Server.http | HTTP server that inherits from http.Server |
Server.https | HTTPS server that inherits from https.Server |
Server.middleware | Method that returns a Connect/Express compatible middleware function |
Servers supports these options:
| Option | Default | Type | Description |
|---|---|---|---|
reviver | null | Function | JSON.parse reviver |
replacer | null | Function | JSON.stringify replacer |
router | null | Function | Return the function for method routing |
useContext | false | Boolean | Passed to methodConstructor options |
params | undefined | Array/Object/null | Passed to methodConstructor options |
methodConstructor | jayson.Method | Function | Server functions are made an instance of this class |
version | 2 | Number | JSON-RPC version to support (1 or 2) |
Uses the same options as the base class. Inherits from net.Server.
Uses the same options as the base class. Inherits from tls.Server.
Uses the same options as the base class. Inherits from http.Server.
| Event | When | Arguments | Notes |
|---|---|---|---|
http request | Incoming HTTP request | 1. Instance of http.IncomingMessage | |
http response | About to send a HTTP response | 1. Instance of http.ServerResponse 2. Instance of http. IncomingMessage |
Uses the same options as the base class. Inherits from https.Server and jayson.Server.http. For information on how to configure certificates, see the documentation on https.Server.
Will emit the same custom events as Server.http.
Uses the same options as the base class. Returns a function that is compatible with Connect or Express. Will expect the request to be req.body, meaning that the request body must be parsed (typically using connect.bodyParser) before the middleware is invoked.
The middleware supports the following options:
| Option | Default | Type | Description |
|---|---|---|---|
end | true | Boolean | If set to false causes the middleware to next() instead of res.end() when finished. |
Middleware example in examples/middleware/server.js:
const jayson = require('jayson');
const jsonParser = require('body-parser').json;
const connect = require('connect');
const app = connect();
const server = new jayson.server({
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
});
// parse request body before the jayson middleware
app.use(jsonParser());
app.use(server.middleware());
app.listen(3000);
A Jayson server can use many interfaces at the same time.
Server example in examples/many_interfaces/server.js that listens to both http and a https requests:
const jayson = require('jayson');
const server = new jayson.server();
// "http" will be an instance of require('http').Server
const http = server.http();
// "https" will be an instance of require('https').Server
const https = server.https({
//cert: require('fs').readFileSync('cert.pem'),
//key require('fs').readFileSync('key.pem')
});
http.listen(80, function() {
console.log('Listening on *:80');
});
https.listen(443, function() {
console.log('Listening on *:443');
});
Passing an instance of a client as a method to the server makes the server relay incoming requests to wherever the client is pointing to. This might be used to delegate computationally expensive functions into a separate server or to abstract a cluster of servers behind a common interface.
Frontend server example in examples/relay/server_public.js listening on *:3000:
const jayson = require('jayson');
// create a server where "add" will relay a localhost-only server
const server = new jayson.server({
add: new jayson.client.http({
port: 3001
})
});
// let the frontend server listen to *:3000
server.http().listen(3000);
Backend server example in examples/relay/server_private.js listening on *:3001:
const jayson = require('jayson');
const server = new jayson.server({
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
});
// let the backend listen to *:3001
server.http().listen(3001);
Every request to add on the public server will now relay the request to the private server. See the client example in examples/relay/client.js.
Passing a property named router in the server options will enable you to write your own logic for routing requests to specific functions.
Server example with custom routing logic in examples/method_routing/server.js:
const jayson = require('jayson');
const methods = {
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
};
const server = new jayson.server(methods, {
router: function(method, params) {
// regular by-name routing first
if(typeof(this._methods[method]) === 'function') return this._methods[method];
if(method === 'add_2') {
const fn = server.getMethod('add').getHandler();
return new jayson.Method(function(args, done) {
args.unshift(2);
fn(args, done);
});
}
}
});
server.http().listen(3000);
Client example in examples/method_routing/client.js invoking add_2 on the above server:
const jayson = require('jayson');
// create a client
const client = new jayson.client.http({
port: 3000
});
// invoke "add_2"
client.request('add_2', [3], function(err, response) {
if(err) throw err;
console.log(response.result); // 5!
});
Server example of nested routes where each property is separated by a dot (you do not need to use the router option for this):
const _ = require('lodash');
const jayson = require('jayson');
const methods = {
foo: {
bar: function(callback) {
callback(null, 'ping pong');
}
},
math: {
add: function(args, callback) {
callback(null, args[0] + args[1]);
}
}
};
// this reduction produces an object like this: {'foo.bar': [Function], 'math.add': [Function]}
const map = _.reduce(methods, collapse('', '.'), {});
const server = new jayson.server(map);
function collapse(stem, sep) {
return function(map, value, key) {
const prop = stem ? stem + sep + key : key;
if(_.isFunction(value)) map[prop] = value;
else if(_.isObject(value)) map = _.reduce(value, collapse(prop, sep), map);
return map;
}
}
router does not return anything, the server will respond with a Method Not Found error.Server.prototype methods method, methods, removeMethod and hasMethod will not use the router method, but will operate on the internal Server.prototype._methods map.router method is expected to return instances of jayson.Method (>=1.2.0)You can also define server methods inside a wrapping object named jayson.Method. This allows additional options about the method to be specified. Using this wrapper - explicitly or implicitly (via server options) - makes it trivial to have your method accept a variable amount of arguments.
The method class is available as the Method or method property of require('jayson'). It supports these options:
| Option | Default | Type | Description |
|---|---|---|---|
handler | Function | The actual function that will handle a JSON-RPC request to this method | |
useContext | false | Boolean | When true, the handler will receive a context object as the second argument |
params | null | Array|Object|null | Force JSON-RPC parameters to be of a certain type |
Server example showcasing most features and options in examples/method_definitions/server.js:
const jayson = require('jayson');
const _ = require('lodash');
const methods = {
// this function will be wrapped in jayson.Method with options given to the server
sum: function(args, done) {
done(null, sum(args));
},
// this function always receives a context object as second arg
// it can be overriden on the server level
context: jayson.Method(function(args, context, done) {
done(null, context);
}, {useContext: true}),
// specifies some default values (alternate definition too)
sumDefault: jayson.Method(function(args, done) {
const total = sum(args);
done(null, total);
}, {
params: {a: 2, b: 5} // map of defaults
}),
// this method returns true when it gets an array (which it always does)
isArray: new jayson.Method({
handler: function(args, done) {
const result = _.isArray(args);
done(null, result);
},
params: Array // could also be "Object"
})
};
const server = new jayson.server(methods, {
// these options are given as options to jayson.Method when adding the method "sum".
// this is because it is not wrapped in jayson.Method like the others.
useContext: false,
params: Array
});
server.http().listen(3000);
// sums all numbers in an array or object
function sum(list) {
return _.reduce(list, function(sum, val) {
return sum + val;
}, 0);
}
Client example in examples/method_definitions/client.js:
const jayson = require('jayson');
const client = new jayson.client.http({
port: 3000
});
// invoke "sum" with array
client.request('sum', [3, 5, 9, 11], function(err, response) {
if(err) throw err;
console.log(response.result); // 28
});
// invoke "sum" with an object
client.request('sum', {a: 2, b: 3, c: 4}, function(err, response) {
if(err) throw err;
console.log(response.result); // 9
});
// invoke "sumDefault" with object missing some defined members
client.request('sumDefault', {b: 10}, function(err, response) {
if(err) throw err;
console.log(response.result); // 12
});
// invoke "isArray" with an Object
client.request('isArray', {a: 5, b: 2, c: 9}, function(err, response) {
if(err) throw err;
console.log(response.result); // true
});
// invoke "context"
client.request('context', {hello: 'world'}, function(err, response) {
if(err) throw err;
console.log(response.result); // {} - just an empty object
});
In addition to events that are specific to certain interfaces, all servers will emit the following events:
| Event | When | Arguments | Notes |
|---|---|---|---|
request | Interpretable non-batch request received | 1: Request object | |
response | Returning a response | 1: Request object 2: Response object | |
batch | Interpretable batch request received | 1. Array of requests | Emits request for every part |
If you should like to return an error from an method request to indicate a failure, remember that the JSON-RPC 2.0 specification requires the error to be an Object with a code (Integer/Number) to be regarded as valid. You can also provide a message (String) and a data (Object) with additional information. Example:
const jayson = require('jayson');
const server = new jayson.server({
i_cant_find_anything: function(args, callback) {
const error = {code: 404, message: 'Cannot find ' + args.id};
callback(error); // will return the error object as given
},
i_cant_return_a_valid_error: function(callback) {
callback({message: 'I forgot to enter a code'}); // will return a pre-defined "Internal Error"
}
});
It is also possible to cause a method to return one of the predefined JSON-RPC 2.0 error codes using the server helper function Server.prototype.error inside of a server method. Example:
const jayson = require('jayson');
const server = new jayson.server({
invalid_params: function(args, callback) {
const error = this.error(-32602); // returns an error with the default properties set
callback(error);
}
});
You can even override the default messages:
const jayson = require('jayson');
const server = new jayson.server({
error_giver_of_doom: function(callback) {
callback(true) // invalid error format, which causes an Internal Error to be returned instead
}
});
// Override the default message
server.errorMessages[Server.errors.INTERNAL_ERROR] = 'I has a sad. I cant do anything right';
Jayson does not include functionality for supporting CORS requests natively but it is easy to use a CORS-enabling middleware like cors. An example of this can be found in examples/cors/server.js:
const jayson = require('jayson');
const cors = require('cors');
const connect = require('connect');
const jsonParser = require('body-parser').json;
const app = connect();
const server = new jayson.server({
myNameIs: function(args, callback) {
callback(null, 'Your name is: ' + args.name);
}
});
app.use(cors({methods: ['POST']}));
app.use(jsonParser());
app.use(server.middleware());
app.listen(3000);
Since version 3.0.0
You can provide an optional context object to JSON-RPC method handlers. This can be used to give extra data to a handler such as request headers, authentication tokens, and so on.
This feature is unlocked by having jayson.Method accepts a boolean option called useContext. It always defaults to false for backwards compatibility. When it is set to true the method handler that jayson.Method wraps will always receive a context object as the second argument. The object can be given as the third argument to jayson.Server.prototype.call.
Server example in examples/context/server.js:
const _ = require('lodash');
const jayson = require('jayson');
const jsonParser = require('body-parser').json;
const express = require('express');
const app = express();
const server = new jayson.server({
getHeaders: function(args, context, callback) {
callback(null, context.headers);
},
// old method not receiving a context object (here for reference)
oldMethod: new jayson.Method(function(args, callback) {
callback(null, {});
}, {
// this setting overrides the server option set below for this particular method only
useContext: false
})
}, {
// all methods will receive a context object as the second arg
useContext: true
});
app.use(jsonParser());
app.use(function(req, res, next) {
// prepare a context object passed into the JSON-RPC method
const context = {headers: req.headers};
server.call(req.body, context, function(err, result) {
if(err) return next(err);
res.send(result || {});
});
});
app.listen(3001);
Client example in examples/context/client.js:
const jayson = require('jayson');
// create a client
const client = new jayson.client.http({
port: 3001
});
// invoke "getHeaders"
client.request('getHeaders', {}, function(err, response) {
if(err) throw err;
console.log(response.result);
});
jayson.Server also accepts useContext as an option, and passes the value on to the jayson.Method constructor. This option can be overriden on a per-method basis as shown above.jayson.Server.prototype.call, an empty object will be createdexpress http server. See the FAQ for more info about this.JSON lacks support for representing types other than the simple ones defined in the JSON specification. Fortunately the JSON methods in JavaScript (JSON.parse and JSON.stringify) provide options for custom serialization/deserialization routines. Jayson allows you to pass your own routines as options to both clients and servers.
Simple example transferring the state of an object between a client and a server:
Shared code between the server and the client in examples/reviving_and_replacing/shared.js:
'use strict';
const Counter = exports.Counter = function(value) {
this.count = value || 0;
};
Counter.prototype.increment = function() {
this.count += 1;
};
exports.replacer = function(key, value) {
if(value instanceof Counter) {
return {$class: 'counter', $props: {count: value.count}};
}
return value;
};
exports.reviver = function(key, value) {
if(value && value.$class === 'counter') {
const obj = new Counter();
for(const prop in value.$props) obj[prop] = value.$props[prop];
return obj;
}
return value;
};
Server example in examples/reviving_and_replacing/server.js:
const jayson = require('jayson');
const shared = require('./shared');
// Set the reviver/replacer options
const options = {
reviver: shared.reviver,
replacer: shared.replacer
};
// create a server
const server = new jayson.server({
increment: function(args, callback) {
args.counter.increment();
callback(null, args.counter);
}
}, options);
server.http().listen(3000);
A client example in examples/reviving_and_replacing/client.js invoking "increment" on the server:
const jayson = require('jayson');
const shared = require('./shared');
const client = new jayson.client.http({
port: 3000,
reviver: shared.reviver,
replacer: shared.replacer
});
// create the object
const params = {
counter: new shared.Counter(2)
};
// invoke "increment"
client.request('increment', params, function(err, response) {
if(err) throw err;
const result = response.result;
console.log(
result instanceof shared.Counter, // true
result.count, // 3
params.counter === result // false - result is a new object
);
});
toJSON method for any JavaScript object. Unfortunately there is no corresponding method for reviving objects (that would not work, obviously), so the reviver always has to be set up manually.It is possible to specify named parameters when doing a client request by passing an Object instead of an Array.
Client example in examples/named_parameters/client.js:
const jayson = require('jayson');
const client = new jayson.client.http({
port: 3000
});
client.request('add', {b: 1, a: 2}, function(err, response) {
if(err) throw err;
console.log(response.result); // 3!
});
Server example in examples/named_parameters/server.js:
const jayson = require('jayson');
const server = new jayson.server({
add: function(params, callback) {
callback(null, params.a + params.b);
}
});
server.http().listen(3000);
undefinedSince version 2.0.0
A separate tree that does limited usage of the ES6 Promise object is available. The internal API remains callback based, with the addition that promises may be used for two things:
To use the separate tree, do a require('jayson/promise') instead of require('jayson').
Server example in examples/promise/server.js showing how to return a Promise in a server method:
const jayson = require('jayson/promise');
const _ = require('lodash');
const server = new jayson.server({
add: async function(args) {
const sum = _.reduce(args, function(sum, value) { return sum + value; }, 0);
return sum;
},
// example on how to reject
rejection: async function(args) {
// server.error just returns {code: 501, message: 'not implemented'}
throw server.error(501, 'not implemented');
}
});
server.http().listen(3000);
Client example in examples/promise/client.js showing how to do a request:
const jayson = require('jayson/promise');
const client = new jayson.client.http({
port: 3000
});
const reqs = [
client.request('add', [1, 2, 3, 4, 5]),
client.request('rejection', [])
];
Promise.all(reqs).then(function(responses) {
console.log(responses[0].result);
console.log(responses[1].error);
});
Promise is considered to have been returned from a server method if the returned object has a property then that is a function.Since version 2.0.5
Sometimes you may want to return raw requests from a promise client. This needs to be handled differently, because PromiseClient.prototype.request would normally always be expected to return a Promise which we in this case don't want.
To solve this, we need to set the fourth parameter to PromiseClient.prototype.request explicitly to false in order to not return a Promise.
Client example in examples/promise_batches/client.js showing how to properly execute a batch request:
const jayson = require('jayson/promise');
const client = new jayson.client.http({
port: 3000
});
const batch = [
client.request('add', [1, 2, 3, 4, 5], undefined, false),
client.request('add', [5, 6, 7, 8, 9], undefined, false),
];
client.request(batch).then(function(responses) {
console.log(responses[0].result); // 15
console.log(responses[1].result); // 35
});
PromiseClient.prototype.request above is explicitly set to undefined - this parameter would normally represent the desired ID of the call. Remember that null would mean a notification (which does not return a response) and other falsy values may actually be used as ids. Setting undefined ensures that the id is generated automatically.A browser client that has no dependencies on node.js core libraries is available too. It works similar to how the regular callback-style Browser Client works. Here is an example:
'use strict';
const jaysonPromiseBrowserClient = require('jayson/promise/lib/client/browser');
const fetch = require('node-fetch');
const callServer = function(request) {
const options = {
method: 'POST',
body: request,
headers: {
'Content-Type': 'application/json',
}
};
return fetch('http://localhost:3000', options).then(res => res.text());
};
const client = new jaysonPromiseBrowserClient(callServer, {
// other options go here
});
client.request('multiply', [5, 5]).then(function(result) {
console.log(result);
}, function(err) {
console.error(err);
});
Please refer to the regular browser client section of the README for more information.
Support for method context added in version 3.0.0
See Server context section.
Using the provided clients and servers for http, https, tls, tcp and the express middleware is fine and works well for most use cases. However, sometimes issues like these crop up (quotes below are not directly from issue posters):
\r\n but the jayson client does not"These are not issues with jayson, but stem from the fact that JSON-RPC 2.0 specification is transport agnostic and these kind of behaviours are not defined by that specification. The clients provided by jayson for http, https, tls, tcp are made to work and tested with their corresponding jayson server implementation. Any other compatibility with any other server or client is accidental when it comes to details of the transport layer. With that said, jayson is made to be 100 % compatible with the JSON-RPC 2.0 specification and compatibility with other non-jayson servers or clients when it comes to the application layer is pretty much guaranteed.
The library author tedeh therefore recommends that if you have particular needs when it comes to the transport layer you create an implementation satisfying these details yourself. Doing this is actually quite simple.
Example of a http server built with express in examples/faq_recommended_http_server/server.js:
const _ = require('lodash');
const jayson = require('jayson');
const jsonParser = require('body-parser').json;
const express = require('express');
const app = express();
// create a plain jayson server
const server = new jayson.server({
add: function(numbers, callback) {
callback(null, _.reduce(numbers, (sum, val) => sum + val, 0));
}
});
app.use(jsonParser()); // <- here we can deal with maximum body sizes, etc
app.use(function(req, res, next) {
const request = req.body;
// <- here we can check headers, modify the request, do logging, etc
server.call(request, function(err, response) {
if(err) {
// if err is an Error, err is NOT a json-rpc error
if(err instanceof Error) return next(err);
// <- deal with json-rpc errors here, typically caused by the user
res.status(400);
res.send(err);
return;
}
// <- here we can mutate the response, set response headers, etc
if(response) {
res.send(response);
} else {
// empty response (could be a notification)
res.status(204);
res.send('');
}
});
});
app.listen(3001);
Using some of the utilities provided and exported by jayson, creating a client offering the same kind of flexibility is also simple. Example of a compatible http client built with superagent in examples/faq_recommended_http_server/client.js:
const jayson = require('jayson');
const request = require('superagent');
// generate a json-rpc version 2 compatible request (non-notification)
const requestBody = jayson.Utils.request('add', [1,2,3,4], undefined, {
version: 2, // generate a version 2 request
});
request.post('http://localhost:3001')
// <- here we can setup timeouts, set headers, cookies, etc
.timeout({response: 5000, deadline: 60000})
.send(requestBody)
.end(function(err, response) {
if(err) {
// superagent considers 300-499 status codes to be errors
// @see http://visionmedia.github.io/superagent/#error-handling
if(!err.status) throw err;
const body = err.response.body;
// body may be a JSON-RPC error, or something completely different
// it can be handled here
if(body && body.error && jayson.Utils.Response.isValidError(body.error, 2)) {
// the error body was a valid JSON-RPC version 2
// we may wish to deal with it differently
console.err(body.error);
return;
}
throw err; // error was something completely different
}
const body = response.body;
// check if we got a valid JSON-RPC 2.0 response
if(!jayson.Utils.Response.isValidResponse(body, 2)) {
console.err(body);
}
if(body.error) {
// we have a json-rpc error...
console.err(body.error); // 10!
} else {
// do something useful with the result
console.log(body.result); // 10!
}
});
Highlighting issues or submitting pull requests on Github is most welcome.
Please make sure to follow the style of the project, and lint your code with npm run lint before submitting a patch.
You are required to provide an easily reproducible code sample of any errors with the Typescript type definitions so that they can be added to the typescript test file in typescript/test.ts. Better yet, issue a pull request adding a test there yourself that shows up when running the package.json script test-tsc.
FAQs
JSON-RPC 1.0/2.0 compliant server and client
We found that jayson demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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