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Unified Diff: pkg/json_rpc_2/lib/src/server.dart

Issue 205533005: Create a package that implements a JSON-RPC 2.0 server. (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: code review Created 6 years, 9 months ago
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Index: pkg/json_rpc_2/lib/src/server.dart
diff --git a/pkg/json_rpc_2/lib/src/server.dart b/pkg/json_rpc_2/lib/src/server.dart
new file mode 100644
index 0000000000000000000000000000000000000000..d05c54f9ee85a82ae89d3c79174820727787987c
--- /dev/null
+++ b/pkg/json_rpc_2/lib/src/server.dart
@@ -0,0 +1,220 @@
+// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library json_rpc_2.server;
+
+import 'dart:async';
+import 'dart:collection';
+import 'dart:convert';
+
+import 'package:stack_trace/stack_trace.dart';
+
+import '../error_code.dart' as error_code;
+import 'exception.dart';
+import 'parameters.dart';
+import 'utils.dart';
+
+/// A JSON-RPC 2.0 server.
+///
+/// A server exposes methods that are called by requests, to which it provides
+/// responses. Methods can be registered using [registerMethod] and
+/// [registerFallback]. Requests can be handled using [handleRequest] and
+/// [parseRequest].
+///
+/// Note that since requests can arrive asynchronously and methods can run
+/// asynchronously, it's possible for multiple methods to be invoked at the same
+/// time, or even for a single method to be invoked multiple times at once.
+class Server {
+ /// The methods registered for this server.
+ final _methods = new Map<String, Function>();
+
+ /// The fallback methods for this server.
+ ///
+ /// These are tried in order until one of them doesn't throw a
+ /// [RpcException.methodNotFound] exception.
+ final _fallbacks = new Queue<Function>();
+
+ Server();
+
+ /// Registers a method named [name] on this server.
+ ///
+ /// [callback] can take either zero or one arguments. If it takes zero, any
+ /// requests for that method that include parameters will be rejected. If it
+ /// takes one, it will be passed a [Parameters] object.
+ ///
+ /// [callback] can return either a JSON-serializable object or a Future that
+ /// completes to a JSON-serializable object. Any errors in [callback] will be
+ /// reported to the client as JSON-RPC 2.0 errors.
+ void registerMethod(String name, Function callback) {
+ if (_methods.containsKey(name)) {
+ throw new ArgumentError('There\'s already a method named "$name".');
+ }
+
+ _methods[name] = callback;
+ }
+
+ /// Registers a fallback method on this server.
+ ///
+ /// A server may have any number of fallback methods. When a request comes in
+ /// that doesn't match any named methods, each fallback is tried in order. A
+ /// fallback can pass on handling a request by throwing a
+ /// [RpcException.methodNotFound] exception.
+ ///
+ /// [callback] can return either a JSON-serializable object or a Future that
+ /// completes to a JSON-serializable object. Any errors in [callback] will be
+ /// reported to the client as JSON-RPC 2.0 errors. [callback] may send custom
+ /// errors by throwing an [RpcException].
+ void registerFallback(callback(Parameters parameters)) {
+ _fallbacks.add(callback);
+ }
+
+ /// Handle a request that's already been parsed from JSON.
+ ///
+ /// [request] is expected to be a JSON-serializable object representing a
+ /// request sent by a client. This calls the appropriate method or methods for
+ /// handling that request and returns a JSON-serializable response, or `null`
+ /// if no response should be sent. [callback] may send custom
+ /// errors by throwing an [RpcException].
+ Future handleRequest(request) {
+ return syncFuture(() {
+ if (request is! List) return _handleSingleRequest(request);
+ if (request.isEmpty) {
+ return new RpcException(error_code.INVALID_REQUEST, 'A batch must '
+ 'contain at least one request.').serialize(request);
+ }
+
+ return Future.wait(request.map(_handleSingleRequest)).then((results) {
+ var nonNull = results.where((result) => result != null);
+ return nonNull.isEmpty ? null : nonNull.toList();
+ });
+ });
+ }
+
+ /// Parses and handles a JSON serialized request.
+ ///
+ /// This calls the appropriate method or methods for handling that request and
+ /// returns a JSON string, or `null` if no response should be sent.
+ Future<String> parseRequest(String request) {
+ return syncFuture(() {
+ var decodedRequest;
+ try {
+ decodedRequest = JSON.decode(request);
+ } on FormatException catch (error) {
+ return new RpcException(error_code.PARSE_ERROR, 'Invalid JSON: '
+ '${error.message}').serialize(request);
+ }
+
+ return handleRequest(decodedRequest);
+ }).then((response) {
+ if (response == null) return null;
+ return JSON.encode(response);
+ });
+ }
+
+ /// Handles an individual parsed request.
+ Future _handleSingleRequest(request) {
+ return syncFuture(() {
+ _validateRequest(request);
+
+ var name = request['method'];
+ var method = _methods[name];
+ if (method == null) method = _tryFallbacks;
+
+ if (method is ZeroArgumentFunction) {
+ if (!request.containsKey('params')) return method();
+ throw new RpcException.invalidParams('No parameters are allowed for '
+ 'method "$name".');
+ }
+
+ return method(new Parameters(name, request['params']));
+ }).then((result) {
+ // A request without an id is a notification, which should not be sent a
+ // response, even if one is generated on the server.
+ if (!request.containsKey('id')) return null;
+
+ return {
+ 'jsonrpc': '2.0',
+ 'result': result,
+ 'id': request['id']
+ };
+ }).catchError((error, stackTrace) {
+ if (error is! RpcException) {
+ error = new RpcException(
+ error_code.SERVER_ERROR, getErrorMessage(error), data: {
+ 'full': error.toString(),
+ 'stack': new Chain.forTrace(stackTrace).toString()
+ });
+ }
+
+ if (error.code != error_code.INVALID_REQUEST &&
+ !request.containsKey('id')) {
+ return null;
+ } else {
+ return error.serialize(request);
+ }
+ });
+ }
+
+ /// Validates that [request] matches the JSON-RPC spec.
+ void _validateRequest(request) {
+ if (request is! Map) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request must be '
+ 'an Array or an Object.');
+ }
+
+ if (!request.containsKey('jsonrpc')) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request must '
+ 'contain a "jsonrpc" key.');
+ }
+
+ if (request['jsonrpc'] != '2.0') {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Invalid JSON-RPC '
+ 'version ${JSON.encode(request['jsonrpc'])}, expected "2.0".');
+ }
+
+ if (!request.containsKey('method')) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request must '
+ 'contain a "method" key.');
+ }
+
+ var method = request['method'];
+ if (request['method'] is! String) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request method must '
+ 'be a string, but was ${JSON.encode(method)}.');
+ }
+
+ var params = request['params'];
+ if (request.containsKey('params') && params is! List && params is! Map) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request params must '
+ 'be an Array or an Object, but was ${JSON.encode(params)}.');
+ }
+
+ var id = request['id'];
+ if (id != null && id is! String && id is! num) {
+ throw new RpcException(error_code.INVALID_REQUEST, 'Request id must be a '
+ 'string, number, or null, but was ${JSON.encode(id)}.');
+ }
+ }
+
+ /// Try all the fallback methods in order.
+ Future _tryFallbacks(Parameters params) {
+ var iterator = _fallbacks.toList().iterator;
+
+ _tryNext() {
+ if (!iterator.moveNext()) {
+ return new Future.error(
+ new RpcException.methodNotFound(params.method),
+ new Chain.current());
+ }
+
+ return syncFuture(() => iterator.current(params)).catchError((error) {
+ if (error is! RpcException) throw error;
+ if (error.code != error_code.METHOD_NOT_FOUND) throw error;
+ return _tryNext();
+ });
+ }
+
+ return _tryNext();
+ }
+}
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