关于javascript:Theia-技术揭秘之-JSONRPC-通信

实现了双向通信的对立接口，比照 cyrus-and/chrome-remote-interface 应用协定定义文件主动生成 Chrome Debugging Protocol 接口，两种实现形式，各有千秋。
还能够参考 VSCode 的 Language server protocol Node 实现 microsoft/vscode-languageserver-node，外面蕴含了 RPC 的 IPC 版本 vscode-jsonrpc
Theia 的 WebSocket 连贯基于 RPC 的 WS 版本 vscode-ws-jsonrpc
JSON 标准方面，能够和 Chrome DevTools Protocol 的以及 VSCode 的 Language Server Protocol Specification 的标准对照着看，能够查看 JSON RPC 官网标准
搞清楚 JsonRpcServer，ConnectionHandler，JsonRpcConnectionHandler 的作用和关系
查看示例源码：Add debug logging support · eclipse-theia/theia@99d191f

Theia 框架前端 UI 布局和 Services 一样，具备灵便可拓展的特点。VSCode 是内置了一套根本的组件零碎，而 Theia 框架的 UI 布局基于 PhosphorJS 框架。PhosphorJS 提供了蕴含 widgets、layouts、事件和数据结构的丰盛工具包。这使得开发人员可能构建可扩大的、高性能的、类桌面的 Web 应用程序，比方 JupyterLab。

PhosphorJS 作者退休，我的项目已归档，该我的项目当初被 Jupyter 团队重命名为 jupyterlab/lumino 持续保护。见 issue：https://github.com/jupyterlab…

前置条件：

理解 Theia 的简略原理及前后端模块加载的形式
理解 InversifyJS 的依赖注入的原理和应用

Theia JSON RPC 实现的毛病：

概念多，什么 factory，proxy 等，server 和 client 概念有点混同。
每次增加接口都须要实现 IServer/IClient/IWatcher，而后依照标准注入，工作量并不少
和 Inversify、Theia 源码、后端服务耦合重大，没有独立成包

在启动后，Theia 会启动一个 Express 服务。前后端的 JSON-RPC 通信，正是基于 Express 上的 Websocket 连贯。

接下来将创立调试日志零碎服务，而后通过 JSON RPC 连贯到它。

因而，你要做的第一件事是裸露服务，以便前端能够连贯到它。

你须要创立相似于上面这个 (logger-server-module. ts) 的后端服务器模块文件:

import {ContainerModule} from 'inversify';
import {ConnectionHandler, JsonRpcConnectionHandler} from "../../messaging/common";
import {ILoggerServer, ILoggerClient} from '../../application/common/logger-protocol';

export const loggerServerModule = new ContainerModule(bind => {bind(ConnectionHandler).toDynamicValue(ctx =>
        new JsonRpcConnectionHandler<ILoggerClient>("/services/logger", client => {const loggerServer = ctx.container.get<ILoggerServer>(ILoggerServer);
            loggerServer.setClient(client);
            return loggerServer;
        })
    ).inSingletonScope()});

外围在于 ConnectionHandler 和 JsonRpcConnectionHandler。

ConnectionHandler：是一个简略的接口，它指定连贯的 path 以及 onConnection 办法。
JsonRpcConnectionHandler：这个工厂容许您创立一个连贯处理程序，onConnection 创立代理对象到 JSON-RPC 的后端调用的对象，并将本地对象裸露给 JSON-RPC。
ILoggerServer：定义通过 JSON-RPC 调用的后端对象。
ILoggerClient：是一个 Client 对象，定义来自后端对象的告诉的接管。

ConnectionHandler 类型绑定到 messaging-module.ts 中的 ContributionProvider。

当 MessagingContribution 启动（调用 onStart）时，它为所有绑定 ConnectionHandlers 创立一个 Websocket 连贯。

即顺次在 Server 注册 path，并绑定 onConnection 事件。

// packages/core/src/node/messaging/messaging-contribution.ts
export class MessagingContribution implements BackendApplicationContribution, MessagingService {constructor( @inject(ContributionProvider) @named(ConnectionHandler) protected readonly handlers: 
  ContributionProvider<ConnectionHandler>) { }

    // 服务启动时调用
    onStart(server: http.Server): void {
        // 遍历
        for (const handler of this.handlers.getContributions()) {
            const path = handler.path;
            try {
                createServerWebSocketConnection({
                    server,
                    path
                }, connection => handler.onConnection(connection));
            } catch (error) {console.error(error)
            }
        }
    }
}

咱们看看一下 JsonRpcConnectionHandler 的实现，就会发现 onConnection 做了三件事：

基于 JsonRpcProxyFactory 和传入的 path 创立 factory 实例
通过 createProxy 办法创立代理 proxy
从 factory 创立一个代理对象：factory.target = this.targetFactory(proxy);
将 factory 和 connection 连接起来

第三步将调用 new JsonRpcConnectionHandler() 传入的函数：

        client => {const loggerServer = ctx.container.get<ILoggerServer>(ILoggerServer);
            loggerServer.setClient(client);
            return loggerServer;
        }

这将在 loggerServer 上设置 Client，在这种状况下，用于向前端发送 onLogLevelChanged 告诉。

// packages/core/src/common/messaging/proxy-factory.ts
export class JsonRpcConnectionHandler<T extends object> implements ConnectionHandler {
    constructor(
        readonly path: string,
        readonly targetFactory: (proxy: JsonRpcProxy<T>) => any,
        readonly factoryConstructor: new () => JsonRpcProxyFactory<T> = JsonRpcProxyFactory) { }
        onConnection(connection: MessageConnection): void {
            // 1. 在 path“logger”上创立了一个 JsonRpcProxy
            const factory = new JsonRpcProxyFactory(this.path);
            
            // 2. 在 factory 类上创立了一个代理对象
            // 这个对象能够应用 ILoggerClient 定义的接口调用 JSON-RPC 的另一端。const proxy = factory.createProxy();
            
            // 3. 这里调用了 new JsonRpcConnectionHandler 传入的函数 client=>{}，用于 loggerServer.setClient
            factory.target = this.targetFactory(proxy);
        
          // 4. 这将 factory 与 connection 连贯了起来
            factory.listen(connection);
        }
    }
}

这样，services/* 的申请由 Webpack dev server 解决，请参阅 webpack.config.js。

'/services/*': {
    target: 'ws://localhost:3000',
    ws: true
},

Server 定义通过 JSON-RPC 调用的后端对象，ILoggerServer 接口如下，这里定义了 4 个办法。

// packages/core/src/common/logger-protocol.ts
export interface ILoggerServer extends JsonRpcServer<ILoggerClient> {setLogLevel(name: string, logLevel: number): Promise<void>;
    getLogLevel(name: string): Promise<number>;
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    log(name: string, logLevel: number, message: any, params: any[]): Promise<void>;
    child(name: string): Promise<void>;
}

继承自 JsonRpcServer：

// packages/core/src/common/messaging/proxy-factory.ts
export type JsonRpcServer<Client> = Disposable & {
    /**
     * If this server is a proxy to a remote server then
     * a client is used as a local object
     * to handle JSON-RPC messages from the remote server.
     */
    setClient(client: Client | undefined): void;
    getClient?(): Client | undefined;};

以后，源码中仅有 ConsoleLoggerServer 的实现：export class ConsoleLoggerServer implements ILoggerServer {}

Client 用于定义接管来自后端对象的告诉，DispatchingLoggerClient 实现如下：

// packages/core/src/common/logger-protocol.ts
@injectable()
export class DispatchingLoggerClient implements ILoggerClient {readonly clients = new Set<ILoggerClient>();

    onLogLevelChanged(event: ILogLevelChangedEvent): void {this.clients.forEach(client => client.onLogLevelChanged(event));
    }

}

下面咱们创立了后端服务，接下来咱们须要从前端连贯它。

分为以下三步：

创立了一个 watcher，应用 loggerWatcher Client 从后端获取事件告诉
取得了 Websocket 连贯
通过 loggerWatcher.getLoggerClient() 取得本地对象，用来来解决来自近程对象的 JSON-RPC 音讯，通过传入 createProxy 创立一个代理

// logger-frontend-module. ts
import {ContainerModule, Container} from 'inversify';
import {WebSocketConnectionProvider} from '../../messaging/browser/connection';
import {ILogger, LoggerFactory, LoggerOptions, Logger} from '../common/logger';
import {ILoggerServer} from '../common/logger-protocol';
import {LoggerWatcher} from '../common/logger-watcher';

export const loggerFrontendModule = new ContainerModule(bind => {bind(ILogger).to(Logger).inSingletonScope();
          // 1. 这里创立了一个 watcher，应用 loggerWatcher Client 从后端获取事件告诉
    bind(LoggerWatcher).toSelf().inSingletonScope();
    bind(ILoggerServer).toDynamicValue(ctx => {const loggerWatcher = ctx.container.get(LoggerWatcher);
    // 2. 这里取得了一个 Websocket 连贯
        const connection = ctx.container.get(WebSocketConnectionProvider);
        // 3. 这里，咱们传入了一个用于解决 JSON-RPC 的对象。return connection.createProxy<ILoggerServer>("/services/logger", loggerWatcher.getLoggerClient());
    }).inSingletonScope();});

WebSocketConnectionProvider 的 connection.createProxy 理论执行以下代码：

// packages/core/src/common/messaging/abstract-connection-provider.ts
export abstract class AbstractConnectionProvider<AbstractOptions extends object> {
    /**
     * Create a proxy object to remote interface of T type
     * over a web socket connection for the given path.
     */
    createProxy<T extends object>(path: string, arg?: object): JsonRpcProxy<T> {const factory = arg instanceof JsonRpcProxyFactory ? arg : new JsonRpcProxyFactory<T>(arg);
        this.listen({
            path,
            onConnection: c => factory.listen(c)
        });
        return factory.createProxy();}
    /**
     * Install a connection handler for the given path.
     */
    listen(handler: ConnectionHandler, options?: AbstractOptions): void {
        this.openChannel(handler.path, channel => {const connection = createWebSocketConnection(channel, this.createLogger());
            connection.onDispose(() => channel.close());
            handler.onConnection(connection);
        }, options);
    }
}

接下来，即可应用 ILoggerService 获取对象进行 RPC 调用。

LoggerWatcher 定义了 onLogLevelChanged 的音讯响应。

@injectable()
export class LoggerWatcher {getLoggerClient(): ILoggerClient {
        const emitter = this.onLogLevelChangedEmitter;
        return {onLogLevelChanged(event: ILogLevelChangedEvent): void {emitter.fire(event);
            }
        };
    }

    private onLogLevelChangedEmitter = new Emitter<ILogLevelChangedEvent>();

    get onLogLevelChanged(): Event<ILogLevelChangedEvent> {return this.onLogLevelChangedEmitter.event;}

    // FIXME: get rid of it, backend services should as well set a client on the server
    fireLogLevelChanged(event: ILogLevelChangedEvent): void {this.onLogLevelChangedEmitter.fire(event);
    }
}

须要导入模块和加载进主容器两步。

// 导入模块
import {loggerServerModule} from 'theia-core/lib/application/node/logger-server-module';

// 加载进容器
container.load(loggerServerModule);

残缺的通信例子能够看：

Add debug logging support · eclipse-theia/theia@99d191f

外围的接口和类有：ConnectionHandler，JsonRpcConnectionHandler 以及 JsonRpcProxyFactory，搞清楚他们的作用。

ConnectionHandler 是一个简略的接口，它指定连贯的 path 以及 onConnection 办法。

export interface ConnectionHandler {
    readonly path: string;
    onConnection(connection: MessageConnection): void;
}

JsonRpcProxyFactory 在 JsonRpcConnectionHandler 中被应用。

Websocket 连贯正是在 JsonRpcConnectionHandler 类上建设的。建设连贯的逻辑在 JsonRpcConnectionHandler 类的 onConnection 函数上，过程如下：

// packages/core/src/common/messaging/proxy-factory.ts
export class JsonRpcConnectionHandler<T extends object> implements ConnectionHandler {
    constructor(
        readonly path: string,
        readonly targetFactory: (proxy: JsonRpcProxy<T>) => any,
        readonly factoryConstructor: new () => JsonRpcProxyFactory<T> = JsonRpcProxyFactory) { }
        onConnection(connection: MessageConnection): void {
            // 在 path“logger”上创立了一个 JsonRpcProxy
            const factory = new JsonRpcProxyFactory(this.path);
            
            // 在 factory 类上创立了一个代理对象
            // 这个对象能够应用 ILoggerClient 定义的接口调用 JSON-RPC 的另一端。const proxy = factory.createProxy();
            
            // 这里调用了咱们在参数中传入的函数
            factory.target = this.targetFactory(proxy);
        
          // 这将 factory 与 connection 连贯了起来
            factory.listen(connection);
        }
    }
}

JSON RPC 的外围在于：JsonRpcProxyFactory，源码里正文很具体，还有应用 Demo，值得好好学习一下。

// packages/core/src/common/messaging/proxy-factory.ts
/**
 * Factory for JSON-RPC proxy objects.
 *
 * A JSON-RPC proxy exposes the programmatic interface of an object through
 * JSON-RPC.  This allows remote programs to call methods of this objects by
 * sending JSON-RPC requests.  This takes place over a bi-directional stream,
 * where both ends can expose an object and both can call methods each other's
 * exposed object.
 *
 * For example, assuming we have an object of the following type on one end:
 *
 *     class Foo {*         bar(baz: number): number {return baz + 1}
 *     }
 *
 * which we want to expose through a JSON-RPC interface.  We would do:
 *
 *     let target = new Foo()
 *     let factory = new JsonRpcProxyFactory<Foo>('/foo', target)
 *     factory.onConnection(connection)
 *
 * The party at the other end of the `connection`, in order to remotely call
 * methods on this object would do:
 *
 *     let factory = new JsonRpcProxyFactory<Foo>('/foo')
 *     factory.onConnection(connection)
 *     let proxy = factory.createProxy();
 *     let result = proxy.bar(42)
 *     // result is equal to 43
 *
 * One the wire, it would look like this:
 *
 *     --> {"jsonrpc": "2.0", "id": 0, "method": "bar", "params": {"baz": 42}}
 *     <-- {"jsonrpc": "2.0", "id": 0, "result": 43}
 *
 * Note that in the code of the caller, we didn't pass a target object to
 * JsonRpcProxyFactory, because we don't want/need to expose an object.
 * If we had passed a target object, the other side could've called methods on
 * it.
 *
 * @param <T> - The type of the object to expose to JSON-RPC.
 */
export class JsonRpcProxyFactory<T extends object> implements ProxyHandler<T> {protected readonly onDidOpenConnectionEmitter = new Emitter<void>();
    protected readonly onDidCloseConnectionEmitter = new Emitter<void>();

    protected connectionPromiseResolve: (connection: MessageConnection) => void;
    protected connectionPromise: Promise<MessageConnection>;

    /**
     * Build a new JsonRpcProxyFactory.
     *
     * @param target - The object to expose to JSON-RPC methods calls.  If this
     *   is omitted, the proxy won't be able to handle requests, only send them.
     */
    constructor(public target?: any) {this.waitForConnection();
    }

    protected waitForConnection(): void {
        this.connectionPromise = new Promise(resolve =>
            this.connectionPromiseResolve = resolve
        );
        this.connectionPromise.then(connection => {connection.onClose(() =>
                this.onDidCloseConnectionEmitter.fire(undefined)
            );
            this.onDidOpenConnectionEmitter.fire(undefined);
        });
    }

    /**
     * Connect a MessageConnection to the factory.
     *
     * This connection will be used to send/receive JSON-RPC requests and
     * response.
     */
    listen(connection: MessageConnection): void {if (this.target) {for (const prop in this.target) {if (typeof this.target[prop] === 'function') {connection.onRequest(prop, (...args) => this.onRequest(prop, ...args));
                    connection.onNotification(prop, (...args) => this.onNotification(prop, ...args));
                }
            }
        }
        connection.onDispose(() => this.waitForConnection());
        connection.listen();
        this.connectionPromiseResolve(connection);
    }

    /**
     * Process an incoming JSON-RPC method call.
     *
     * onRequest is called when the JSON-RPC connection received a method call
     * request.  It calls the corresponding method on [[target]].
     *
     * The return value is a Promise object that is resolved with the return
     * value of the method call, if it is successful.  The promise is rejected
     * if the called method does not exist or if it throws.
     *
     * @returns A promise of the method call completion.
     */
    protected async onRequest(method: string, ...args: any[]): Promise<any> {
        try {return await this.target[method](...args);
        } catch (error) {const e = this.serializeError(error);
            if (e instanceof ResponseError) {throw e;}
            const reason = e.message || '';
            const stack = e.stack || '';
            console.error(`Request ${method} failed with error: ${reason}`, stack);
            throw e;
        }
    }

    /**
     * Process an incoming JSON-RPC notification.
     *
     * Same as [[onRequest]], but called on incoming notifications rather than
     * methods calls.
     */
    protected onNotification(method: string, ...args: any[]): void {this.target[method](...args);
    }

    /**
     * Create a Proxy exposing the interface of an object of type T.  This Proxy
     * can be used to do JSON-RPC method calls on the remote target object as
     * if it was local.
     *
     * If `T` implements `JsonRpcServer` then a client is used as a target object for a remote target object.
     */
    createProxy(): JsonRpcProxy<T> {const result = new Proxy<T>(this as any, this);
        return result as any;
    }

    /**
     * Get a callable object that executes a JSON-RPC method call.
     *
     * Getting a property on the Proxy object returns a callable that, when
     * called, executes a JSON-RPC call.  The name of the property defines the
     * method to be called.  The callable takes a variable number of arguments,
     * which are passed in the JSON-RPC method call.
     *
     * For example, if you have a Proxy object:
     *
     *     let fooProxyFactory = JsonRpcProxyFactory<Foo>('/foo')
     *     let fooProxy = fooProxyFactory.createProxy()
     *
     * accessing `fooProxy.bar` will return a callable that, when called,
     * executes a JSON-RPC method call to method `bar`.  Therefore, doing
     * `fooProxy.bar()` will call the `bar` method on the remote Foo object.
     *
     * @param target - unused.
     * @param p - The property accessed on the Proxy object.
     * @param receiver - unused.
     * @returns A callable that executes the JSON-RPC call.
     */
    get(target: T, p: PropertyKey, receiver: any): any {if (p === 'setClient') {return (client: any) => {this.target = client;};
        }
        if (p === 'getClient') {return () => this.target;
        }
        if (p === 'onDidOpenConnection') {return this.onDidOpenConnectionEmitter.event;}
        if (p === 'onDidCloseConnection') {return this.onDidCloseConnectionEmitter.event;}
        const isNotify = this.isNotification(p);
        return (...args: any[]) => {const method = p.toString();
            const capturedError = new Error(`Request '${method}' failed`);
            return this.connectionPromise.then(connection =>
                new Promise((resolve, reject) => {
                    try {if (isNotify) {  
                            // sendNotification
                            connection.sendNotification(method, ...args);
                            resolve();} else {
                            // sendRequest
                            const resultPromise = connection.sendRequest(method, ...args) as Promise<any>;
                            resultPromise
                                .catch((err: any) => reject(this.deserializeError(capturedError, err)))
                                .then((result: any) => resolve(result));
                        }
                    } catch (err) {reject(err);
                    }
                })
            );
        };
    }

    /**
     * Return whether the given property represents a notification.
     *
     * A property leads to a notification rather than a method call if its name
     * begins with `notify` or `on`.
     *
     * @param p - The property being called on the proxy.
     * @return Whether `p` represents a notification.
     */
    protected isNotification(p: PropertyKey): boolean {return p.toString().startsWith('notify') || p.toString().startsWith('on');
    }

    protected serializeError(e: any): any {if (ApplicationError.is(e)) {
            return new ResponseError(e.code, '',
                Object.assign({kind: 'application'}, e.toJson())
            );
        }
        return e;
    }
    protected deserializeError(capturedError: Error, e: any): any {if (e instanceof ResponseError) {
            const capturedStack = capturedError.stack || '';
            if (e.data && e.data.kind === 'application') {const { stack, data, message} = e.data;
                return ApplicationError.fromJson(e.code, {
                    message: message || capturedError.message,
                    data,
                    stack: `${capturedStack}\nCaused by: ${stack}`
                });
            }
            e.stack = capturedStack;
        }
        return e;
    }

}

集体还是感觉 cyrus-and/chrome-remote-interface 应用协定定义文件主动生成形式更优雅，代码更简洁。且独立成包，每次只须要增加 protocol 类型文件内容即可主动生成接口。

不过 chrome-remote-interface 只是一个客户端接口，并没有服务端。集体参考着设计了基于 Websocket 的 JSON RPC 协定标准和及 API。：cloudbase-interface，具备以下长处：

蕴含服务端和客户端
不论后端应用什么 websocket 框架，只须要提供：serverAdaptor 接口的实现即可。
应用中间件的思维裁减 API

Communication via JSON-RPC
JSON-RPC 2.0 Specification
microsoft/vscode-languageserver-node

关于javascript:Theia-技术揭秘之-JSONRPC-通信

写在后面

Theia JSON-RPC 协定示例

增加日志调试 JSON RPC 服务

注册服务

ConnectionHandler

JsonRpcConnectionHandler

Server 实现

Client 实现

前端连贯服务

LoggerWatcher

加载模块

源码

ConnectionHandler

JsonRpcConnectionHandler

JsonRpcProxyFactory

写在最初

参考