如何使用Connector架构完成设备接入_物联网边缘计算(IoT Edge)-阿里云帮助中心

本文档介绍驱动（设备接入模块）的Connector架构模式。Connector是一种结构清晰又灵活的模式，方便您快速构建驱动。我们推荐您使用Connector架构模式构建驱动程序。

Connector架构模式目前只适用于Node.js和Python的设备接入SDK。

概述

Connector模式架构图如下：

在Connector架构模式中，驱动程序由4个部分组成：

ThingAccessClient
此类由设备接入SDK提供，提供多个方法与Link IoT Edge交互，包括数据上行和数据下行。同时接受外部传入ThingAccessClientCallbacks类型回调函数，在收到Link IoT Edge的下行数据时调用回调接口。Connector架构中ThingAccessClientCallbacks的实现类是Connector类。
Connector
Connector架构核心组件。对外，Connector组件提供connect和disconnect接口，并接受外部注入Thing接口。对内，Connector组件实现ThingAccessClientCallbacks接口，并在构建ThingAccessClient对象时传入，以建立与Link IoT Edge的连接，并在收到回调指令时转发指令到设备。
Thing
对物理设备接口提供封装，负责与设备交互，方便Connector组件调用，对外提供面向对象的API。Thing在这里只是一个统称，接入具体设备时为具体设备抽象类，如Light（表示灯设备）。
Entry
驱动程序主入口，将会获取驱动配置，初始Thing组件和Connector组件，最终调用Connector组件的connect方法连接设备和Link IoT Edge。也可调用disconnect方法断开设备与Link IoT Edge的连接。

Connector组件是Connector架构中最重要的组件，它通过组合的方式将设备抽象接口（Thing）和Link IoT Edge抽象接口（ThingAccessClient）关联起来，因此而得名Connector。

UML类图如下所示：

操作步骤

下文示例使用Node.js版本设备接入SDK实现Connector架构模式。关于Python版本示例及详细信息可参考Python版本。

Light

本示例演示一个模拟灯的驱动程序设计。

抽象模拟灯类。通过设置isOn属性的true和false来标识模拟灯的开和关。

示例代码如下：

/**
 * A virtual light which can be turned on or off by updating its
 * <code>isOn</code> property.
 */
class Light {
  constructor() {
    this._isOn = true;
  }

  get isOn() {
    return this._isOn;
  }

  set isOn(value) {
    return this._isOn = value;
  }

实现Connector。代码主要包含如下功能：

构造函数接收设备的配置参数和设备抽象对象，内部构造ThingAccessClient以便与Link IoT Edge交互。
实现ThingAccessClientCallbacks的3个回调方法，并在回调方法中调用设备对象接口与设备交互。
提供connect方法和disconnect方法。其中在connect方法里连接Link IoT Edge，在disconnect方法里断开设备与Link IoT Edge的连接。

示例代码如下：

/**
 * The class combines ThingAccessClient and the thing that connects
 * to Link IoT Edge.
 */
class Connector {
  constructor(config, light) {
    this.config = config;
    this.light = light;
    this._client = new ThingAccessClient(config, {
      setProperties: this._setProperties.bind(this),
      getProperties: this._getProperties.bind(this),
      callService: this._callService.bind(this),
    });
  }

  /**
   * Connects to Link IoT Edge and publishes properties to it.
   */
  connect() {
    registerAndOnlineWithBackOffRetry(this._client, 1)
      .then(() => {
        return new Promise(() => {
          // Publish properties to Link IoT Edge platform.
          const properties = { 'LightSwitch': this.light.isOn ? 1 : 0 };
          this._client.reportProperties(properties);
        });
      })
      .catch(err => {
        console.log(err);
        return this._client.cleanup();
      })
      .catch(err => {
        console.log(err);
      });
  }

  /**
   * Disconnects from Link IoT Edge and stops publishing properties to it.
   */
  disconnect() {
    this._client.cleanup()
      .catch(err => {
        console.log(err);
      });
  }

  _setProperties(properties) {
    console.log('Set properties %s to thing %s-%s', JSON.stringify(properties),
      this.config.productKey, this.config.deviceName);
    if ('LightSwitch' in properties) {
      var value = properties['LightSwitch'];
      var isOn = value === 1;
      if (this.light.isOn !== isOn) {
        // Report new property to Link IoT Edge if it changed.
        this.light.isOn = isOn;
        if (this._client) {
          properties = {'LightSwitch': value};
          console.log(`Report properties: ${JSON.stringify(properties)}`);
          this._client.reportProperties(properties);
        }
      }
      return {
        code: RESULT_SUCCESS,
        message: 'success',
      };
    }
    return {
      code: RESULT_FAILURE,
      message: 'The requested properties does not exist.',
    };
  }

  _getProperties(keys) {
    console.log('Get properties %s from thing %s-%s', JSON.stringify(keys),
      this.config.productKey, this.config.deviceName);
    if (keys.includes('LightSwitch')) {
      return {
        code: RESULT_SUCCESS,
        message: 'success',
        params: {
          'LightSwitch': this.light.isOn ? 1 : 0,
        }
      };
    }
    return {
      code: RESULT_FAILURE,
      message: 'The requested properties does not exist.',
    }
  }

  _callService(name, args) {
    console.log('Call service %s with %s on thing %s-%s', JSON.stringify(name),
      JSON.stringify(args), this.config.productKey, this.config.deviceName);
    return {
      code: RESULT_FAILURE,
      message: 'The requested service does not exist.',
    };
  }
}

获取配置信息，并初始化Connector架构组件。

调用getConfig获取驱动配置。
调用getThingInfos获取设备信息及配置。
初始化Connector组件。
调用connect连接Link IoT Edge。

示例代码如下：

// Get the config which is auto-generated when devices are bound to this driver.
getConfig()
  .then((config) => {
    // Get the device information from config, which contains product key, device
    // name, etc. of the device.
    const thingInfos = config.getThingInfos();
    thingInfos.forEach((thingInfo) => {
      const light = new Light();
      // The ThingInfo format is just right for connector config, pass it directly.
      const connector = new Connector(thingInfo, light);
      connector.connect();
    });
  });

LightSensor

本示例演示一个模拟光照度传感器的驱动程序设计。

抽象模拟光照度传感器类。此处模拟光照度传感器有外部监听时会自动运行，在重置外部监听后会停止运行。

示例代码如下：

/**
 * A virtual light sensor which starts to publish illuminance between 100
 * and 600 with 100 delta changes once someone listen to it.
 */
class LightSensor {
  constructor() {
    this._illuminance = 200;
    this._delta = 100;
  }

  get illuminance() {
    return this._illuminance;
  }

  // Start to work.
  start() {
    if (this._clearInterval) {
      this._clearInterval();
    }
    console.log('Starting light sensor...');
    const timeout = setInterval(() => {
      // Update illuminance and delta.
      let delta = this._delta;
      let illuminance = this._illuminance;
      if (illuminance >= 600 || illuminance <= 100) {
        delta = -delta;
      }
      illuminance += delta;
      this._delta = delta;
      this._illuminance = illuminance;

      if (this._listener) {
        this._listener({
          properties: {
            illuminance,
          }
        });
      }
    }, 2000);
    this._clearInterval = () => {
      clearInterval(timeout);
      this._clearInterval = undefined;
    };
    return this._clearInterval;
  }

  stop() {
    console.log('Stopping light sensor ...');
    if (this._clearInterval) {
      this._clearInterval();
    }
  }

  listen(callback) {
    if (callback) {
      this._listener = callback;
      // Start to work when some one listen to this.
      this.start();
    } else {
      this._listener = undefined;
      this.stop();
    }
  }
}

实现Connector。

构造函数接收设备的配置参数和设备抽象对象，内部构造ThingAccessClient以便与Link IoT Edge交互。
实现ThingAccessClientCallbacks的3个回调方法，并在回调方法中调用设备对象接口与设备交互。
提供connect方法和disconnect方法。其中在connect方法里连接Link IoT Edge，在disconnect方法里断开设备与Link IoT Edge的连接。

示例代码如下：

/**
 * The class combines ThingAccessClient and the thing that connects to Link IoT Edge.
 */
class Connector {
  constructor(config, lightSensor) {
    this.config = config;
    this.lightSensor = lightSensor;
    this._client = new ThingAccessClient(config, {
      setProperties: this._setProperties.bind(this),
      getProperties: this._getProperties.bind(this),
      callService: this._callService.bind(this),
    });
  }

  /**
   * Connects to Link IoT Edge and publishes properties to it.
   */
  connect() {
    registerAndOnlineWithBackOffRetry(this._client, 1)
      .then(() => {
        return new Promise(() => {
          // Running..., listen to sensor, and report to Link IoT Edge.
          this.lightSensor.listen((data) => {
            const properties = {'MeasuredIlluminance': data.properties.illuminance};
            console.log(`Report properties: ${JSON.stringify(properties)}`);
            this._client.reportProperties(properties);
          });
        });
      })
      .catch(err => {
        console.log(err);
        return this._client.cleanup();
      })
      .catch(err => {
        console.log(err);
      });
  }

  /**
   * Disconnects from Link IoT Edge.
   */
  disconnect() {
    // Clean the listener.
    this.lightSensor.listen(undefined);
    this._client.cleanup()
      .catch(err => {
        console.log(err);
      });
  }

  _setProperties(properties) {
    console.log('Set properties %s to thing %s-%s', JSON.stringify(properties),
      this.config.productKey, this.config.deviceName);
    return {
      code: RESULT_FAILURE,
      message: 'The property is read-only.',
    };
  }

  _getProperties(keys) {
    console.log('Get properties %s from thing %s-%s', JSON.stringify(keys),
      this.config.productKey, this.config.deviceName);
    if (keys.includes('MeasuredIlluminance')) {
      return {
        code: RESULT_SUCCESS,
        message: 'success',
        params: {
          'MeasuredIlluminance': this.lightSensor.illuminance,
        }
      };
    }
    return {
      code: RESULT_FAILURE,
      message: 'The requested properties does not exist.',
    }
  }

  _callService(name, args) {
    console.log('Call service %s with %s on thing %s-%s', JSON.stringify(name),
      JSON.stringify(args), this.config.productKey, this.config.deviceName);
    return {
      code: RESULT_FAILURE,
      message: 'The requested service does not exist.',
    };
  }
}

获取配置信息，并初始化Connector架构组件。

调用getConfig获取驱动配置。
调用getThingInfos获取设备信息及配置。
初始化Connector组件。
调用connect连接Link IoT Edge。

示例代码如下：

// Get the config which is auto-generated when devices are bound to this driver.
getConfig()
  .then((config) => {
    // Get the device information from config, which contains product key, device
    // name, etc. of the device.
    const thingInfos = config.getThingInfos();
    thingInfos.forEach((thingInfo) => {
      const lightSensor = new LightSensor();
      // The ThingInfo format is just right for connector config, pass it directly.
      const connector = new Connector(thingInfo, lightSensor);
      connector.connect();
    });
  });