操作方法：使用输出绑定连接外部资源

通过输出绑定调用外部系统

使用输出绑定，您可以调用外部资源。 调用请求可发送可选的有效载荷和元数据。

本指南以 Kafka 绑定为例。 您可以从绑定组件列表} 中找到自己喜欢的绑定规范。 在本指南中

1. 该示例调用了 /binding 端点，其中 checkout，即要调用的绑定名称。
2. 有效载荷位于必需的 data 字段中，并且可以是任何 JSON 可序列化的值。
3. operation字段告诉绑定需要采取什么操作。 例如，Kafka绑定支持create操作。
   • 您可以查看每个输出绑定支持的操作（针对每个组件）。

注意

如果你还没有，请尝试使用绑定快速入门快速了解如何使用绑定 API。

创建绑定

创建一个 binding.yaml 文件，并将其保存到应用程序目录中的 components 子文件夹中。

创建一个名称为 checkout 的新绑定组件。 在metadata部分，配置以下与Kafka相关的属性：

• 您要发布信息的主题
• Broker

在创建绑定组件时，请指定支持的绑定direction（方向）。

• Self-Hosted (CLI)
• Kubernetes

使用 --resources-path 标志与 dapr run 命令一起使用，指向您的自定义资源目录。

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: checkout
spec:
  type: bindings.kafka
  version: v1
  metadata:
  # Kafka broker connection setting
  - name: brokers
    value: localhost:9092
  # consumer configuration: topic and consumer group
  - name: topics
    value: sample
  - name: consumerGroup
    value: group1
  # publisher configuration: topic
  - name: publishTopic
    value: sample
  - name: authRequired
    value: false
  - name: direction
    value: output

要将以下 binding.yaml 文件部署到 Kubernetes 集群中，请运行 kubectl apply -f binding.yaml。

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: checkout
spec:
  type: bindings.kafka
  version: v1
  metadata:
  # Kafka broker connection setting
  - name: brokers
    value: localhost:9092
  # consumer configuration: topic and consumer group
  - name: topics
    value: sample
  - name: consumerGroup
    value: group1
  # publisher configuration: topic
  - name: publishTopic
    value: sample
  - name: authRequired
    value: false
  - name: direction
    value: output

发送事件（输出绑定）

下面的代码示例利用 Dapr SDK 在运行中的 Dapr 实例上调用输出绑定端点。

• Dotnet
• Java
• Python
• Go
• JavaScript

//dependencies
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;
using Dapr.Client;
using Microsoft.AspNetCore.Mvc;
using System.Threading;
//code
namespace EventService
{
    class Program
    {
        static async Task Main(string[] args)
        {
            string BINDING_NAME = "checkout";
            string BINDING_OPERATION = "create";
            while(true)
            {
                System.Threading.Thread.Sleep(5000);
                Random random = new Random();
                int orderId = random.Next(1,1000);
                using var client = new DaprClientBuilder().Build();
                //Using Dapr SDK to invoke output binding
                await client.InvokeBindingAsync(BINDING_NAME, BINDING_OPERATION, orderId);
                Console.WriteLine("Sending message: " + orderId);
            }
        }
    }
}

//dependencies
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.domain.HttpExtension;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Random;
import java.util.concurrent.TimeUnit;
//code
@SpringBootApplication
public class OrderProcessingServiceApplication {
    private static final Logger log = LoggerFactory.getLogger(OrderProcessingServiceApplication.class);
    public static void main(String[] args) throws InterruptedException{
        String BINDING_NAME = "checkout";
        String BINDING_OPERATION = "create";
        while(true) {
            TimeUnit.MILLISECONDS.sleep(5000);
            Random random = new Random();
            int orderId = random.nextInt(1000-1) + 1;
            DaprClient client = new DaprClientBuilder().build();
          //Using Dapr SDK to invoke output binding
            client.invokeBinding(BINDING_NAME, BINDING_OPERATION, orderId).block();
            log.info("Sending message: " + orderId);
        }
    }
}

#dependencies
import random
from time import sleep    
import requests
import logging
import json
from dapr.clients import DaprClient
#code
logging.basicConfig(level = logging.INFO)
BINDING_NAME = 'checkout'
BINDING_OPERATION = 'create' 
while True:
    sleep(random.randrange(50, 5000) / 1000)
    orderId = random.randint(1, 1000)
    with DaprClient() as client:
        #Using Dapr SDK to invoke output binding
        resp = client.invoke_binding(BINDING_NAME, BINDING_OPERATION, json.dumps(orderId))
    logging.basicConfig(level = logging.INFO)
    logging.info('Sending message: ' + str(orderId))

//dependencies
import (
    "context"
    "log"
    "math/rand"
    "time"
    "strconv"
    dapr "github.com/dapr/go-sdk/client"
)
//code
func main() {
    BINDING_NAME := "checkout";
    BINDING_OPERATION := "create";
    for i := 0; i < 10; i++ {
        time.Sleep(5000)
        orderId := rand.Intn(1000-1) + 1
        client, err := dapr.NewClient()
        if err != nil {
            panic(err)
        }
        defer client.Close()
        ctx := context.Background()
        //Using Dapr SDK to invoke output binding
        in := &dapr.InvokeBindingRequest{ Name: BINDING_NAME, Operation: BINDING_OPERATION , Data: []byte(strconv.Itoa(orderId))}
        err = client.InvokeOutputBinding(ctx, in)
        log.Println("Sending message: " + strconv.Itoa(orderId))
    }
}

//dependencies
import { DaprClient, CommunicationProtocolEnum } from "@dapr/dapr";
//code
const daprHost = "127.0.0.1";
(async function () {
    for (var i = 0; i < 10; i++) {
        await sleep(2000);
        const orderId = Math.floor(Math.random() * (1000 - 1) + 1);
        try {
            await sendOrder(orderId)
        } catch (err) {
            console.error(e);
            process.exit(1);
        }
    }
})();
async function sendOrder(orderId) {
    const BINDING_NAME = "checkout";
    const BINDING_OPERATION = "create";
    const client = new DaprClient({
        daprHost,
        daprPort: process.env.DAPR_HTTP_PORT,
        communicationProtocol: CommunicationProtocolEnum.HTTP,
    });
    //Using Dapr SDK to invoke output binding
    const result = await client.binding.send(BINDING_NAME, BINDING_OPERATION, orderId);
    console.log("Sending message: " + orderId);
}
function sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
}

还可以使用 HTTP 调用输出绑定端点：

curl -X POST -H 'Content-Type: application/json' http://localhost:3601/v1.0/bindings/checkout -d '{ "data": 100, "operation": "create" }'

观看这个视频，了解如何使用双向输出绑定。

参考资料

• 绑定API
• 绑定组件
• 支持的绑定列表