Dapr Java Http 调用

Zhang_Xiang 2020-11-08 16:37:45
java http dapr 调用


  • Java 版本:8
  • Dapr Java SKD 版本:0.9.2

Dapr Java-SDK HTTP 调用文档 有个先决条件,内容如下:

  • Dapr and Dapr CLI.
  • Java JDK 11 (or greater): Oracle JDK or OpenJDK.
  • Apache Maven version 3.x.

大家看到 Java JDK 版本最低要求是 11,但是本文显示使用的 JDK 8,这么做的原因是什么呢,可以参考 Java-SDK Issues,Issues 中回答如下:

We want to validate that the SDK is built with Java 8 and apps can use it with Java 11.

意思是他们想通过 Java 11 写的应用程序验证 Java 8 写的 SDK 是否能正常使用。本文不需要验证 Java 11 能否使用 Java-SDK ,因此本文将使用 Java 8 构建应用程序。


3 个子工程,一个 client,两个 service。新建两个 service 的意义在于展示 http 链路调用使用 dapr 如何实现。3 个工程项目都集成了 Spring Boot。Spring Boot 启动后会自动注册 Controller、Config 之类的 bean。

graph LR; java-client-a--1-->java-service-b; java-service-b--2-->java-service-c; java-service-c--3-->java-service-b; java-service-b--4-->java-client-a;
  1. java-client-a 做为客户端调用 java-service-b;
  2. java-service-b 接收请求,并调用 java-service-c;
  3. java-service-c 接收请求,并响应;
  4. java-service-b 收到 java-service-c 应答,并响应 java-client-a 请求。


java-service-c 做为 http 调用链路末端,只需监听 http 请求即可。

package com.dapr.service;
import org.apache.commons.cli.CommandLine;
import org.apache.commons.cli.CommandLineParser;
import org.apache.commons.cli.DefaultParser;
import org.apache.commons.cli.Options;
* @author Zhang_Xiang
* @since 2020/11/7 10:51:22
public class ServiceC {
* Starts the service.
* @param args Expects the port: -p PORT
* @throws Exception If cannot start service.
public static void main(String[] args) throws Exception {
Options options = new Options();
options.addRequiredOption("p", "port", true, "Port to listen to.");
CommandLineParser parser = new DefaultParser();
CommandLine cmd = parser.parse(options, args);
// If port string is not valid, it will throw an exception.
int port = Integer.parseInt(cmd.getOptionValue("port"));

DaprApplication.start(port); 集成 SpringBoot 启动。

package com.dapr.service;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
* Dapr's HTTP callback implementation via SpringBoot.
* Scanning package io.dapr.springboot is required.
* @author zhangxiang
@SpringBootApplication(scanBasePackages = {"com.dapr.service"})
public class DaprApplication {
* Starts Dapr's callback in a given port.
* @param port Port to listen to.
public static void start(int port) {
SpringApplication app = new SpringApplication(DaprApplication.class);
app.run(String.format("--server.port=%d", port));


dapr run --app-id java-service-c --app-port 9100 --dapr-http-port 3510 -- java -jar target/dapr-java-service-exec.jar com.dapr.service.ServiceC -p 9100


java-service-b 需要配置一个 DaprClient Bean,以在需要使用 Http 客户端的地方注入。

package com.dapr.service.config;
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
* @author Zhang_Xiang
* @since 2020/11/8 08:46:49
public class Client {
public DaprClient getClient(){
return (new DaprClientBuilder()).build();

接下来在需要调用的 Controller 中添加构造器注入。

* SpringBoot Controller to handle input binding.
* @author zhangxiang
public class HelloController {
private final DaprClient client;
public HelloController(DaprClient client) {
this.client = client;

发起 http 请求。

byte[] response = client.invokeService(SERVICE_APP_ID, "say", message, HttpExtension.POST, null,
if (response != null) {


dapr run --app-id java-service-b --app-port 9101 --dapr-http-port 3511 -- java -jar target/dapr-java-service-exec.jar com.dapr.service.ServiceB -p 9101


对于 java-client-a 来说,集成 Springboot 是可选项,此处构造一个每隔 5 秒发起一次请求的客户端。

package com.dapr.client;
import com.alibaba.fastjson.JSON;
import com.common.ResponseResult;
import io.dapr.client.DaprClient;
import io.dapr.client.DaprClientBuilder;
import io.dapr.client.domain.HttpExtension;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.TimeZone;
* @author Zhang_Xiang
* @since 2020/11/7 17:30:26
public class ClientA {
* Identifier in Dapr for the service this client will invoke.
private static final String SERVICE_APP_ID = "java-service-b";
* Format to output date and time.
private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
* Starts the invoke client.
* @param args Messages to be sent as request for the invoke API.
public static void main(String[] args) throws IOException {
try (DaprClient client = (new DaprClientBuilder()).build()) {
while (true) {
Calendar utcNow = Calendar.getInstance(TimeZone.getTimeZone("GMT"));
String utcNowAsString = DATE_FORMAT.format(utcNow.getTime());
String msg = String.format("%s:this this java client A", utcNowAsString);
byte[] response = client.invokeService(SERVICE_APP_ID, "say", msg.getBytes(), HttpExtension.POST, null,
if (response != null) {
String responseResultStr = new String(response);
ResponseResult responseResult = JSON.parseObject(responseResultStr, ResponseResult.class);
try {
} catch (InterruptedException e) {


dapr run --app-id java-client-a --dapr-http-port 3006 -- java -jar target/dapr-java-client-exec.jar com.dapr.client.ClientA



graph LR; java-service-c-->java-service-b; java-service-b-->java-client-a;

这里限定顺序的原因是,如果先启动 java-client-a ,java-client-a 会立刻通过 dapr 开始发起请求到 java-service-b ,而这时 java-service-b 并未启动。这将触发 dapr 的重试机制。


服务调用在事件调用失败和瞬态错误时,将执行带避退时间间隔(backoff time periods)的自动重试。

  • 网络错误,包括终端不可用和拒绝连接。
  • 身份认证错误,由于在调用方/被调用方的 dapr 边车证书更新导致。

每次重试都以 1 秒的时间避退时间为间隔,最大重试次数为 3 次。和目的地边车通过 gRPC 建立连接 5 秒超时。

java-client-a 打印:

== APP == This is java-service-b,receive the message:2020-11-08 14:21:14.336:this this java client A,and request java-service-c get the response:{"message":"This is java-service-c,receive the message:\"2020-11-08 14:21:14.336:this this java client A\""}

java-service-b 打印:

== APP == This is java-service-b,receive the message:2020-11-08 14:21:44.454:this this java client A

java-service-c 打印:

== APP == This is java-service-c,receive the message:"2020-11-08 14:22:19.571:this this java client A"

打开新的命令行窗口,输入 dapr list




git clone https://github.com/ZhangX-Byte/dapr-java.git
cd dapr-java

构建 dapr-java 项目

mvn install

然后各个项目各自 install 就能正常启动了。


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