Dapr Java HTTP call

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

Version introduction

  • Java edition :8
  • Dapr Java SKD edition :0.9.2

Dapr Java-SDK HTTP Call document There is a prerequisite , The contents are as follows :

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

We see Java JDK The minimum requirement for version is 11, But this article shows what you use JDK 8, What is the reason for that , Sure Reference resources Java-SDK Issues,Issues The answer is as follows :

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

It means they want to pass Java 11 Write application validation Java 8 Written SDK Whether it can be used normally . This article does not need to verify Java 11 Can you use Java-SDK , So this article will use Java 8 Building the application .

Engineering structure

3 Sub project , One client, Two service. Two new service The point is to show http Link call uses dapr How to achieve .3 All the projects are integrated Spring Boot.Spring Boot Automatically register after startup Controller、Config And so on. 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 Call as client java-service-b;
  2. java-service-b Receiving request , And call java-service-c;
  3. java-service-c Receiving request , And respond to ;
  4. java-service-b received java-service-c The reply , And respond to java-client-a request .


java-service-c As http Call the end of the link , Just listen http The request can be .

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); Integrate SpringBoot start-up .

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));

Start command :

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 You need to configure a DaprClient Bean, To use... When needed Http Injection of client places .

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();

Next, what you need to call Controller Add constructor injection to .

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

launch http request .

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

Start command :

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


about java-client-a Come on , Integrate Springboot Optional. , Here, construct a every 5 Second, the client that initiated a request .

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) {

Start command :

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


The starting sequence of each module shall be :

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

The reason why the order is limited here is , If you start first java-client-a ,java-client-a It will pass immediately dapr Start to initiate a request to java-service-b , And then java-service-b Didn't start . This will trigger dapr The retry mechanism of .


Service calls when event call fails and transient errors , The interval between the execution and the backoff time is (backoff time periods) Automatic retry of .
Error causing retry :

  • Network error , Including terminal unavailable and denial of connection .
  • Authentication error , Because on caller / Of the callee dapr The side car certificate update results in .

Every time you try again, you will 1 The time of seconds is interval , The maximum number of retries is 3 Time . And the destination side car passes through gRPC Establishing a connection 5 Second timeout .

java-client-a Print :

== 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 Print :

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

java-service-c Print :

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

Open a new command line window , Input dapr list

Start example

Source code address :https://github.com/ZhangX-Byte/dapr-java

Cloning of warehouse

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

structure dapr-java project

mvn install

Then each project is install It will start up normally .


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