Feature/java http pubsub quickstarts (#534)

* code changes for pubsub using http request

Signed-off-by: Pravin Pushkar <ppushkar@microsoft.com>

* Removing .mvn files and fixing other review comments.

Signed-off-by: Pravin Pushkar <ppushkar@microsoft.com>

* Incorporating review comments

Signed-off-by: Pravin Pushkar <ppushkar@microsoft.com>

* Fixing README.md as suggested

Signed-off-by: Pravin Pushkar <ppushkar@microsoft.com>

pub_sub/java/.gitignore

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+## Maven
+target/
+release.properties
+.mvn
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+# IDE generated files and directories
+*.iml
+.idea/
+*.ipr
+*.iws
+.vs/
+.vscode/
+.code-workspace
+.settings/
+.metadata
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# macOS
+.DS_Store

pub_sub/java/http/README.md

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+# Dapr pub/sub
+
+In this quickstart, there is a publisher microservice `checkout` and a subscriber microservice `order-processor` to demonstrate how Dapr enables a publish-subscribe pattern. `checkout` generates messages and publishes to a specific orders topic, and `order-processor` subscribers listen for messages of topic orders.
+
+Visit [this](https://docs.dapr.io/developing-applications/building-blocks/pubsub/) link for more information about Dapr and Pub-Sub.
+
+> **Note:** This example leverages HTTPClient only.  If you are looking for the example using the Dapr Client SDK (recommended) [click here](../sdk).
+
+This quickstart includes one publisher:
+
+- Java client message generator `checkout`
+
+And one subscriber:
+
+- Java subscriber `order-processor`
+
+## Pre-requisites
+
+* [Dapr and Dapr Cli](https://docs.dapr.io/getting-started/install-dapr/).
+* Java JDK 11 (or greater): [Oracle JDK](https://www.oracle.com/technetwork/java/javase/downloads/index.html#JDK11) or [OpenJDK](https://jdk.java.net/11/).
+* [Apache Maven](https://maven.apache.org/install.html) version 3.x.
+
+### Run Java message publisher app with Dapr
+
+1. Open a new terminal window and navigate to `checkout` directory:
+
+```bash
+cd checkout
+```
+
+2. Install dependencies:
+
+```bash
+mvn clean install
+```
+
+3. Run the Java publisher app with Dapr:
+
+```bash
+ dapr run --app-id checkout --components-path ../../../components -- java -jar target/CheckoutService-0.0.1-SNAPSHOT.jar
+```
+
+### Run Java message subscriber app with Dapr
+
+1. Open a new terminal window and navigate to `order-processor` directory:
+
+```bash
+cd order-processor
+```
+
+2. Install dependencies:
+
+```bash
+mvn clean install
+```
+
+3. Run the Java subscriber app with Dapr:
+
+```bash
+ dapr run --app-port 8080 --app-id order-processor --components-path ../../../components -- java -jar target/OrderProcessingService-0.0.1-SNAPSHOT.jar
+```

pub_sub/java/http/checkout/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<groupId>com.service</groupId>
+	<artifactId>CheckoutService</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<description>Demo for Dapr pubsub component</description>
+	<properties>
+		<maven.compiler.source>11</maven.compiler.source>
+		<maven.compiler.target>11</maven.compiler.target>
+		<slf4jVersion>1.6.1</slf4jVersion>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>org.json</groupId>
+			<artifactId>json</artifactId>
+			<version>20211205</version>
+		</dependency>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-api</artifactId>
+			<version>${slf4jVersion}</version>
+		</dependency>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-simple</artifactId>
+			<version>${slf4jVersion}</version>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+				<executions>
+					<execution>
+						<goals>
+							<goal>repackage</goal>
+						</goals>
+						<configuration>
+							<mainClass>
+								com.service.CheckoutServiceApplication
+							</mainClass>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

pub_sub/java/http/checkout/src/main/java/com/service/CheckoutServiceApplication.java

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+package com.service;
+
+import org.json.JSONObject;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+
+public class CheckoutServiceApplication {
+	private static final Logger logger = LoggerFactory.getLogger(CheckoutServiceApplication.class);
+	private static final HttpClient httpClient = HttpClient.newBuilder()
+			.version(HttpClient.Version.HTTP_2)
+			.connectTimeout(Duration.ofSeconds(10))
+			.build();
+
+	private static final String PUBSUB_NAME = "order_pub_sub";
+	private static final String TOPIC = "orders";
+	private static String DAPR_HOST = System.getenv().getOrDefault("DAPR_HOST", "http://localhost");
+	private static String DAPR_HTTP_PORT = System.getenv().getOrDefault("DAPR_HTTP_PORT", "3500");
+
+	public static void main(String[] args) throws InterruptedException, IOException {
+		String uri = DAPR_HOST +":"+ DAPR_HTTP_PORT + "/v1.0/publish/"+PUBSUB_NAME+"/"+TOPIC;
+		while (true) {
+			Random random = new Random();
+			int orderId = random.nextInt(1000 - 1) + 1;
+			JSONObject obj = new JSONObject();
+			obj.put("orderId", orderId);
+
+			// Publish an event/message using Dapr PubSub via HTTP Post
+			HttpRequest request = HttpRequest.newBuilder()
+					.POST(HttpRequest.BodyPublishers.ofString(obj.toString()))
+					.uri(URI.create(uri))
+					.header("Content-Type", "application/json")
+					.build();
+
+			HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
+			logger.info("Published data: {}", orderId);
+			TimeUnit.MILLISECONDS.sleep(3000);
+		}
+	}
+}

pub_sub/java/http/order-processor/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.6.3</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>com.service</groupId>
+	<artifactId>OrderProcessingService</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>OrderProcessingService</name>
+	<description>Demo for Dapr pubsub component</description>
+	<properties>
+		<java.version>11</java.version>
+	</properties>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.projectlombok</groupId>
+			<artifactId>lombok</artifactId>
+			<optional>true</optional>
+		</dependency>
+	</dependencies>
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

pub_sub/java/http/order-processor/src/main/java/com/service/OrderProcessingServiceApplication.java

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+package com.service;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class OrderProcessingServiceApplication {
+	public static void main(String[] args) {
+		SpringApplication.run(OrderProcessingServiceApplication.class, args);
+	}
+}

pub_sub/java/http/order-processor/src/main/java/com/service/controller/OrderProcessingServiceController.java

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+package com.service.controller;
+
+import com.service.model.DaprSubscription;
+import com.service.model.Order;
+import com.service.model.SubscriptionData;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class OrderProcessingServiceController {
+    private static final Logger logger = LoggerFactory.getLogger(OrderProcessingServiceController.class);
+
+    /**
+     * Register Dapr pub/sub subscriptions.
+     *
+     * @return DaprSubscription Object containing pubsub name, topic and route for subscription.
+     */
+    @GetMapping(path = "/dapr/subscribe", produces = MediaType.APPLICATION_JSON_VALUE)
+    public DaprSubscription[] getSubscription() {
+        DaprSubscription daprSubscription = DaprSubscription.builder()
+                .pubSubName("order_pub_sub")
+                .topic("orders")
+                .route("orders")
+                .build();
+        logger.info("Subscribed to Pubsubname {} and topic {}", "order_pub_sub", "orders");
+        DaprSubscription[] arr = new DaprSubscription[]{daprSubscription};
+        return arr;
+    }
+
+    /**
+     * Dapr subscription in /dapr/subscribe sets up this route.
+     *
+     * @param body Request body
+     * @return ResponseEntity Returns ResponseEntity.ok()
+     */
+    @PostMapping(path = "/orders", consumes = MediaType.ALL_VALUE)
+    public ResponseEntity<?> processOrders(@RequestBody SubscriptionData<Order> body) {
+        logger.info("Subscriber received: "+ body.getData().getOrderId());
+        return ResponseEntity.ok().build();
+    }
+}

pub_sub/java/http/order-processor/src/main/java/com/service/model/DaprSubscription.java

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+package com.service.model;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Builder
+@Getter
+public class DaprSubscription {
+    private String pubSubName;
+    private String topic;
+    private String route;
+}

pub_sub/java/http/order-processor/src/main/java/com/service/model/Order.java

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+package com.service.model;
+
+import lombok.Getter;
+import lombok.Setter;
+
+/**
+ * A class to represent the data object that is being passed to subscribe endpoint.
+ */
+@Getter
+@Setter
+public class Order {
+    private int orderId;
+}

pub_sub/java/http/order-processor/src/main/java/com/service/model/SubscriptionData.java

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+package com.service.model;
+
+import lombok.Getter;
+import lombok.Setter;
+
+/**
+ * Helps in unpacking a cloud event which Checkout application generates.
+ *
+ * @param <T> Type of data being passed to subscriber end point(orderProcessor app)
+ */
+@Getter
+@Setter
+public class SubscriptionData<T> {
+    private T data;
+}

pub_sub/java/http/order-processor/src/main/resources/application.properties

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+