Bael 4700 (#10231)

* Added code examples from the article.

* Hide the revoked token

* Reduce long line break indentation to 2 spaces, change "your" to "our," and use the -LiveTest convention for the test class.

* Reduce Java version from 11 to 1.8 and add the new discord4j module to the root pom.

* Remove test due to context failing to start up without a valid bot token.

* Replace test class and add error handling for invalid tokens.

discord4j/.gitignore

@@ -0,0 +1,33 @@
+README.md
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/

discord4j/pom.xml

@@ -0,0 +1,63 @@
+<?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>2.3.5.RELEASE</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>com.baeldung</groupId>
+	<artifactId>discord4j-bot</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>discord4j-bot</name>
+	<description>Demo Discord bot using Discord4J + Spring Boot</description>
+
+	<properties>
+		<java.version>1.8</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+			<exclusions>
+				<exclusion>
+					<groupId>org.junit.vintage</groupId>
+					<artifactId>junit-vintage-engine</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+
+		<dependency>
+			<groupId>com.discord4j</groupId>
+			<artifactId>discord4j-core</artifactId>
+			<version>3.1.1</version>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<configuration>
+					<source>1.8</source>
+					<target>1.8</target>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

discord4j/src/main/java/com/baeldung/discordbot/BotConfiguration.java

@@ -0,0 +1,48 @@
+package com.baeldung.discordbot;
+
+import com.baeldung.discordbot.events.EventListener;
+import discord4j.core.DiscordClientBuilder;
+import discord4j.core.GatewayDiscordClient;
+import discord4j.core.event.domain.Event;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import java.util.List;
+
+@Configuration
+public class BotConfiguration {
+
+    private static final Logger log = LoggerFactory.getLogger( BotConfiguration.class );
+
+    @Value("${token}")
+    private String token;
+
+    @Bean
+    public <T extends Event> GatewayDiscordClient gatewayDiscordClient(List<EventListener<T>> eventListeners) {
+        GatewayDiscordClient client = null;
+
+        try {
+            client = DiscordClientBuilder.create(token)
+              .build()
+              .login()
+              .block();
+
+            for(EventListener<T> listener : eventListeners) {
+                client.on(listener.getEventType())
+                  .flatMap(listener::execute)
+                  .onErrorResume(listener::handleError)
+                  .subscribe();
+            }
+
+            client.onDisconnect().block();
+        }
+        catch ( Exception exception ) {
+            log.error( "Be sure to use a valid bot token!", exception );
+        }
+
+        return client;
+    }
+}

discord4j/src/main/java/com/baeldung/discordbot/DiscordBotApplication.java

@@ -0,0 +1,12 @@
+package com.baeldung.discordbot;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class DiscordBotApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(DiscordBotApplication.class, args);
+	}
+}

discord4j/src/main/java/com/baeldung/discordbot/events/EventListener.java

@@ -0,0 +1,19 @@
+package com.baeldung.discordbot.events;
+
+import discord4j.core.event.domain.Event;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import reactor.core.publisher.Mono;
+
+public interface EventListener<T extends Event> {
+
+    Logger LOG = LoggerFactory.getLogger(EventListener.class);
+
+    Class<T> getEventType();
+    Mono<Void> execute(T event);
+
+    default Mono<Void> handleError(Throwable error) {
+        LOG.error("Unable to process " + getEventType().getSimpleName(), error);
+        return Mono.empty();
+    }
+}

discord4j/src/main/java/com/baeldung/discordbot/events/MessageCreateListener.java

@@ -0,0 +1,19 @@
+package com.baeldung.discordbot.events;
+
+import discord4j.core.event.domain.message.MessageCreateEvent;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Mono;
+
+@Service
+public class MessageCreateListener extends MessageListener implements EventListener<MessageCreateEvent> {
+
+    @Override
+    public Class<MessageCreateEvent> getEventType() {
+        return MessageCreateEvent.class;
+    }
+
+    @Override
+    public Mono<Void> execute(MessageCreateEvent event) {
+        return processCommand(event.getMessage());
+    }
+}

discord4j/src/main/java/com/baeldung/discordbot/events/MessageListener.java

@@ -0,0 +1,19 @@
+package com.baeldung.discordbot.events;
+
+import discord4j.core.object.entity.Message;
+import reactor.core.publisher.Mono;
+
+public abstract class MessageListener {
+
+    public Mono<Void> processCommand(Message eventMessage) {
+        return Mono.just(eventMessage)
+           .filter(message -> message.getAuthor().map(user -> !user.isBot()).orElse(false))
+           .filter(message -> message.getContent().equalsIgnoreCase("!todo"))
+           .flatMap(Message::getChannel)
+           .flatMap(channel -> channel.createMessage("Things to do today:\n" +
+                                                     " - write a bot\n" +
+                                                     " - eat lunch\n" +
+                                                     " - play a game"))
+           .then();
+    }
+}

discord4j/src/main/java/com/baeldung/discordbot/events/MessageUpdateListener.java

@@ -0,0 +1,22 @@
+package com.baeldung.discordbot.events;
+
+import discord4j.core.event.domain.message.MessageUpdateEvent;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Mono;
+
+@Service
+public class MessageUpdateListener extends MessageListener implements EventListener<MessageUpdateEvent> {
+
+    @Override
+    public Class<MessageUpdateEvent> getEventType() {
+        return MessageUpdateEvent.class;
+    }
+
+    @Override
+    public Mono<Void> execute(MessageUpdateEvent event) {
+        return Mono.just(event)
+           .filter(MessageUpdateEvent::isContentChanged)
+           .flatMap(MessageUpdateEvent::getMessage)
+           .flatMap(super::processCommand);
+    }
+}

discord4j/src/main/resources/application.yml

@@ -0,0 +1 @@
+token: 'our-token-here'

discord4j/src/test/java/com/baeldung/discordbot/DiscordBotLiveTest.java

@@ -0,0 +1,12 @@
+package com.baeldung.discordbot;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+public class DiscordBotLiveTest {
+
+    @Test
+    public void contextTest() {
+    }
+}

pom.xml

@@ -397,6 +397,7 @@
                 <module>ddd</module>
                 <!-- <module>ddd-modules</module>--> <!-- we haven't upgraded to Java 9 -->
                 <module>deeplearning4j</module>
+                <module>discord4j</module>
                 <module>disruptor</module>
                 <module>dozer</module>
                 <module>drools</module>
@@ -909,6 +910,7 @@
                 <module>ddd</module>
                 <!-- <module>ddd-modules</module>--> <!-- we haven't upgraded to Java 9 -->
                 <module>deeplearning4j</module>
+                <module>discord4j</module>
                 <module>disruptor</module>
                 <module>dozer</module>
                 <module>drools</module>