Java SPI Examples, ServiceLoader Example

Author: Pankaj Kumar

CoreJavaProjects/ServiceLoader-Example/pom.xml

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+<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<groupId>com.journaldev.java</groupId>
+	<artifactId>ServiceLoader-Example</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<configuration>
+					<source>11</source>
+					<target>11</target>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

CoreJavaProjects/ServiceLoader-Example/src/main/java/com/journaldev/serviceproviders/EmailServiceProvider.java

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+package com.journaldev.serviceproviders;
+
+public class EmailServiceProvider implements MessageServiceProvider {
+
+	public void sendMessage(String message) {
+		System.out.println("Sending Email with Message = "+message);
+	}
+
+}

CoreJavaProjects/ServiceLoader-Example/src/main/java/com/journaldev/serviceproviders/MessageServiceProvider.java

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+package com.journaldev.serviceproviders;
+
+public interface MessageServiceProvider {
+
+	void sendMessage(String message);
+}

CoreJavaProjects/ServiceLoader-Example/src/main/java/com/journaldev/serviceproviders/PushNotificationServiceProvider.java

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+package com.journaldev.serviceproviders;
+
+public class PushNotificationServiceProvider implements MessageServiceProvider {
+
+	public void sendMessage(String message) {
+		System.out.println("Sending Push Notification with Message = "+message);
+	}
+
+}

CoreJavaProjects/ServiceLoader-Example/src/main/java/com/journaldev/test/ServiceLoaderTest.java

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+package com.journaldev.test;
+
+import java.util.Optional;
+import java.util.ServiceLoader;
+
+import com.journaldev.serviceproviders.MessageServiceProvider;
+
+public class ServiceLoaderTest {
+
+	public static void main(String[] args) {
+		ServiceLoader<MessageServiceProvider> serviceLoader = ServiceLoader.load(MessageServiceProvider.class);
+
+		for (MessageServiceProvider service : serviceLoader) {
+			service.sendMessage("Hello");
+		}
+
+		// using Java 8 Optional to get the first service
+		Optional<MessageServiceProvider> firstService = serviceLoader.findFirst();
+		if (firstService.isPresent()) {
+			firstService.get().sendMessage("Hello Friend");
+		}
+
+		// using Java 8 forEach() method
+		serviceLoader.forEach((service) -> service.sendMessage("Have a Nice Day!"));
+
+		// Total Number of Loaded Services
+		System.out.println(serviceLoader.stream().count());
+		
+		
+
+	}
+
+}

CoreJavaProjects/ServiceLoader-Example/src/main/resources/META-INF/services/com.journaldev.serviceproviders.MessageServiceProvider

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+com.journaldev.serviceproviders.EmailServiceProvider
+com.journaldev.serviceproviders.PushNotificationServiceProvider