Pull Guice usage example from repo: https://github.com/andrei-punko/java-interview-coding

Author: andrei-punko

common/pom.xml

@@ -26,6 +26,13 @@
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
         </dependency>
+
+        <!-- Guice -->
+        <dependency>
+            <groupId>com.google.inject</groupId>
+            <artifactId>guice</artifactId>
+            <version>5.1.0</version>
+        </dependency>
     </dependencies>
 
     <build>

common/src/main/java/by/andd3dfx/guice/Count.java

@@ -0,0 +1,12 @@
+package by.andd3dfx.guice;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import javax.inject.Qualifier;
+
+@Qualifier
+@Retention(RUNTIME)
+@interface Count {
+
+}

common/src/main/java/by/andd3dfx/guice/DemoModule.java

@@ -0,0 +1,32 @@
+package by.andd3dfx.guice;
+
+import by.andd3dfx.guice.util.Communicator;
+import by.andd3dfx.guice.util.DefaultCommunicatorImpl;
+import by.andd3dfx.guice.util.Spawner;
+import by.andd3dfx.guice.util.SpawnerImpl;
+import com.google.inject.AbstractModule;
+import com.google.inject.Provides;
+
+/**
+ * Guice module that provides bindings for message and count used in {@link Greeter}.
+ */
+public class DemoModule extends AbstractModule {
+
+    @Provides
+    @Count
+    static Integer provideCount() {
+        return 3;
+    }
+
+    @Provides
+    @Message
+    static String provideMessage() {
+        return "hello world";
+    }
+
+    @Override
+    protected void configure() {
+        bind(Communicator.class).to(DefaultCommunicatorImpl.class);
+        bind(Spawner.class).to(SpawnerImpl.class);
+    }
+}

common/src/main/java/by/andd3dfx/guice/Greeter.java

@@ -0,0 +1,45 @@
+package by.andd3dfx.guice;
+
+import by.andd3dfx.guice.util.Communicator;
+import by.andd3dfx.guice.util.Spawner;
+import javax.inject.Inject;
+
+public class Greeter {
+
+    private final String message;
+    private final int count;
+    private Communicator communicator;
+
+    // Field injection example
+    @Inject
+    private Spawner spawner;
+
+    // Constructor injection example
+    // Greeter declares that it needs a string message and an integer representing the number of time the message to be printed.
+    // The @Inject annotation marks this constructor as eligible to be used by Guice
+    @Inject
+    public Greeter(@Message String message, @Count int count) {
+        this.message = message;
+        this.count = count;
+    }
+
+    // Method injection example
+    @Inject
+    public void setCommunicator(Communicator communicator) {
+        this.communicator = communicator;
+    }
+
+    public void sayHello() {
+        for (int i = 0; i < count; i++) {
+            System.out.println(message);
+        }
+    }
+
+    public void communicate() {
+        communicator.communicate();
+    }
+
+    public void spawn() {
+        spawner.spawn();
+    }
+}

common/src/main/java/by/andd3dfx/guice/GuiceDemo.java

@@ -0,0 +1,41 @@
+package by.andd3dfx.guice;
+
+import by.andd3dfx.guice.util.Communicator;
+import by.andd3dfx.guice.util.Spawner;
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+
+/**
+ * According to Guice "Getting Started" page: https://github.com/google/guice/wiki/GettingStarted
+ * <p>
+ * and Baeldung Guice manual: https://www.baeldung.com/guice
+ */
+public class GuiceDemo {
+
+    public static void main(String[] args) {
+        /*
+         * Guice.createInjector() takes one or more modules, and returns a new Injector
+         * instance. Most applications will call this method exactly once, in their
+         * main() method.
+         */
+        Injector injector = Guice.createInjector(new DemoModule());
+
+        /*
+         * Now that we've got the injector, we can build objects.
+         */
+        Greeter greeter = injector.getInstance(Greeter.class);
+
+        // Prints "hello world" 3 times to the console.
+        greeter.sayHello();
+        greeter.communicate();
+        greeter.spawn();
+
+        // Make communication
+        Communicator communicator = injector.getInstance(Communicator.class);
+        communicator.communicate();
+
+        // Make some spawning
+        Spawner spawner = injector.getInstance(Spawner.class);
+        spawner.spawn();
+    }
+}

common/src/main/java/by/andd3dfx/guice/Message.java

@@ -0,0 +1,12 @@
+package by.andd3dfx.guice;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import javax.inject.Qualifier;
+
+@Qualifier
+@Retention(RUNTIME)
+@interface Message {
+
+}

common/src/main/java/by/andd3dfx/guice/util/Communicator.java

@@ -0,0 +1,6 @@
+package by.andd3dfx.guice.util;
+
+public interface Communicator {
+
+    void communicate();
+}

common/src/main/java/by/andd3dfx/guice/util/DefaultCommunicatorImpl.java

@@ -0,0 +1,9 @@
+package by.andd3dfx.guice.util;
+
+public class DefaultCommunicatorImpl implements Communicator {
+
+    @Override
+    public void communicate() {
+        System.out.println("Making friendly communication...");
+    }
+}

common/src/main/java/by/andd3dfx/guice/util/Spawner.java

@@ -0,0 +1,6 @@
+package by.andd3dfx.guice.util;
+
+public interface Spawner {
+
+    void spawn();
+}

common/src/main/java/by/andd3dfx/guice/util/SpawnerImpl.java

@@ -0,0 +1,9 @@
+package by.andd3dfx.guice.util;
+
+public class SpawnerImpl implements Spawner {
+
+    @Override
+    public void spawn() {
+        System.out.println("Spawn something useful...");
+    }
+}