Feat. Added simple dependency injector auxiliary class

Author: sleipnir

README.md

@@ -6,6 +6,7 @@ JVM User Language Support for [Spawn](https://github.com/eigr/spawn).
 1. [Overview](#overview)
 2. [Getting Started](#getting-started)
 3. [Advanced Use Cases](#advanced-use-cases)
+    - [Dependency Injection](#dependency-injection)
     - [Types of Actors](#types-of-actors)
     - [Stateless Actors](#stateless-actors)
     - [Considerations about Spawn actors](#considerations-about-spawn-actors)
@@ -14,16 +15,16 @@ JVM User Language Support for [Spawn](https://github.com/eigr/spawn).
     - [Forward](#forward)
     - [Pipe](#pipe)
     - [State Management](#state-management)
-4. [Using Actors](#using-actors)
+5. [Using Actors](#using-actors)
     - [Call Named Actors](#call-named-actors)
     - [Call Unnamed Actors](#call-unnamed-actors)
     - [Async](#async)
     - [Timeouts](#timeouts)
-5. [Deploy](#deploy)
+6. [Deploy](#deploy)
     - [Defining an ActorSystem](#defining-an-actorsystem)
     - [Defining an ActorHost](#defining-an-actorhost)
     - [Activators](#activators)
-6. [Actor Model](#actor-model)
+7. [Actor Model](#actor-model)
     - [Virtual Actors](#virtual-actors)
 
 
@@ -93,7 +94,7 @@ The second thing we have to do is add the spawn dependency to the project.
 <dependency>
    <groupId>com.github.eigr</groupId>
    <artifactId>spawn-java-std-sdk</artifactId>
-   <version>v0.9.1</version>
+   <version>v1.0.0</version>
 </dependency>
 ```
 We're also going to configure a few things for our application build to work, including compiling the protobuf files. 
@@ -127,7 +128,7 @@ See below a full example of the pom.xml file:
       <dependency>
          <groupId>com.github.eigr</groupId>
          <artifactId>spawn-java-std-sdk</artifactId>
-         <version>v0.9.1</version>
+         <version>v1.0.0</version>
       </dependency>
       <dependency>
          <groupId>ch.qos.logback</groupId>
@@ -518,6 +519,102 @@ Spawn Actors abstract a huge amount of developer infrastructure and can be used
 In the sections below we will demonstrate some features available in Spawn that contribute to the development of 
 complex applications in a simplified way.
 
+### Dependency Injection
+
+Sometimes we need to pass many arguments as dependencies to the Actor class.
+In this case, it is more convenient to use your own dependency injection mechanism.
+However, the Spawn SDK already comes with an auxiliary class to make this easier for the developer.
+Let's look at an example:
+
+1. First let's take a look at some example dependency classes:
+
+```java
+// We will have an interface that represents any type of service.
+public interface MessageService {
+   String getDefaultMessage();
+}
+
+// and concrete implementation here
+public class MessageServiceImpl implements MessageService {
+   @Override
+   public String getDefaultMessage() {
+      return "Hello Spawn in English";
+   }
+}
+```
+
+2. Second, let's define an actor so that it receives an instance of the DependencyInjector class through the class constructor:
+
+```java
+package io.eigr.spawn.test.actors;
+
+import io.eigr.spawn.api.actors.ActorContext;
+import io.eigr.spawn.api.actors.Value;
+import io.eigr.spawn.api.actors.annotations.Action;
+import io.eigr.spawn.api.actors.annotations.stateful.StatefulNamedActor;
+import io.eigr.spawn.api.extensions.DependencyInjector;
+import io.eigr.spawn.java.test.domain.Actor;
+
+@StatefulNamedActor(name = "test_actor_constructor", stateType = Actor.State.class)
+public final class ActorWithDependencies {
+
+    private final MessageService messageService;
+
+    public ActorWithConstructor(DependencyInjector injector) {
+       // Note how to use dependency injection here to get a concrete class of MessageService.
+        this.defaultMessage = injector.getInstance(MessageService.class);
+    }
+
+    @Action(inputType = Actor.Request.class)
+    public Value setLanguage(Actor.Request msg, ActorContext<Actor.State> context) {
+        if (context.getState().isPresent()) {
+        }
+
+        return Value.at()
+                .response(Actor.Reply.newBuilder()
+                        .setResponse(messageService.getDefaultMessage())
+                        .build())
+                .state(updateState("java"))
+                .reply();
+    }
+
+    private Actor.State updateState(String language) {
+        return Actor.State.newBuilder()
+                .addLanguages(language)
+                .build();
+    }
+}
+
+```
+
+3. Then you can pass your dependent classes this way to your Actor:
+```java
+package io.eigr.spawn.java.demo;
+
+import io.eigr.spawn.api.Spawn;
+import io.eigr.spawn.api.extensions.DependencyInjector;
+import io.eigr.spawn.api.extensions.SimpleDependencyInjector;
+
+public class App {
+   public static void main(String[] args) {
+      DependencyInjector injector = SimpleDependencyInjector.createInjector();
+      injector.bind(MessageService.class, new MessageServiceImpl());
+
+      Spawn spawnSystem = new Spawn.SpawnSystem()
+              .create("spawn-system")
+              .withActor(Joe.class, actorConstructorArgs, injector -> new Joe((DependencyInjector) injector))
+              .build();
+
+      spawnSystem.start();
+   }
+}
+```
+
+It is important to note that this helper mechanism does not currently implement any type of complex dependency graph. 
+Therefore, it will not build objects based on complex dependencies nor take care of the object lifecycle for you. 
+In other words, all instances added through the bind method of the SimpleDependencyInjector class will be singletons. 
+This mechanism works much more like a bucket of objects that will be forwarded via your actor's constructor.
+
 ### Types of Actors
 
 First we need to understand how the various types of actors available in Spawn behave. Spawn defines the following types of Actors:

pom.xml

@@ -4,7 +4,7 @@
     <groupId>io.eigr.spawn</groupId>
     <artifactId>spawn-java-std-sdk</artifactId>
     <packaging>jar</packaging>
-    <version>0.9.0</version>
+    <version>1.0.0</version>
     <name>spawn-java-std-sdk</name>
     <url>http://maven.apache.org</url>
 

src/main/java/io/eigr/spawn/api/ActorIdentity.java

@@ -14,7 +14,7 @@ public final class ActorIdentity {
     private ActorIdentity(String system, String name, String parent, boolean lookup){
         this.system = system;
         this.name = name;
-        this.maybeParent = Optional.ofNullable(parent);
+        this.maybeParent = Optional.of(parent);
         this.lookup = lookup;
     }
 
@@ -26,7 +26,7 @@ private ActorIdentity(String system, String name, boolean lookup){
     }
 
     public static ActorIdentity of(String system, String name) {
-        return new ActorIdentity(system, name, true);
+        return new ActorIdentity(system, name, false);
     }
 
     public static ActorIdentity of(String system, String name, String parent) {
@@ -58,6 +58,7 @@ public Optional<String> getMaybeParent() {
     }
 
     public boolean isParent() {
+        System.out.println(String.format("Actor %s is parent? = %s", this.name, this.maybeParent.isPresent()));
         return this.maybeParent.isPresent();
     }
 

src/main/java/io/eigr/spawn/api/ActorRef.java

@@ -43,10 +43,12 @@ protected static ActorRef of(SpawnClient client, Cache<ActorOuterClass.ActorId,
         ActorOuterClass.ActorId actorId;
 
         if (identity.isParent()) {
+            System.out.println("Passou como parent");
             actorId = buildActorId(identity.getSystem(), identity.getName(), identity.getParent());
 
             spawnActor(actorId, client);
         } else {
+            System.out.println("Passou como normal");
             actorId = buildActorId(identity.getSystem(), identity.getName());
         }
 
@@ -56,6 +58,7 @@ protected static ActorRef of(SpawnClient client, Cache<ActorOuterClass.ActorId,
         }
 
         if (identity.hasLookup()) {
+            System.out.println("Faca lookup");
             spawnActor(actorId, client);
         }
 

src/main/java/io/eigr/spawn/api/actors/ActorContext.java

@@ -1,15 +1,17 @@
 package io.eigr.spawn.api.actors;
 
 import io.eigr.spawn.api.Spawn;
+import io.eigr.spawn.api.extensions.DependencyInjector;
 
 import java.util.Optional;
 import java.util.StringJoiner;
 
 public final class ActorContext<S extends Object> {
     private Spawn spawn;
-
     private Optional<S> state;
 
+    private DependencyInjector injector;
+
     public ActorContext(Spawn spawn){
         this.spawn = spawn;
         this.state = Optional.empty();
@@ -28,6 +30,7 @@ public Optional<S> getState()  {
         return state;
     }
 
+
     @Override
     public String toString() {
         return new StringJoiner(", ", ActorContext.class.getSimpleName() + "[", "]")

src/main/java/io/eigr/spawn/api/extensions/DependencyInjector.java

@@ -0,0 +1,8 @@
+package io.eigr.spawn.api.extensions;
+
+public interface DependencyInjector {
+
+    <T extends Object> void bind(Class<T> type, Object instance);
+
+    <T extends Object> T getInstance(Class<T> type);
+}

src/main/java/io/eigr/spawn/api/extensions/SimpleDependencyInjector.java

@@ -0,0 +1,35 @@
+package io.eigr.spawn.api.extensions;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public final class SimpleDependencyInjector implements DependencyInjector {
+
+    private final Map<Class<?>, Object> bucket;
+
+    private SimpleDependencyInjector() {
+        this.bucket = new HashMap<>();
+    }
+
+    private static class SimpleDependencyInjectorHelper{
+        private static final SimpleDependencyInjector INSTANCE = new SimpleDependencyInjector();
+    }
+
+    public static DependencyInjector createInjector(){
+        return SimpleDependencyInjectorHelper.INSTANCE;
+    }
+
+    @Override
+    public <T> void bind(Class<T> type, Object instance) {
+        if (this.bucket.containsKey(type)) {
+            throw new IllegalArgumentException("There is already an instance associated with this type in the bucket");
+        }
+
+        this.bucket.put(type, instance);
+    }
+
+    @Override
+    public <T> T getInstance(Class<T> type) {
+        return type.cast(this.bucket.get(type));
+    }
+}

src/main/java/io/eigr/spawn/internal/transport/server/ActorServiceHandler.java

@@ -14,6 +14,7 @@
 import io.eigr.spawn.api.actors.ActorFactory;
 import io.eigr.spawn.api.actors.workflows.SideEffect;
 import io.eigr.spawn.api.exceptions.ActorInvocationException;
+import io.eigr.spawn.api.extensions.SimpleDependencyInjector;
 import io.eigr.spawn.internal.Entity;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

src/test/java/io/eigr/spawn/SpawnTest.java

@@ -6,6 +6,8 @@
 import io.eigr.spawn.api.TransportOpts;
 import io.eigr.spawn.api.exceptions.ActorCreationException;
 import io.eigr.spawn.api.exceptions.ActorInvocationException;
+import io.eigr.spawn.api.extensions.DependencyInjector;
+import io.eigr.spawn.api.extensions.SimpleDependencyInjector;
 import io.eigr.spawn.java.test.domain.Actor;
 import io.eigr.spawn.test.actors.ActorWithConstructor;
 import io.eigr.spawn.test.actors.JoeActor;
@@ -23,10 +25,13 @@ public class SpawnTest {
 
     @Before
     public void before() throws Exception {
+        DependencyInjector injector = SimpleDependencyInjector.createInjector();
+        injector.bind(String.class, "Hello with Constructor");
+
         spawnSystem = new Spawn.SpawnSystem()
                 .create("spawn-system")
                 .withActor(JoeActor.class)
-                .withActor(ActorWithConstructor.class, "Hello with Constructor", arg -> new ActorWithConstructor((String) arg))
+                .withActor(ActorWithConstructor.class, injector, arg -> new ActorWithConstructor((DependencyInjector) arg))
                 .withTransportOptions(
                         TransportOpts.builder()
                                 .port(8091)

src/test/java/io/eigr/spawn/test/actors/ActorWithConstructor.java

@@ -4,14 +4,16 @@
 import io.eigr.spawn.api.actors.Value;
 import io.eigr.spawn.api.actors.annotations.Action;
 import io.eigr.spawn.api.actors.annotations.stateful.StatefulNamedActor;
+import io.eigr.spawn.api.extensions.DependencyInjector;
 import io.eigr.spawn.java.test.domain.Actor;
 
 @StatefulNamedActor(name = "test_actor_constructor", stateType = Actor.State.class)
 public final class ActorWithConstructor {
+
     private final String defaultMessage;
 
-    public ActorWithConstructor(String defaultMessage) {
-        this.defaultMessage = defaultMessage;
+    public ActorWithConstructor(DependencyInjector injector) {
+        this.defaultMessage = injector.getInstance(String.class);
     }
 
     @Action(inputType = Actor.Request.class)