Selector + SocketChannel realization

task_2_1_2/app/build.gradle

@@ -24,6 +24,12 @@ dependencies {
 
     // This dependency is used by the application.
     implementation libs.guava
+
+    compileOnly 'org.projectlombok:lombok:1.18.32'
+	annotationProcessor 'org.projectlombok:lombok:1.18.32'
+
+	testCompileOnly 'org.projectlombok:lombok:1.18.32'
+	testAnnotationProcessor 'org.projectlombok:lombok:1.18.32'
 }
 
 // Apply a specific Java toolchain to ease working on different environments.

task_2_1_2/app/src/main/java/org/prime/Message.java

@@ -1,20 +1,12 @@
 package org.prime;
 
 import java.io.Serializable;
-import java.util.ArrayList;
+import java.util.List;
 
-class Message implements Serializable {
-    private ArrayList<Integer> numbers;
+import lombok.Data;
 
-    public Message(int count) {
-        numbers = new ArrayList<>();
-        final int prime = 1000000007;
-        for (int i = 0; i < count; i++) {
-            numbers.add(prime);
-        }
-    }
-
-    public ArrayList<Integer> getNumbers() {
-        return numbers;
-    }
+@Data
+public class Message implements Serializable {
+    private String type;
+    private List<Integer> data;
 }

task_2_1_2/app/src/main/java/org/prime/PrimeClient.java

@@ -0,0 +1,117 @@
+package org.prime;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.net.InetSocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.SocketChannel;
+import java.util.ArrayList;
+import java.util.List;
+
+public class PrimeClient {
+    private SocketChannel socket;
+    private ByteBuffer buffer;
+
+    public PrimeClient(String address, int port) throws IOException {
+        socket = SocketChannel.open(new InetSocketAddress(address, port));
+        System.out.println("Chanell binded on ip " + address + " on port " + port);
+        socket.configureBlocking(false);
+        System.out.println("Chanell configured");
+        buffer = ByteBuffer.allocate(256);
+    }
+
+    public void start() throws IOException {
+        // ready to work notification to server
+        sendMessage(createMessage("REQUEST", null));
+
+        int requestAttempts = 0;
+
+        while (true) {
+            buffer.clear();
+            int bytesRead = socket.read(buffer);
+            if (bytesRead == -1) {
+                System.out.println("Server is down. Shutting down...");
+                return;
+            }
+            if (bytesRead > 0) {
+                buffer.flip();
+                try {
+                    Message message = readMessageFromBuffer();
+                    String messageType = message.getType();
+                    switch (messageType) {
+                        case "TASK":
+                            handleTask(message.getData());
+                            requestAttempts = 0;
+                            break;
+                        case "EXIT":
+                            System.out.println("Tasks done. Exiting program...");
+                            return;
+                        default:
+                            System.out.println("Unknown message type. Syncronize types with server");
+                            break;
+                    }
+                } catch (ClassNotFoundException e) {
+                    if (requestAttempts >= 3) {
+                        System.out.println("Too many attempts to receive message. Aborting...");
+                        return;
+                    }
+                    System.out.println("Error to cast received message from server to Message class.");
+                    System.out.println("Requesting task.");
+                    sendMessage(createMessage("REQUEST", null));
+                    requestAttempts++;
+                }
+                buffer.clear();
+            }
+        }
+    }
+
+    private void handleTask(List<Integer> nums) throws IOException {
+        for (Integer number : nums) {
+            if (!isPrime(number)) {
+                sendMessage(createMessage("RESULT", null));
+                return;
+            }
+        }
+        sendMessage(createMessage("RESULT", new ArrayList<>()));
+    }
+
+    private boolean isPrime(int number) {
+        if (number <= 1) return false;
+        for (int i = 2; i <= Math.sqrt(number); i++) {
+            if (number % i == 0) return false;
+        }
+        return true;
+    }
+
+    private Message createMessage(String type, List<Integer> data) {
+        Message message = new Message();
+        message.setType(type);
+        message.setData(data);
+        return message;
+    }
+
+    private Message readMessageFromBuffer() throws IOException, ClassNotFoundException {
+        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(buffer.array());
+        ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
+        Message message = (Message) objectInputStream.readObject();
+        return message;
+    }
+
+    private void sendMessage(Message message) throws IOException {
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
+        objectOutputStream.writeObject(message);
+        objectOutputStream.flush();
+        byte[] data = byteArrayOutputStream.toByteArray();
+        ByteBuffer buffer = ByteBuffer.wrap(data);
+        socket.write(buffer);
+    }
+
+    public static void main(String[] args) throws IOException {
+        PrimeClient client = new PrimeClient("localhost", 5000);
+        client.start();
+    }
+}