Add FCM request improvements

components/device-mgt-extensions/io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provider.fcm/pom.xml

@@ -151,6 +151,10 @@
             <groupId>org.wso2.carbon</groupId>
             <artifactId>org.wso2.carbon.utils</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.squareup.okhttp3</groupId>
+            <artifactId>okhttp</artifactId>
+        </dependency>
     </dependencies>
 
     <build>

components/device-mgt-extensions/io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provider.fcm/src/main/java/io/entgra/device/mgt/core/device/mgt/extensions/push/notification/provider/fcm/FCMNotificationStrategy.java

@@ -19,6 +19,9 @@ package io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provid
 
 import com.google.gson.JsonObject;
 import io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provider.fcm.util.FCMUtil;
+import okhttp3.Request;
+import okhttp3.RequestBody;
+import okhttp3.Response;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import io.entgra.device.mgt.core.device.mgt.common.Device;
@@ -89,8 +92,6 @@ public class FCMNotificationStrategy implements NotificationStrategy {
      */
     private void sendWakeUpCall(String accessToken, String registrationId) throws IOException,
             PushNotificationExecutionFailedException {
-        HttpURLConnection conn = null;
-
         String fcmServerEndpoint = FCMUtil.getInstance().getContextMetadataProperties()
                 .getProperty(FCM_ENDPOINT_KEY);
         if(fcmServerEndpoint == null) {
@@ -99,26 +100,21 @@ public class FCMNotificationStrategy implements NotificationStrategy {
             throw new PushNotificationExecutionFailedException(msg);
         }
 
-        try {
-            byte[] bytes = getFCMRequest(registrationId).getBytes();
-            URL url = new URL(fcmServerEndpoint);
-            conn = (HttpURLConnection) url.openConnection();
-            conn.setRequestProperty("Content-Type", "application/json");
-            conn.setRequestProperty("Authorization", "Bearer " + accessToken);
-            conn.setRequestMethod("POST");
-            conn.setDoOutput(true);
-
-            try (OutputStream os = conn.getOutputStream()) {
-                os.write(bytes);
-            }
-
-            int status = conn.getResponseCode();
-            if (status != 200) {
-                log.error("Response Status: " + status + ", Response Message: " + conn.getResponseMessage());
+        RequestBody fcmRequest = getFCMRequest(registrationId);
+        Request request = new Request.Builder()
+                .url(fcmServerEndpoint)
+                .post(fcmRequest)
+                .addHeader("Authorization", "Bearer " + accessToken)
+                .build();
+        try (Response response = FCMUtil.getInstance().getHttpClient().newCall(request).execute()) {
+            if (log.isDebugEnabled()) {
+                log.debug("FCM message sent to the FCM server. Response code: " + response.code()
+                        + " Response message : " + response.message());
             }
-        } finally {
-            if (conn != null) {
-                conn.disconnect();
+            if(!response.isSuccessful()) {
+                String msg = "Response Status: " + response.code() + ", Response Message: " + response.message();
+                log.error(msg);
+                throw new IOException(msg);
             }
         }
     }
@@ -128,14 +124,14 @@ public class FCMNotificationStrategy implements NotificationStrategy {
      * @param registrationId Registration ID of the device
      * @return FCM request as a JSON string
      */
-    private static String getFCMRequest(String registrationId) {
+    private static RequestBody getFCMRequest(String registrationId) {
         JsonObject messageObject = new JsonObject();
         messageObject.addProperty("token", registrationId);
 
         JsonObject fcmRequest = new JsonObject();
         fcmRequest.add("message", messageObject);
 
-        return fcmRequest.toString();
+        return RequestBody.create(fcmRequest.toString(), okhttp3.MediaType.parse("application/json"));
     }
 
     @Override

components/device-mgt-extensions/io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provider.fcm/src/main/java/io/entgra/device/mgt/core/device/mgt/extensions/push/notification/provider/fcm/util/FCMUtil.java

@@ -22,6 +22,8 @@ import io.entgra.device.mgt.core.device.mgt.core.config.DeviceConfigurationManag
 import io.entgra.device.mgt.core.device.mgt.core.config.push.notification.ContextMetadata;
 import io.entgra.device.mgt.core.device.mgt.core.config.push.notification.PushNotificationConfiguration;
 import io.entgra.device.mgt.core.device.mgt.extensions.push.notification.provider.fcm.FCMNotificationStrategy;
+import okhttp3.ConnectionPool;
+import okhttp3.OkHttpClient;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.wso2.carbon.utils.CarbonUtils;
@@ -33,6 +35,7 @@ import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.List;
 import java.util.Properties;
+import java.util.concurrent.TimeUnit;
 
 public class FCMUtil {
 
@@ -43,10 +46,29 @@ public class FCMUtil {
             "repository" + File.separator + "resources" + File.separator + "service-account.json";
     private static final String[] FCM_SCOPES = { "https://www.googleapis.com/auth/firebase.messaging" };
     private Properties contextMetadataProperties;
+    private static ConnectionPool connectionPool;
+    private static OkHttpClient client;
 
     private FCMUtil() {
         initContextConfigs();
         initDefaultOAuthApplication();
+        initPooledConnection();
+    }
+
+    /**
+     * Initialize the connection pool for the OkHttpClient instance.
+     */
+    private void initPooledConnection() {
+        connectionPool = new ConnectionPool(25, 1, TimeUnit.MINUTES);
+        client = new OkHttpClient.Builder().connectionPool(connectionPool).build();
+    }
+
+    /**
+     * Get the Pooled OkHttpClient instance
+     * @return OkHttpClient instance
+     */
+    public OkHttpClient getHttpClient() {
+        return client;
     }
 
     private void initDefaultOAuthApplication() {