CompletableFuture support for java client

example/java/README.md

@@ -1,6 +1,6 @@
 # TDLib Java example
 
-To run this example, you will need installed JDK >= 1.6.
+To run this example, you will need installed JDK >= 1.8.
 For Javadoc documentation generation PHP is needed.
 
 You can find complete build instructions for your operating system at https://tdlib.github.io/td/build.html?language=Java.

example/java/org/drinkless/tdlib/Client.java

@@ -6,6 +6,7 @@
 //
 package org.drinkless.tdlib;
 
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -62,6 +63,30 @@ public interface LogMessageHandler {
         void onLogMessage(int verbosityLevel, String message);
     }
 
+    /**
+     * Result class for an asynchronous function call with a future response.
+     *
+     * @param <T> The object type that is returned by the function
+     */
+    public final static class Result<T extends TdApi.Object> {
+
+        /**
+         * An object of this type can be returned upon a successful function call, otherwise it will be null.
+         */
+        public final T object;
+
+        /**
+         * An object of this type can be returned on every function call, in case of an error, otherwise it will be null.
+         */
+        public final TdApi.Error error;
+
+        private Result(T object, TdApi.Error error) {
+            this.object = object;
+            this.error = error;
+        }
+
+    }
+
     /**
      * Exception class thrown when TDLib error occurred while performing {@link #execute(TdApi.Function)}.
      */
@@ -111,6 +136,27 @@ public void send(TdApi.Function query, ResultHandler resultHandler) {
         send(query, resultHandler, null);
     }
 
+    /**
+     * Sends a request to the TDLib.
+     *
+     * @param query Object representing a query to the TDLib.
+     * @param <T>   Automatically deduced return type of the query.
+     * @return      {@link CompletableFuture} response with {@link Result}
+     * If this stage completes exceptionally it throws {@link ExecutionException}
+     */
+    @SuppressWarnings("unchecked")
+    public <T extends TdApi.Object> CompletableFuture<Result<T>> send(TdApi.Function<T> query) {
+        CompletableFuture<Result<T>> future = new CompletableFuture<>();
+        send(query, object -> {
+            if (object instanceof TdApi.Error) {
+                future.complete(new Result<>(null, (TdApi.Error) object));
+            } else {
+                future.complete(new Result<>((T) object, null));
+            }
+        });
+        return future;
+    }
+
     /**
      * Synchronously executes a TDLib request. Only a few marked accordingly requests can be executed synchronously.
      *

example/java/td_jni.cpp

@@ -84,7 +84,7 @@ static jstring Function_toString(JNIEnv *env, jobject object) {
   return td::jni::to_jstring(env, to_string(td::td_api::Function::fetch(env, object)));
 }
 
-static constexpr jint JAVA_VERSION = JNI_VERSION_1_6;
+static constexpr jint JAVA_VERSION = JNI_VERSION_1_8;
 static JavaVM *java_vm;
 static jobject log_message_handler;