Add example

java/src/main/java/org/restrpc/examples/AsyncInvokeExample.java

@@ -0,0 +1,55 @@
+package org.restrpc.examples;
+
+import org.restrpc.client.AsyncRpcFunction;
+import org.restrpc.client.NativeRpcClient;
+import org.restrpc.client.RpcClient;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
+
+public class AsyncInvokeExample {
+
+    public static void main(String[] args) throws InterruptedException {
+        /**
+         * An example shows how we use this Java client to connect to
+         * the C++ RPC server and invoke the C++ RPC methods.
+         *
+         * First of all, we should run a C++ rpc server. In this example,
+         * we first run the `basic_server` which is written here:
+         * https://github.com/qicosmos/rest_rpc/blob/master/examples/server/main.cpp
+         *
+         * And make sure the C++ RPC server is listening on the address "127.0.0.1:9000".
+         *
+         * From the above C++ file, we can know that we registered the method `add()`:
+         *        int add(rpc_conn conn, int a, int b) {
+         * 		      return a + b;
+         *        }
+         *
+         * So we can create a Java RPC client to invoke that remote method by the following
+         * steps below.
+         */
+
+        // Create a RPC client instance.
+        RpcClient rpcClient = new NativeRpcClient();
+        // Connect to the C++ RPC server which is listening on `127.0.0.1:9000`.
+        rpcClient.connect("127.0.0.1:9000");
+        // Use `asyncFunc()` method as a proxy of the remote function. This can
+        // be known as a stub of the remote method.
+        AsyncRpcFunction remoteFunc = rpcClient.asyncFunc("add");
+        // The first argument indicates the return type you expected to return. It
+        // followed by the other arguments that the remote method takes to perform the
+        // `add()` method.
+        CompletableFuture<Object> future = remoteFunc.invoke(Integer.class, 100, 230);
+        // The last, we can use the future as async return value.
+        future.whenComplete((obj, exception) -> {
+            if (exception != null) {
+                System.out.println("Failed to invoke the add(100, 230) with: " + exception.getMessage());
+            } else {
+                System.out.println("The result of add(100, 230) is " + obj);
+            }
+        });
+        // You also get the return value synchronously:
+        //                Object result = future.get();
+        TimeUnit.SECONDS.sleep(10);
+    }
+}