Implement abillity to handle Http-Requests asyncrounously

BlueMapCommon/src/main/java/de/bluecolored/bluemap/common/web/http/HttpConnection.java

@@ -6,18 +6,28 @@ import java.io.IOException;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
+import java.nio.channels.Channel;
 import java.nio.channels.SelectableChannel;
 import java.nio.channels.SelectionKey;
 import java.nio.channels.SocketChannel;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
 
 public class HttpConnection implements SelectionConsumer {
 
     private final HttpRequestHandler requestHandler;
+    private final Executor responseHandlerExecutor;
     private HttpRequest request;
+    private CompletableFuture<HttpResponse> futureResponse;
     private HttpResponse response;
 
     public HttpConnection(HttpRequestHandler requestHandler) {
+        this(requestHandler, Runnable::run); //run synchronously
+    }
+
+    public HttpConnection(HttpRequestHandler requestHandler, Executor responseHandlerExecutor) {
         this.requestHandler = requestHandler;
+        this.responseHandlerExecutor = responseHandlerExecutor;
     }
 
     @Override
@@ -48,10 +58,22 @@ public class HttpConnection implements SelectionConsumer {
             }
 
             // process request
-            if (response == null) {
-                this.response = requestHandler.handle(request);
+            if (futureResponse == null) {
+                futureResponse = CompletableFuture.supplyAsync(
+                        () -> requestHandler.handle(request),
+                        responseHandlerExecutor
+                );
+                futureResponse.thenAccept(response -> {
+                    try {
+                        response.read(channel); // do an initial read to trigger response sending intent
+                        this.response = response;
+                    } catch (IOException e) {
+                        handleIOException(channel, e);
+                    }
+                });
             }
 
+            if (response == null) return;
             if (!selectionKey.isValid()) return;
 
             // send response
@@ -63,16 +85,24 @@ public class HttpConnection implements SelectionConsumer {
             // reset to accept new request
             request.clear();
             response.close();
+            futureResponse = null;
             response = null;
             selectionKey.interestOps(SelectionKey.OP_READ);
 
         } catch (IOException e) {
-            Logger.global.logDebug("Failed to process selection: " + e);
-            try {
-                channel.close();
-            } catch (IOException e2) {
-                Logger.global.logWarning("Failed to close channel" + e2);
-            }
+            handleIOException(channel, e);
+        }
+    }
+
+    private void handleIOException(Channel channel, IOException e) {
+        request.clear();
+        response = null;
+
+        Logger.global.logDebug("Failed to process selection: " + e);
+        try {
+            channel.close();
+        } catch (IOException e2) {
+            Logger.global.logWarning("Failed to close channel" + e2);
         }
     }
 

BlueMapCommon/src/main/java/de/bluecolored/bluemap/common/web/http/HttpResponse.java

@@ -57,7 +57,7 @@ public class HttpResponse implements Closeable {
         this.headers = new HashMap<>();
     }
 
-    public boolean read(WritableByteChannel channel) throws IOException {
+    public synchronized boolean read(WritableByteChannel channel) throws IOException {
         if (complete) return true;
 
         // send headers

BlueMapCommon/src/main/java/de/bluecolored/bluemap/common/web/http/HttpServer.java

@@ -13,6 +13,10 @@ public class HttpServer extends Server {
     @Override
     public SelectionConsumer createConnectionHandler() {
         return new HttpConnection(requestHandler);
+
+        // Enable async request handling ...
+        // TODO: maybe find a better/separate executor than using bluemap's common thread-pool
+        //return new HttpConnection(requestHandler, BlueMap.THREAD_POOL);
     }
 
 }