JavaClient can stream the HTTP response body (dart-lang#1005)

Author: alex-james-dev

pkgs/java_http/lib/src/java_client.dart

@@ -2,10 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:typed_data';
 
+import 'package:async/async.dart';
 import 'package:http/http.dart';
 import 'package:jni/jni.dart';
 import 'package:path/path.dart';
@@ -39,51 +41,118 @@ class JavaClient extends BaseClient {
     // See https://github.com/dart-lang/http/pull/980#discussion_r1253700470.
     _initJVM();
 
+    final receivePort = ReceivePort();
+    final events = StreamQueue<dynamic>(receivePort);
+
     // We can't send a StreamedRequest to another Isolate.
     // But we can send Map<String, String>, String, UInt8List, Uri.
-    final requestBody = await request.finalize().toBytes();
-    final requestHeaders = request.headers;
-    final requestMethod = request.method;
-    final requestUrl = request.url;
-
-    final (statusCode, reasonPhrase, responseHeaders, responseBody) =
-        await Isolate.run(() async {
-      final httpUrlConnection = URL
-          .ctor3(requestUrl.toString().toJString())
-          .openConnection()
-          .castTo(HttpURLConnection.type, deleteOriginal: true);
-
-      requestHeaders.forEach((headerName, headerValue) {
-        httpUrlConnection.setRequestProperty(
-            headerName.toJString(), headerValue.toJString());
-      });
-
-      httpUrlConnection.setRequestMethod(requestMethod.toJString());
-      _setRequestBody(httpUrlConnection, requestBody);
-
-      final statusCode = _statusCode(requestUrl, httpUrlConnection);
-      final reasonPhrase = _reasonPhrase(httpUrlConnection);
-      final responseHeaders = _responseHeaders(httpUrlConnection);
-      final responseBody = _responseBody(httpUrlConnection);
-
-      httpUrlConnection.disconnect();
+    final isolateRequest = (
+      sendPort: receivePort.sendPort,
+      url: request.url,
+      method: request.method,
+      headers: request.headers,
+      body: await request.finalize().toBytes(),
+    );
+
+    // Could create a new class to hold the data for the isolate instead
+    // of using a record.
+    await Isolate.spawn(_isolateMethod, isolateRequest);
+
+    final statusCodeEvent = await events.next;
+    late int statusCode;
+    if (statusCodeEvent is ClientException) {
+      // Do we need to close the ReceivePort here as well?
+      receivePort.close();
+      throw statusCodeEvent;
+    } else {
+      statusCode = statusCodeEvent as int;
+    }
 
-      return (
-        statusCode,
-        reasonPhrase,
-        responseHeaders,
-        responseBody,
-      );
-    });
+    final reasonPhrase = await events.next as String?;
+    final responseHeaders = await events.next as Map<String, String>;
+
+    Stream<List<int>> responseBodyStream(Stream<dynamic> events) async* {
+      try {
+        await for (final event in events) {
+          if (event is List<int>) {
+            yield event;
+          } else if (event is ClientException) {
+            throw event;
+          } else if (event == null) {
+            return;
+          }
+        }
+      } finally {
+        // TODO: Should we kill the isolate here?
+        receivePort.close();
+      }
+    }
 
-    return StreamedResponse(Stream.value(responseBody), statusCode,
-        contentLength:
-            _contentLengthHeader(request, responseHeaders, responseBody.length),
+    return StreamedResponse(responseBodyStream(events.rest), statusCode,
+        contentLength: _parseContentLengthHeader(request.url, responseHeaders),
         request: request,
         headers: responseHeaders,
         reasonPhrase: reasonPhrase);
   }
 
+  // TODO: Rename _isolateMethod to something more descriptive.
+  void _isolateMethod(
+    ({
+      SendPort sendPort,
+      Uint8List body,
+      Map<String, String> headers,
+      String method,
+      Uri url,
+    }) request,
+  ) {
+    final httpUrlConnection = URL
+        .ctor3(request.url.toString().toJString())
+        .openConnection()
+        .castTo(HttpURLConnection.type, deleteOriginal: true);
+
+    request.headers.forEach((headerName, headerValue) {
+      httpUrlConnection.setRequestProperty(
+          headerName.toJString(), headerValue.toJString());
+    });
+
+    httpUrlConnection.setRequestMethod(request.method.toJString());
+    _setRequestBody(httpUrlConnection, request.body);
+
+    try {
+      final statusCode = _statusCode(request.url, httpUrlConnection);
+      request.sendPort.send(statusCode);
+    } on ClientException catch (e) {
+      request.sendPort.send(e);
+      httpUrlConnection.disconnect();
+      return;
+    }
+
+    final reasonPhrase = _reasonPhrase(httpUrlConnection);
+    request.sendPort.send(reasonPhrase);
+
+    final responseHeaders = _responseHeaders(httpUrlConnection);
+    request.sendPort.send(responseHeaders);
+
+    // TODO: Throws a ClientException if the content length header is invalid.
+    // I think we need to send the ClientException over the SendPort.
+    final contentLengthHeader = _parseContentLengthHeader(
+      request.url,
+      responseHeaders,
+    );
+
+    _responseBody(
+      request.url,
+      httpUrlConnection,
+      request.sendPort,
+      contentLengthHeader,
+    );
+
+    httpUrlConnection.disconnect();
+
+    // Signals to the receiving isolate that we are done sending events.
+    request.sendPort.send(null);
+  }
+
   void _setRequestBody(
     HttpURLConnection httpUrlConnection,
     Uint8List requestBody,
@@ -142,42 +211,50 @@ class JavaClient extends BaseClient {
     return headers.map((key, value) => MapEntry(key, value.join(',')));
   }
 
-  int? _contentLengthHeader(
-      BaseRequest request, Map<String, String> headers, int bodyLength) {
+  int? _parseContentLengthHeader(
+    Uri requestUrl,
+    Map<String, String> headers,
+  ) {
     int? contentLength;
     switch (headers['content-length']) {
       case final contentLengthHeader?
           when !_digitRegex.hasMatch(contentLengthHeader):
         throw ClientException(
           'Invalid content-length header [$contentLengthHeader].',
-          request.url,
+          requestUrl,
         );
       case final contentLengthHeader?:
         contentLength = int.parse(contentLengthHeader);
-        if (bodyLength < contentLength) {
-          throw ClientException('Unexpected end of body', request.url);
-        }
     }
 
     return contentLength;
   }
 
-  Uint8List _responseBody(HttpURLConnection httpUrlConnection) {
+  void _responseBody(
+    Uri requestUrl,
+    HttpURLConnection httpUrlConnection,
+    SendPort sendPort,
+    int? expectedBodyLength,
+  ) {
     final responseCode = httpUrlConnection.getResponseCode();
 
     final inputStream = (responseCode >= 200 && responseCode <= 299)
         ? httpUrlConnection.getInputStream()
         : httpUrlConnection.getErrorStream();
 
-    final bytes = <int>[];
     int byte;
+    var actualBodyLength = 0;
+    // TODO: inputStream.read() could throw IOException.
     while ((byte = inputStream.read()) != -1) {
-      bytes.add(byte);
+      sendPort.send([byte]);
+      actualBodyLength++;
     }
 
-    inputStream.close();
+    if (expectedBodyLength != null && actualBodyLength < expectedBodyLength) {
+      sendPort.send(ClientException('Unexpected end of body', requestUrl));
+    }
 
-    return Uint8List.fromList(bytes);
+    inputStream.close();
   }
 }
 

pkgs/java_http/pubspec.yaml

@@ -8,6 +8,7 @@ environment:
   sdk: ^3.0.0
 
 dependencies:
+  async: ^2.11.0
   http: '>=0.13.4 <2.0.0'
   jni: ^0.5.0
   path: ^1.8.0

pkgs/java_http/test/java_client_test.dart

@@ -9,7 +9,8 @@ import 'package:test/test.dart';
 void main() {
   group('java_http client conformance tests', () {
     testIsolate(JavaClient.new);
-    testResponseBody(JavaClient(), canStreamResponseBody: false);
+    testResponseBody(JavaClient());
+    testResponseBodyStreamed(JavaClient());
     testResponseHeaders(JavaClient());
     testRequestBody(JavaClient());
     testRequestHeaders(JavaClient());