Flutter接入移动解析HTTPDNS Android/iOS SDK实践方案

本文档介绍了在Flutter场景下移动解析HTTPDNS Android/iOS SDK的接入方式。

概述

Flutter是谷歌的移动UI框架，可以快速在iOS和Android上构建高质量的原生用户界面。 Flutter可以与现有的代码一起工作。在全世界，Flutter正在被越来越多的开发者和组织使用，并且Flutter是完全免费、开源的。Flutter使用Dart语言开发，有单独的Dart虚拟机，Dart可以被编译（AOT）成不同平台的本地代码，让Flutter可以直接和平台通讯而不需要一个中间的桥接过程，可见Flutter是一个高效的移动端跨平台框架。在实际的项目开发中主要有以下2种实践场景：

普通场景
整个Flutter项目全部由Dart实现，写一份代码可以运行在Android和iOS平台。
混合开发模式
整个Android/iOS项目是将Flutter作为module集成在项目中，通过MethodChannel实现两端的相互调用。

警告

由于Dart的底层HttpClient对外没有提供HTTPS的证书验证接口，通过Dart自带的HttpClient或使用第三方的Dio、Http网络框架，用户不能直接通过设置Host的IP直连方式进行HTTPS网络访问。因此要实现HTTPS的直连方案需要在本地搭建一个代理，在Socket建连的时候将用户访问的HOST替换成通过移动解析HTTPDNS SDK解析出的IP以实现HTTPS的IP直连访问。

Flutter场景下接入移动解析HTTPDNS Android、iOS端SDK实践完整代码请参考flutterDNSDemo源码。

实践方案

Flutter工程中Android端集成原生移动解析HTTPDNS SDK

在Android Studio中打开您的Flutter项目的Android部分：
启动 Android Studio，选择 File > Open…
定位到您 Flutter app目录, 然后选择里面的android文件夹，点击OK。在Java目录下打开MainActivity.java
在Application里集成移动解析HTTPDNS DNS Android SDK：
如何集成移动解析HTTPDNS DNS Android SDK请参考Android SDK开发指南文档。
在Android目录中定义和Flutter通信的MethodChannel：需要注意的是通道的名字要跟flutter的通道名称保持一致

package com.example.flutter;

import android.widget.Toast;
import com.alibaba.pdns.DNSResolver;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;
import io.flutter.embedding.android.FlutterActivity;
import android.content.Context;

public class MainActivity extends FlutterActivity {
    private MethodChannel channel;
    private Context context;

    //这个跟flutter的通道名称保持一直
    private static final String CHANNEL = "samples.flutter.io/getIP";
    //定义flutter端调用Android原生方法的channelMethod
    private static final String channelMethod = "getIP";
    //flutter对Android端的传参
    private static final String hostArgument = "host";
    //初始化阿里云公共DNS Android SDK中提供的DNSResolver对象
    private DNSResolver dnsResolver = null;

    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        //初始化DNSResolver
        dnsResolver = DNSResolver.getInstance();
        channel = new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL);
        channel.setMethodCallHandler(new MethodCallHandler() {
            @Override
            public void onMethodCall(MethodCall call, Result result) {
                //这里是判断是不是调getIP方法，因为所有的方法都走这里
                if (call.method.equals(channelMethod)) {
                    if (call.hasArgument(hostArgument)) {
                        try{
                            //取出从flutter端传递的host参数
                            String resolverName = call.argument(hostArgument);
                            String ip = dnsResolver.getIPV4ByHost(resolverName);
                            if (ip != null) {
                                result.success(ip);
                                Toast.makeText(MainActivity.this, "调用Android原生域名解析成功!", Toast.LENGTH_SHORT).show();
                            } else {
                                result.success(resolverName);
                            }
                        }catch (Exception e){
                            e.printStackTrace();
                        }
                    }
                }
            }
        });
    }
}

Flutter工程中iOS端集成原生移动解析HTTPDNS SDK

在Xcode中打开您的Flutter项目的iOS工程：
在Flutter项目中找到iOS目录下的Xcode工程文件，使用Xcode打开。
在Xcode工程里集成移动解析HTTPDNS iOS SDK：
如何集成移动解析HTTPDNS iOS SDK请参考iOS SDK开发指南文档。

在iOS中定义和Flutter通信的MethodChannel：

FlutterViewController* controller = (FlutterViewController*)self.window.rootViewController;
FlutterMethodChannel* getIPChannel = [FlutterMethodChannel
                                            methodChannelWithName:@"samples.flutter.io/getIP"
                                            binaryMessenger:controller];//跟flutter的通道名称保持一直
[getIPChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
        if ([@"getIP" isEqualToString:call.method]) {
            NSDictionary *argumentDic = call.arguments;
            result([self getIPWithHostName:argumentDic[@"host"]]); // 解析结果
        } else {
            result(FlutterMethodNotImplemented);
        }
}];

用户自定义获取域名解析结果IP的方法

- (NSString *)getIPWithHostName:(NSString *)hostName {//建议用户自行增加相应的容错处理，如果没有IP那么返回域名保证程序正常运行
    NSArray *array = [[DNSResolver share] getIpv4ByCacheWithDomain:hostName andExpiredIPEnabled:YES];
    if (array != NULL && array.count > 0) {
        return array[0];
    }else{
        return hostName;
    }
}

Flutter工程中通过methodChannel和自定义方法获取域名解析结果

static const platform = const MethodChannel('samples.flutter.io/getIP');
final String result = await platform.invokeMethod('getIP', {'host': '您要解析的域名'});

Flutter工程中HTTPS网络请求使用IP直连

void runPoxyRequest() async {
    var proxy = CustomHttpsProxy();
    final result = await proxy.init();
    print('proxy established： ${result != null}');
    await doHttpGet();
    proxy.close();
}
Future doHttpGet() async{
  var httpClient= HttpClient();
  httpClient.findProxy= (uri) => 'PROXY localhost:4041';
  var request= await httpClient.getUrl(Uri.parse('https://www.taobao.com'));
  var response= await request.close();
  //读取响应内容
  var responseBody= await response.transform(Utf8Decoder()).join();
  print(responseBody);
}

在Socket建连的时候将用户访问的HOST替换成IP以实现HTTPS的IP直连访问

import 'dart:io';
import 'dart:convert';

import 'package:flutter/services.dart';

class CustomHttpsProxy {
  final int port = 4041;
  ServerSocket? serverSocket;

  CustomHttpsProxy();

  Future init() async {
    await ServerSocket.bind(InternetAddress.anyIPv4, port).then((serverSocket) {
      this.serverSocket = serverSocket;
      serverSocket.listen((client) {
        try {
          ClientConnectionHandler(client).handle();
        } catch (e) {
          print('ClientConnectionHandler exception $e');
        }
      });
    }).catchError((e) {
      print('serverSocket 处理异常$e');
    });
    return serverSocket;
  }

  void close() {
    if (serverSocket != null) {
      serverSocket?.close();
    }
  }
}

class ClientConnectionHandler {
  final RegExp regx = RegExp(r'CONNECT ([^ :]+)(?::([0-9]+))? HTTP/1.1\r\n');
  static const platform = const MethodChannel('samples.flutter.io/getIP');
  Socket? server;
  Socket? client;
  String content = '';
  String host = '';
  int port = 443;

  ClientConnectionHandler(this.client);

  void closeSockets() {
//    print('socket is going to destroy');
    if (server != null) {
      server?.destroy();
    }
    client?.destroy();
  }

  Future<void> dataHandler(data) async {
    if (server == null) {
      content += utf8.decode(data);
      final m = regx.firstMatch(content);
      if (m != null) {
        host = m.group(1) ?? 'unknown';
        port = int.tryParse(m.group(2) ?? '') ?? 443;



        final String? resultIP = await platform.invokeMethod('getIP', {'host': host});
        final String realHost = resultIP ?? host;
        print('～～～～～$resultIP');
        try {
          ServerConnectionHandler(realHost, port, this)
              .handle()
              .catchError((e) {
            print('Server error $e');
            closeSockets();
          });
        } catch (e) {
          print('Server exception $e');
          closeSockets();
        }
      }
    } else {
      try {
        server?.add(data);
      } catch (e) {
        print('sever has been shut down');
        closeSockets();
      }
    }
  }

  void errorHandler(error, StackTrace trace) {
    print('client socket error: $error');
  }

  void doneHandler() {
    closeSockets();
  }

  void handle() {
    client?.listen(dataHandler,
        onError: errorHandler, onDone: doneHandler, cancelOnError: true);
  }
}

class ServerConnectionHandler {
  final String RESPONSE = 'HTTP/1.1 200 Connection Established\r\n\r\n';
  final String host;
  final int port;
  final ClientConnectionHandler handler;
  Socket? server;
  Socket? client;
  String content = '';

  ServerConnectionHandler(this.host, this.port, this.handler) {
    client = handler.client;
  }

  //接收报文
  void dataHandler(data) {
    try {
      client?.add(data);
    } on Exception catch (e) {
      print('client has been shut down $e');
      handler.closeSockets();
    }
  }

  void errorHandler(error, StackTrace trace) {
    print('server socket error: $error');
  }

  void doneHandler() {
    handler.closeSockets();
  }

  Future handle() async {
    print('尝试建立连接： $host:$port');
    server = await Socket.connect(host, port, timeout: Duration(seconds: 60));
    server?.listen(dataHandler,
        onError: errorHandler, onDone: doneHandler, cancelOnError: true);
    handler.server = server;
    client?.write(RESPONSE);
  }
}

说明

当前文档只针对Flutter场景下移动解析HTTPDNS Android/iOS SDK的使用。
开发者在Flutter场景下接入移动解析HTTPDNS Android/iOS SDK实践完整代码请参考flutterDNSDemo源码。