前阵子有同学反馈Flutter中的http请求无法通过fiddler抓包,作者喜欢使用Charles抓包工具,于是抽时间写了个小demo测试了一下,结论是在手机上设置代理,Charles确实抓不到请求数据包。于是对该问题进行了分析:
http.dart中的HttpClient是一个抽象类,成员方法的具体实现在http_impl.dart中,http的get请求实现如下:
Future<HttpClientRequest> getUrl(Uri url) => _openUrl("get", url);
Future<_HttpClientRequest> _openUrl(String method, Uri uri) {
.
.
.
// Check to see if a proxy server should be used for this connection.
var proxyConf = const _ProxyConfiguration.direct();
if (_findProxy != null) {
// TODO(sgjesse): Keep a map of these as normally only a few
// configuration strings will be used.
try {
proxyConf = new _ProxyConfiguration(_findProxy(uri));
} catch (error, stackTrace) {
return new Future.error(error, stackTrace);
}
}
return _getConnection(uri.host, port, proxyConf, isSecure)
.then((_ConnectionInfo info) {
.
.
.
});
}
首先,我们可以发现方法中有一行注释// Check to see if a proxy server should be used for this connection.
,意思是“检查是否应该使用代理服务器进行此连接”;
然后,有一个proxyConf
对象初始化和根据_findProxy
来创建新的proxyConf对象的语句,然后通过_getConnection(uri.host, port, proxyConf, isSecure)
来创建连接,_getConnection的源码如下:
Future<_ConnectionInfo> _getConnection(String uriHost, int uriPort,
_ProxyConfiguration proxyConf, bool isSecure) {
Iterator<_Proxy> proxies = proxyConf.proxies.iterator;
Future<_ConnectionInfo> connect(error) {
if (!proxies.moveNext()) return new Future.error(error);
_Proxy proxy = proxies.current;
String host = proxy.isDirect ? uriHost : proxy.host;
int port = proxy.isDirect ? uriPort : proxy.port;
return _getConnectionTarget(host, port, isSecure)
.connect(uriHost, uriPort, proxy, this)
// On error, continue with next proxy.
.catchError(connect);
}
return connect(new HttpException("No proxies given"));
}
从代码中我们可以看到根据代理配置信息来将请求的host和port进行重置,然后创建真实的连接。
跟踪以上源码我们发现dart中http请求是否走代理是需要配置的,而_findProxy
变量和配置的代理信息有关。
http_impl.dart文件中的HttpClient类中定义了_findProxy
的默认值
Function _findProxy = HttpClient.findProxyFromEnvironment;
HttpClient类中findProxyFromEnvironment
方法的实现
static String findProxyFromEnvironment(Uri url,
{Map<String, String> environment}) {
HttpOverrides overrides = HttpOverrides.current;
if (overrides == null) {
return _HttpClient._findProxyFromEnvironment(url, environment);
}
return overrides.findProxyFromEnvironment(url, environment);
}
_HttpClient类中_findProxyFromEnvironment
方法的实现
static String _findProxyFromEnvironment(
Uri url, Map<String, String> environment) {
checkNoProxy(String option) {
if (option == null) return null;
Iterator<String> names = option.split(",").map((s) => s.trim()).iterator;
while (names.moveNext()) {
var name = names.current;
if ((name.startsWith("[") &&
name.endsWith("]") &&
"[${url.host}]" == name) ||
(name.isNotEmpty && url.host.endsWith(name))) {
return "DIRECT";
}
}
return null;
}
checkProxy(String option) {
if (option == null) return null;
option = option.trim();
if (option.isEmpty) return null;
int pos = option.indexOf("://");
if (pos >= 0) {
option = option.substring(pos + 3);
}
pos = option.indexOf("/");
if (pos >= 0) {
option = option.substring(0, pos);
}
// Add default port if no port configured.
if (option.indexOf("[") == 0) {
var pos = option.lastIndexOf(":");
if (option.indexOf("]") > pos) option = "$option:1080";
} else {
if (option.indexOf(":") == -1) option = "$option:1080";
}
return "PROXY $option";
}
// Default to using the process current environment.
if (environment == null) environment = _platformEnvironmentCache;
String proxyCfg;
String noProxy = environment["no_proxy"];
if (noProxy == null) noProxy = environment["NO_PROXY"];
if ((proxyCfg = checkNoProxy(noProxy)) != null) {
return proxyCfg;
}
if (url.scheme == "http") {
String proxy = environment["http_proxy"];
if (proxy == null) proxy = environment["HTTP_PROXY"];
if ((proxyCfg = checkProxy(proxy)) != null) {
return proxyCfg;
}
} else if (url.scheme == "https") {
String proxy = environment["https_proxy"];
if (proxy == null) proxy = environment["HTTPS_PROXY"];
if ((proxyCfg = checkProxy(proxy)) != null) {
return proxyCfg;
}
}
return "DIRECT";
}
从以上代码中可以发现代理配置从environment中读取,设置代理时必须指定http_proxy
或https_proxy
等。而从_openUrl方法实现中proxyConf = new _ProxyConfiguration(_findProxy(uri));
得出默认情况下environment是为空的,所以要想在Flutter的http请求中使用代理,则要指定相应的代理配置,即设置httpClient.findProxy
的值。
示例代码:
_getHttpData() async {
var httpClient = new HttpClient();
httpClient.findProxy = (url) {
return HttpClient.findProxyFromEnvironment(url, environment: {"http_proxy": 'http://192.168.124.7:8888',});
};
var uri =
new Uri.http('t.weather.sojson.com', '/api/weather/city/101210101');
var request = await httpClient.getUrl(uri);
var response = await request.close();
if (response.statusCode == 200) {
print('请求成功');
var responseBody = await response.transform(Utf8Decoder()).join();
print('responseBody = $responseBody');
} else {
print('请求失败');
}
}
以上代码设置后即可使用Fiddler或Charles抓包了。
注:
192.168.124.7
该IP为我们需要抓包的Charles所在电脑IP;如果使用Flutter写的APP不手动设置代理,则可以使用另一种方案来抓包。
通过电脑设置热点 -> 使用手机连接电脑热点上网 -> 在电脑上使用Wireshark抓数据包。
具体步骤如下(macOS系统下):
查看接口的IP地址
$ ping t.weather.sojson.com
PING nm.ctn.aicdn.com (58.222.18.24): 56 data bytes
64 bytes from 58.222.18.24: icmp_seq=0 ttl=54 time=16.792 ms
64 bytes from 58.222.18.24: icmp_seq=1 ttl=54 time=16.926 ms
64 bytes from 58.222.18.24: icmp_seq=2 ttl=54 time=15.804 ms
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