关于WKWebView的post请求丢失body问题的处理方案

WKWebView的优点这里不做过多详情，主要说一下最近处理WKWebView的post请求丢失body问题的处理方案。
WKWebView 通过loadrequest方法加载Post请求会丢失请求体（body）中的内容，进而导致服务器拿不到body中的内容的问题的发生。这个问题的产生主要是由于WKWebView的网络请求的进程与APP不是同一个进程，所以网络请求的过程是这样的：
由APP所在的进程发起request，而后通过IPC通信(进程间通信)将请求的相关信息（请求头、请求行、请求体等）传递给webkit网络线进程接收包装，进行数据的HTTP请求，最终再进行IPC的通信回传给APP所在的进程的。这里假如发起的request请求是post请求的话，因为要进行IPC数据传递，传递的请求体body中根据系统调度，将其舍弃，最终在WKWebView网络进程接受的时候请求体body中的内容变成了空，导致此种情况下的服务器获取不到请求体，导致问题的产生。
为了能够获取POST方法请求之后的body内容，这两天整理了少量处理方案，大致分为三种：

1.将网络请求交由Js发起，绕开系统WKWebView的网络的进程请求达到正常请求的目的
2.改变POST请求的方法为GET方法(有风险，不肯定服务器会接受GET方法)
3.将Post请求的请求body内容放入请求的Header中，并通过URLProtocol阻拦自己设置协议，在阻拦中通过NSConnection进行重新请求（重新包装请求body），而后通过回调Client用户端来传递数据内容

三种方法中，我采用了第三种方案，这里说一下第三种方案的实现方式，大致分为三步:

1.注册阻拦的自己设置的scheme
2.重写loadRequest()方法，根据request的method方法能否为POST进行URL的阻拦替换
3.在URLProtocol中进行request的重新包装（获取请求的body内容），使用NSURLConnection进行HTTP请求并将数据回传
这里说明一下为什么要自己去注册自己设置的scheme，而不是直接阻拦https/http。主要起因是：假如注册了https/http的阻拦，那么所有的http(s)请求都会交由系统进程解决，那么此时系统进程会通过IPC的形式传递给实现URLProctol协议的类去解决，在通过IPC传递的过程中丢失body体（上面有讲到），所以在阻拦的时候是拿不到POST方法的请求体body的。然而并不是所有的http请求都会走loadrequest（）方法（比方js中的ajax请求），所以导致少量POST请求没有被包装（将请求体body内容放到请求头header）就被阻拦了，进而丢失请求体body内容，问题一样会产生。所以为了避免这样的问题，我们需要自己去定一个scheme协议，保证不过度阻拦并且能够解决我们需要解决的POST请求内容。

以下是具体的实现方式：

1.注册阻拦的自己设置的scheme

    [NSURLProtocol registerClass:NSClassFromString(@“GCURLProtocol")];    [NSURLProtocol wk_registerScheme:@"gc"];    [NSURLProtocol wk_registerScheme:WkCustomHttp];    [NSURLProtocol wk_registerScheme:WkCustomHttps];

2.重写loadRequest()方法，根据request的method方法能否为POST进行URL的阻拦替换

//包装请求头内容- (WKNavigation *)loadRequest:(NSURLRequest *)request{    NSLog(@"发起请求:%@ method:%@",request.URL.absoluteString,request.HTTPMethod);    NSMutableURLRequest *mutableRequest = [request mutableCopy];    NSMutableDictionary *requestHeaders = [request.allHTTPHeaderFields mutableCopy];    //判断能否是POST请求，POST请求需要包装request中的body内容到请求头中（会有丢失body问题的产生）    //,包装完成之后重定向到阻拦的协议中自己包装解决请求数据内容，阻拦协议是GCURLProtocol，请自行搜索    if ([mutableRequest.HTTPMethod isEqualToString:@"POST"] && ([mutableRequest.URL.scheme isEqualToString:@"http"] || [mutableRequest.URL.scheme isEqualToString:@"https"])) {        NSString *absoluteStr = mutableRequest.URL.absoluteString;        if ([[absoluteStr substringWithRange:NSMakeRange(absoluteStr.length-1, 1)] isEqualToString:@"/"]) {            absoluteStr = [absoluteStr stringByReplacingCharactersInRange:NSMakeRange(absoluteStr.length-1, 1) withString:@""];        }                if ([mutableRequest.URL.scheme isEqualToString:@"https"]) {            absoluteStr = [absoluteStr stringByReplacingOccurrencesOfString:@"https" withString:WkCustomHttps];        }else{            absoluteStr = [absoluteStr stringByReplacingOccurrencesOfString:@"http" withString:WkCustomHttp];        }                mutableRequest.URL = [NSURL URLWithString:absoluteStr];        NSString *bodyDataStr = [[NSString alloc]initWithData:mutableRequest.HTTPBody encoding:NSUTF8StringEncoding];        [requestHeaders addEntriesFromDictionary:@{@"httpbody":bodyDataStr}];        mutableRequest.allHTTPHeaderFields = requestHeaders;                NSLog(@"当前请求为POST请求Header:%@",mutableRequest.allHTTPHeaderFields);            }    return [super loadRequest:mutableRequest];}

3.在URLProtocol中进行request的重新包装（获取请求的body内容），使用NSURLConnection进行HTTP请求并将数据回传（以下是主要代码）

+ (BOOL)canInitWithRequest:(NSURLRequest *)request {        NSString *scheme = request.URL.scheme;        if ([scheme isEqualToString:InterceptionSchemeKey]){                if ([self propertyForKey:HaveDealRequest inRequest:request]) {            NSLog(@"已经解决，放行");            return NO;        }        return YES;    }        if ([scheme isEqualToString:WkCustomHttp]){                      if ([self propertyForKey:HaveDealWkHttpPostBody inRequest:request]) {               NSLog(@"已经解决，放行");               return NO;           }           return YES;       }        if ([scheme isEqualToString:WkCustomHttps]){                if ([self propertyForKey:HaveDealWkHttpsPostBody inRequest:request]) {            NSLog(@"已经解决，放行");            return NO;        }        return YES;    }            return NO;    }- (void)startLoading {        //截获 gc 链接的所有请求，替换成本地资源或者者线上资源    if ([self.request.URL.scheme isEqualToString:InterceptionSchemeKey]) {        [self htmlCacheRequstLoad];    }        else if ([self.request.URL.scheme isEqualToString:WkCustomHttp] || [self.request.URL.scheme isEqualToString:WkCustomHttps]){        [self postBodyAddLoad];    }    else{        NSMutableURLRequest *newRequest = [self cloneRequest:self.request];        NSString *urlString = newRequest.URL.absoluteString;        [self addHttpPostBody:newRequest];        [NSURLProtocol setProperty:@YES forKey:GCProtocolKey inRequest:newRequest];        [self sendRequest:newRequest];    }       }- (void)addHttpPostBody:(NSMutableURLRequest *)redirectRequest{        //判断当前的请求能否是Post请求    if ([self.request.HTTPMethod isEqualToString:@"POST"]) {        NSLog(@"post请求");        NSMutableDictionary *headerDict = [redirectRequest.allHTTPHeaderFields mutableCopy];        NSString *body = headerDict[@"httpbody"]?:@"";        if (body.length) {            redirectRequest.HTTPBody = [body dataUsingEncoding:NSUTF8StringEncoding];            NSLog(@"body:%@",body);        }    }}- (void)postBodyAddLoad{        NSMutableURLRequest *cloneRequest = [self cloneRequest:self.request];    if ([cloneRequest.URL.scheme isEqualToString:WkCustomHttps]) {        cloneRequest.URL = [NSURL URLWithString:[cloneRequest.URL.absoluteString stringByReplacingOccurrencesOfString:WkCustomHttps withString:@"https"]];        [NSURLProtocol setProperty:@YES forKey:HaveDealWkHttpsPostBody inRequest:cloneRequest];    }else if ([cloneRequest.URL.scheme isEqualToString:WkCustomHttp]){                cloneRequest.URL = [NSURL URLWithString:[cloneRequest.URL.absoluteString stringByReplacingOccurrencesOfString:WkCustomHttp withString:@"http"]];        [NSURLProtocol setProperty:@YES forKey:HaveDealWkHttpPostBody inRequest:cloneRequest];    }    //增加body内容    [self addHttpPostBody:cloneRequest];    NSLog(@"请求body增加完成:%@",[[NSString alloc]initWithData:cloneRequest.HTTPBody encoding:NSUTF8StringEncoding]);    [self sendRequest:cloneRequest];    }//复制Request对象- (NSMutableURLRequest *)cloneRequest:(NSURLRequest *)request{    NSMutableURLRequest *newRequest = [NSMutableURLRequest requestWithURL:request.URL cachePolicy:request.cachePolicy timeoutInterval:request.timeoutInterval];        newRequest.allHTTPHeaderFields = request.allHTTPHeaderFields;    [newRequest setValue:@"image/webp,image/*;q=0.8" forHTTPHeaderField:@"Accept"];        if (request.HTTPMethod) {        newRequest.HTTPMethod = request.HTTPMethod;    }        if (request.HTTPBodyStream) {        newRequest.HTTPBodyStream = request.HTTPBodyStream;    }        if (request.HTTPBody) {        newRequest.HTTPBody = request.HTTPBody;    }        newRequest.HTTPShouldUsePipelining = request.HTTPShouldUsePipelining;    newRequest.mainDocumentURL = request.mainDocumentURL;    newRequest.networkServiceType = request.networkServiceType;        return newRequest;}#pragma mark - NSURLConnectionDataDelegate- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    /**     * 收到服务器响应     */    NSURLResponse *returnResponse = response;    [self.client URLProtocol:self didReceiveResponse:returnResponse cacheStoragePolicy:NSURLCacheStorageAllowed];}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    /**     * 接收数据     */    if (!self.recData) {        self.recData = [NSMutableData new];    }    if (data) {        [self.recData appendData:data];    }}- (nullable NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(nullable NSURLResponse *)response{    /**     * 重定向     */    if (response) {        [self.client URLProtocol:self wasRedirectedToRequest:request redirectResponse:response];    }    return request;}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{    [self.client URLProtocolDidFinishLoading:self];}- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    /**     * 加载失败     */    [self.client URLProtocol:self didFailWithError:error];}