WKWebView的请求拦截和修改实现。技术方法：NSURLProtocol

需求，拦截WKWebview中的所有网络请求，并且对亲够Request的httpheader中添加字段token，等信息。
实现技术，利用NSURLProtocol。
首先实现一个继承自NSURLProtocol的自定义类：MYSchemeURLProtocol,完整的代码实现如下：

//类文件

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

#define MYSchemeURLHeaderTokenAdd 0

FOUNDATION_EXTERN NSString *const URLLoadingNotification;

FOUNDATION_EXTERN NSString *const HttpProtocolKey;
FOUNDATION_EXTERN NSString *const HttpsProtocolKey;

@interface MYSchemeURLProtocol : NSURLProtocol
- (void)registSchemeURLProtocol;
- (void)unregistSchemeURLProtocol;
  @end
@interface NSMutableURLRequest (MYHeaderAppend)
- (BOOL)appendRemoteAccessHeaders;
  @end
NS_ASSUME_NONNULL_END

//================.m ===================
#import "MYSchemeURLProtocol.h"
#import "JSON.h"

NSString *const URLLoadingNotification = @"com.zspace.urlLoadingNotification";
static NSString *kURLProtocolHandledKey = @"URLProtocolHandledKey";
NSString *const HttpProtocolKey = @"http";
NSString *const HttpsProtocolKey = @"https";

@interface MYSchemeURLProtocol()<NSURLSessionDelegate>

@property (atomic,strong,readwrite) NSURLSessionDataTask *task;
@property (nonatomic,strong) NSURLSession *session;
@property (nonatomic, strong) NSOperationQueue *queue;

@end

@implementation MYSchemeURLProtocol
- (void)registSchemeURLProtocol {
  // 防止苹果静态检查将 WKBrowsingContextController 拆分，然后再拼凑起来
  NSArray *privateStrArr = @[@"Controller", @"Context", @"Browsing", @"K", @"W"];
  NSString *className = [[[privateStrArr reverseObjectEnumerator] allObjects] componentsJoinedByString:@""];
  Class cls = NSClassFromString(className);
  SEL sel = NSSelectorFromString(@"registerSchemeForCustomProtocol:");
  
  if (cls && sel) {
  if ([(id)cls respondsToSelector:sel]) {
  #pragma clang diagnostic push
  #pragma clang diagnostic ignored "-Warc-performSelector-leaks"
  // 注册自定义协议
  // [(id)cls performSelector:sel withObject:@"CustomProtocol"];
  // 注册http协议
  [(id)cls performSelector:sel withObject:HttpProtocolKey];
  // 注册https协议
  // [(id)cls performSelector:sel withObject:HttpsProtocolKey];
  #pragma clang diagnostic pop
  }
  }
  // SechemaURLProtocol 自定义类继承于 NSURLProtocol
  [NSURLProtocol registerClass:[MYSchemeURLProtocol class]];
  }
- (void)unregistSchemeURLProtocol {
  [NSURLProtocol unregisterClass:[MYSchemeURLProtocol class]];
  }
- (BOOL)canInitWithRequest:(NSURLRequest )request
  {
  NSString scheme = [[request URL] scheme];
  // 判断是否需要进入自定义加载器
  if ([scheme caseInsensitiveCompare:HttpProtocolKey] == NSOrderedSame
  /|| [scheme caseInsensitiveCompare:HttpsProtocolKey] == NSOrderedSame/)
  {
  //看看是否已经处理过了，防止无限循环
  if ([NSURLProtocol propertyForKey:kURLProtocolHandledKey inRequest:request]) {
  NSLogInfo(@"hookRequest-canInitWithRequest NO %@",request.URL);
  return NO;
  }
  }
  NSLogInfo(@"hookRequest-canInitWithRequest YES %@",request.URL);
  return YES;
  }
- (NSURLRequest *) canonicalRequestForRequest:(NSURLRequest *)request {
  
  NSMutableURLRequest *mutableReqeust = [request mutableCopy];
  // 执行自定义操作，例如添加统一的请求头等
  return mutableReqeust;
  }
// 判重
- (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b
  {
  return [super requestIsCacheEquivalent:a toRequest:b];
  }
- (void)startLoading
  {
  NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
  // 标示改request已经处理过了，防止无限循环
  [NSURLProtocol setProperty:@YES forKey:kURLProtocolHandledKey inRequest:mutableReqeust];
#if MYSchemeURLHeaderTokenAdd
// 处理请求 body
if (self.request.HTTPBody && [self.request valueForHTTPHeaderField:@"Content-Type"]) {
[mutableReqeust setHTTPBody:self.request.HTTPBody];
[mutableReqeust setValue:[self.request valueForHTTPHeaderField:@"Content-Type"] forHTTPHeaderField:@"Content-Type"];
}
if([mutableReqeust.URL.absoluteString containsString:@"Users/authenticatebyname"]){
NSLogInfo(@"跳过");
}
NSString *body = [NTYJSON parse:mutableReqeust.HTTPBody];
NSLogInfo(@"self.HTTPBody:%@",body);
NSLogInfo(@"self.HTTPBodyStream:%@",mutableReqeust.HTTPBodyStream);
```
  [mutableReqeust appendRemoteAccessHeaders];
```
#endif
```
  // 通知更新URL
  [[NSNotificationCenter defaultCenter] postNotificationName:URLLoadingNotification object:mutableReqeust.URL.absoluteString];
  
  NSURLSessionConfiguration *configure = [NSURLSessionConfiguration defaultSessionConfiguration];
  self.session  = [NSURLSession sessionWithConfiguration:configure delegate:self delegateQueue:self.queue];
  self.task = [self.session dataTaskWithRequest:mutableReqeust];
  [self.task resume];
```
}
- (void)stopLoading
  {
  [self.session invalidateAndCancel];
  self.session = nil;
  [[NSNotificationCenter defaultCenter] postNotificationName:URLLoadingNotification object:@""];
}

#pragma mark - Getter
- (NSOperationQueue *)queue
  {
  if (!_queue) {
  _queue = [[NSOperationQueue alloc] init];
  }
  return _queue;
  }
  @end
@implementation MYSchemeURLProtocol(NSURLSessionDelegate)
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
  {
  if (error != nil) {
  NSLogInfo(@"didComplete url:%@",task.originalRequest.URL.absoluteString);
  // 检查是否为 WKWebView 的网络请求
  [self.client URLProtocol:self didFailWithError:error];
  }else
  {
  [self.client URLProtocolDidFinishLoading:self];
  }
  }
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
  didReceiveResponse:(NSURLResponse *)response
  completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler
  {
  [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
  
  completionHandler(NSURLSessionResponseAllow);
  }
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
  {
  [self.client URLProtocol:self didLoadData:data];
  }
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask willCacheResponse:(NSCachedURLResponse *)proposedResponse completionHandler:(void (^)(NSCachedURLResponse * _Nullable))completionHandler
  {
  completionHandler(proposedResponse);
  }
//TODO: 重定向
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task willPerformHTTPRedirection:(NSHTTPURLResponse *)response newRequest:(NSURLRequest *)newRequest completionHandler:(void (^)(NSURLRequest ))completionHandler
  {
  NSLogInfo(@"hookRequest-willPerformHTTP:%@",newRequest.URL);
  NSMutableURLRequest redirectRequest;
  redirectRequest = [newRequest mutableCopy];
  [[self class] removePropertyForKey:kURLProtocolHandledKey inRequest:redirectRequest];
#if MYSchemeURLHeaderTokenAdd
[redirectRequest appendRemoteAccessHeaders];
#endif
```
  [[self client] URLProtocol:self wasRedirectedToRequest:redirectRequest redirectResponse:response];
  
  [self.task cancel];
  [[self client] URLProtocol:self didFailWithError:[NSError errorWithDomain:NSCocoaErrorDomain code:NSUserCancelledError userInfo:nil]];
```
}

@end

@implementation NSMutableURLRequest (MYHeaderAppend)
/*
还需要增加两个header：
Nas-Neigh-Ip
Nas-Neigh-Port
分别是目标ip和目标端口，请注意port需要用字符串类型
*/
- (BOOL)appendRemoteAccessHeaders {
  //MARK:MY_token 添加进请求头
  // 添加自定义的 HTTP 头
  NSString *tokenValue = [MYUserService shared].currentUser.token;
  NSString *holdToken = [self.allHTTPHeaderFields valueForKey:@"z-token"];
  if([self.URL.absoluteString containsString:@"Users/authenticatebyname"]){
  NSLogInfo(@"跳过");
  }
  if(isEmpty(holdToken)){
  NSString *body = [NTYJSON parse:self.HTTPBody];
  NSLogInfo(@"self.HTTPBody:%@ url:%@",body,self.URL.absoluteString);
  NSLogInfo(@"self.HTTPBodyStream:%@",self.HTTPBodyStream);
  NSURLComponents *remoteURLComs = [NSURLComponents componentsWithString:[MYUserService shared].latestRemoteAccessURL];
  NSString *portStr = STRING(@"%@",[remoteURLComs port]);
  NSString *hostStr = remoteURLComs.host;
  [self setValue:tokenValue forHTTPHeaderField:@"z-token"];
  [self setValue:hostStr forHTTPHeaderField:@"Nas-Neigh-Ip"];
  [self setValue:portStr forHTTPHeaderField:@"Nas-Neigh-Port"];
  NSLogInfo(@"remoteAccessURL&appendheaders::%@\n%@",self.URL,self.allHTTPHeaderFields);
  return YES;
  }
  return NO;
  }
@end
接下来，在需要进行拦截的WebViewController中，注册MYSchemeURLProtocol。核心代码示例如下：

#import "MYWebviewController.h"
#import "MYSchemeURLProtocol.h"

@interface JKJWebviewController ()<WKNavigationDelegate,WKScriptMessageHandler,WKUIDelegate>

@property (nonatomic, strong) WKWebView *webView;
@property (nonatomic, strong) NSURLRequest *request;
@end

@implementation JKJWebviewController
- (void)dealloc {
  [[NSNotificationCenter defaultCenter] removeObserver:self];
  #if JKJSchemeURLHeaderTokenAdd
  if(self.refModule.refModuleRequest == JKJRefModuleRequestRemoteAccessWebLoad){
  [JKJSchemeURLProtocol unregistSchemeURLProtocol];
  }
  #endif
  }
- (void)viewDidLoad {
  [super viewDidLoad];
  //注册代码
  #if JKJSchemeURLHeaderTokenAdd
  if(self.refModule.refModuleRequest == JKJRefModuleRequestRemoteAccessWebLoad){
  [JKJSchemeURLProtocol registSchemeURLProtocol];
  }
  #endif
  
  // Do any additional setup after loading the view.
  self.title = self.webTitle;
  self.edgesForExtendedLayout = UIRectEdgeNone;
  
  WKWebViewConfiguration *configuration = [self configuration];
  WKWebView *webView = [[WKWebView alloc] initWithFrame:self.view.bounds configuration:configuration];
  webView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
  webView.navigationDelegate = self;
  webView.UIDelegate = self;
  [webView.scrollView setShowsVerticalScrollIndicator:NO];
  [self.view addSubview:webView];
  
  if (self.needObserveTitle) {
  [webView addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:NULL];
  }
  
  self.webView = webView;
  
  NSMutableURLRequest *req = [[NSMutableURLRequest alloc] initWithURL:[NSURL fileURLWithPath:urlString]];
  
  [webView loadRequest:req];
  self.request = req;
  }
执行结果：

所有请求都可以进行拦截，
所有get请求结果拦截修改和加载表现正常
post请求中的body体丢失，这个问题暂时无法在所运用的场景中使用到，由于后期很多链接都有post请求转发，并且携带有body体，NSURLProtocol拦截之后body体丢失问题无法得到完整的解决，最后放弃了拦截修改。
暂未找到需求逻辑最佳解决方案，待后续处理补充。