最近在公司做了一个混合开发的项目，有个需求是要加载本地的加密页面。所以就写了个NSURLProtocol的子类去拦截UIWebView的所有页面请求，再将本地的加密的页面解密后返回。

注册自定义的NSURLProtocol

[NSURLProtocol registerClass:[MyURLProtocaol class]]

先定义一个全局变量

static NSString * const URLProtocolHandledKey = @"URLProtocolHandledKey";

然后就可以实现几个方法

• +canInitWithRequest:

  + (BOOL)canInitWithRequest:(NSURLRequest *)request{
    
    NSString *url = request.URL.absoluteString;
    
    // 如果url以https或http开头，则不拦截处理
    if ([url hasPrefix:@"https"] || [url hasPrefix:@"http"]) {
        return NO;
    }
    
    //看看是否已经处理过了，防止无限循环
    if ([NSURLProtocol propertyForKey:URLProtocolHandledKey inRequest:request]) {
        return NO;
    }
    
    return YES;
    }
  

• -startLoading

  - (void)startLoading{
  
  NSMutableURLRequest *mutableReqeust = [[self request] mutableCopy];
  //打标签，防止无限循环
  [NSURLProtocol setProperty:@YES forKey:URLProtocolHandledKey inRequest:mutableReqeust];
  
  NSString *requestStr = [mutableReqeust.URL absoluteString];
  
  //多加一层判断，只处理加载本地文件的请求
  if (![requestStr hasPrefix:@"file:"]) {
      
      self.connection = [NSURLConnection connectionWithRequest:mutableReqeust delegate:self];
      return;
  }
  
  //对拦截的请求进行处理
  NSData *de_data = [[NSData dataWithContentsOfURL:mutableReqeust.URL] AES128DecryptWithKey:@"Ctl62fuMCkfSPl/+" iv:@"0000000000123456"];
  
  NSURLResponse *response = [[NSURLResponse alloc] initWithURL:[self.request URL] MIMEType:@"application/octet-stream" expectedContentLength:-1 textEncodingName:nil];
  [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
  [self.client URLProtocol:self didLoadData:de_data];
  [self.client URLProtocolDidFinishLoading:self];
  
  self.connection = [NSURLConnection connectionWithRequest:mutableReqeust delegate:self];
  

}

###最主要就是以上两个方法，其它的方法如下

• (NSURLRequest *) canonicalRequestForRequest:(NSURLRequest *)request {

  return request;
  }

• (BOOL)requestIsCacheEquivalent:(NSURLRequest *)a toRequest:(NSURLRequest *)b{

  return [super requestIsCacheEquivalent:a toRequest:b];
  }

• (void)stopLoading{

  [self.connection cancel];
  }

pragma mark - NSURLConnectionDelegate

• (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

  [self.client URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
  }

• (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {

  [self.client URLProtocol:self didLoadData:data];
  }

• (void) connectionDidFinishLoading:(NSURLConnection *)connection {

  [self.client URLProtocolDidFinishLoading:self];
  }

• (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

  [self.client URLProtocol:self didFailWithError:error];
  }

>刚刚开始的时候没有注意，没有把http和https的请求剔除，所以出现了如果涉及到加载互联网网址的时候，有些网站会加载不正常，所以要注意。