退出时，做了如下操作：

• (void)deleteCredient
  {

    
     //1、
  NSDictionary *credentialsDict = [[NSURLCredentialStorage sharedCredentialStorage] allCredentials];
  if ([credentialsDict count] > 0) {
      // the credentialsDict has NSURLProtectionSpace objs as keys and dicts of userName => NSURLCredential
      NSEnumerator *protectionSpaceEnumerator = [credentialsDict keyEnumerator];
      id urlProtectionSpace;
      // iterate over all NSURLProtectionSpaces
      while (urlProtectionSpace = [protectionSpaceEnumerator nextObject]) {
          NSEnumerator *userNameEnumerator = [[credentialsDict objectForKey:urlProtectionSpace] keyEnumerator];
          id userName;
          // iterate over all usernames for this protectionspace, which are the keys for the actual NSURLCredentials
          while (userName = [userNameEnumerator nextObject]) {
              NSURLCredential *cred = [[credentialsDict objectForKey:urlProtectionSpace] objectForKey:userName];
              [[NSURLCredentialStorage sharedCredentialStorage] removeCredential:cred forProtectionSpace:urlProtectionSpace];
          }
      }
  }
  
  //2、
  NSURLCache *sharedCache = [NSURLCache sharedURLCache];
  [sharedCache removeAllCachedResponses];
  
  //3、
  NSHTTPCookieStorage *cookieStorage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
  NSArray *cookies = [cookieStorage cookies];
  for (NSHTTPCookie *cookie in cookies) {
      [cookieStorage deleteCookie:cookie];
      NSLog(@"deleted cookie");
  }
  [[NSUserDefaults standardUserDefaults]synchronize];
    
   

  }
  再次登陆时，先获取到当前的登陆账号和密码，account,passwd并缓存到本地，
  所有的请求接口都被封装在如下方法中，采用的是NTLM认证:

• (void)getWithURL:(NSString )url params:(NSDictionary )params success:(void (^)(id))success failure:(void (^)(NSError *))failure
  {

    
     AFHTTPRequestOperationManager *mgr = [AFHTTPRequestOperationManager manager];
  NSString *account = [ZYFUserDefaults objectForKey:ZYFAccountKey];
  NSString *passwd = [ZYFUserDefaults objectForKey:ZYFPwdKey];
  NSURLCredential *credential =  [NSURLCredential credentialWithUser:[@"XXXXXX\\" stringByAppendingString:account] password:passwd
                                                         persistence:NSURLCredentialPersistenceForSession];
  
  mgr.credential = credential;                                                     
  [mgr GET:url parameters:params
   success:^(AFHTTPRequestOperation *operation, id responseObject) {
       if (success) {
           success(responseObject);
       }
   } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
       if (failure) {
           failure(error);
       }
   }];
    
   

  }