// 1.初始化单例类

     AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];

    manager.securityPolicy.SSLPinningMode = AFSSLPinningModeCertificate;   

// 2.设置证书模式

    NSString * cerPath = [[NSBundle mainBundle] pathForResource:@"xxx" ofType:@"cer"];    

NSData * cerData = [NSData dataWithContentsOfFile:cerPath];

    manager.securityPolicy = [AFSecurityPolicy policyWithPinningMode:AFSSLPinningModeCertificate withPinnedCertificates:[[NSSet alloc] initWithObjects:cerData, nil]];   

    manager.securityPolicy.allowInvalidCertificates = NO;   

    [manager.securityPolicy setValidatesDomainName:YES];