// 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];