**错误处理**
##########################

1.通用的错误处理：

S3有一个通用的错误处理类：awserr.Error，通过了以下方法获取出错信息：


================  =============================================================
 方法                     说明
================  =============================================================
  Code              returns the classification code by which related errors are grouped.
  Message           returns a description of the error.
  OrigError         returns the original error of type error that is wrapped by the awserr.Error interface, such as a standard library error or a service error.
================  =============================================================


awserr.Error的定义如下：

.. code::

    type Error interface {
        // Satisfy the generic error interface.
        error

        // Returns the short phrase depicting the classification of the error.
        Code() string

        // Returns the error details message.
        Message() string

        // Returns the original error if one was set.  Nil is returned if not set.
        OrigErr() error
    }

2.处理特殊的出错

.. code::

    svc := s3.New(sess)
    resp, err := svc.GetObject(&s3.GetObjectInput{
        Bucket: aws.String(os.Args[1]),
        Key:    aws.String(os.Args[2]),
    })

    if err != nil {
        // http://docs.aws.amazon.com/AmazonS3/latest/API/ErrorResponses.html
        if aerr, ok := err.(awserr.Error); ok {
            switch aerr.Code() {
            case s3.ErrCodeNoSuchBucket:
                exitErrorf("bucket %s does not exist", os.Args[1])
            case s3.ErrCodeNoSuchKey:
                exitErrorf("object with key %s does not exist in bucket %s", os.Args[2], os.Args[1])
            }
        }    
    }


=================================  ===================
  Code                               description
=================================  ===================
 ErrCodeNoSuchBucket                  桶不存在
 ErrCodeNoSuchKey                     对象不存在
 ErrCodeBucketAlreadyExists           桶已经被创建了，不属于您
 ErrCodeBucketAlreadyOwnedByYou       桶已经被创建了，且是您创建的
 ErrCodeNoSuchUpload                  分块上传不存在
=================================  ===================


3.特殊的错误接口：MultiUploadFailure

接口定义如下：

.. code:: 

    type MultiUploadFailure interface {
        awserr.Error

        // Returns the upload id for the S3 multipart upload that failed.
        UploadID() string
    }