Object metadata includes HTTP headers and user metadata. You can configure the metadata of an object when you upload the object to Object Storage Service (OSS). The metadata of an object is uploaded and downloaded together with the object.

Usage notes

  • When you use packaging tools such as Webpack and Browserify, install OSS SDK for Browser.js by running the npm install ali-oss command.
  • OSS SDK for Browser.js is usually used in browsers. To prevent your AccessKey pair from being exposed, we recommend that you use a temporary access credential generated by Security Token Service (STS) to access OSS.

    For more information about how to set up STS, see Use a temporary access credential provided by STS to access OSS in OSS Developer Guide. You can call the AssumeRole operation or use STS SDKs for various programming languages to obtain a temporary access credential. For more information, see STS SDK overview. A temporary access credential contains a security token and a temporary AccessKey pair that consists of an AccessKey ID and an AccessKey secret.

Sample code

The following code provides an example on how to specify object metadata during uploads and how to update and view object metadata after uploads:

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8" />
  <title>Document</title>
</head>

<body>
  <button id='upload'>Upload An Object</button>
  <button id='update'>Modify Object Metadata</button>
  <button id='check'>View Object Metadata</button>
    <!-- import an SDK file -->
  <script type="text/javascript" src="https://gosspublic.alicdn.com/aliyun-oss-sdk-6.16.0.min.js"></script>
  <script type="text/javascript">
    const client = new OSS({
       // Set yourRegion to the endpoint of the region in which the bucket is located. For example, if your bucket is located in the China (Hangzhou) region, set yourRegion to oss-cn-hangzhou. 
       region: 'yourRegion',
       // Specify the temporary AccessKey pair obtained from STS. 
       accessKeyId: 'yourAccessKeyId',
       accessKeySecret: 'yourAccessKeySecret',
       // Specify the security token obtained from STS. 
       stsToken: 'yourSecurityToken',
       // Specify the name of the bucket. Example: examplebucket. 
       bucket: "examplebucket",
     });

    const upload = document.getElementById('upload')
    const update = document.getElementById('update')
    const check = document.getElementById('check')

    // Specify the local file to upload. 
    const file = new Blob(['examplecontent'])
    // Specify the name of the object that is uploaded to the bucket. 
    const fileName = 'exampleobject.txt'

    // Upload the object. 
    upload.addEventListener('click', () => {
     client.put(fileName, file, {
        // Configure the user metadata of the object. You can configure multiple metadata attributes for an object. However, the total size of the object metadata cannot exceed 8 KB. 
        meta: {
          year: 2020,
          people: 'eliot'
        }
      }).then(r => console.log(r))
    })

    // Modify the object metadata. 
    update.addEventListener('click', () => {
      client.putMeta(fileName, {
        year: 2021,
        people: 'evan'
      }
      ).then(r => {
        console.log(r)
      })
    })
    // View the object metadata. 
    check.addEventListener('click', () => {
      client.head(fileName).then(m => console.log(m))
    })

  </script>
</body>

</html>

References

  • For more information about the complete sample code for object metadata management, visit GitHub.
  • For more information about the operation that is called to configure or modify object metadata during uploads, see PutObject.
  • For more information about the API operation that is called to view object metadata, see HeadObject.