Use File Metadata on Android

After uploading a file to Cloud Storage reference, you can also get and update the file metadata, for example to view or update the content type. Files can also store custom key/value pairs with additional file metadata.

Get File Metadata

File metadata contains common properties such as name, size, and contentType (often referred to as MIME type) in addition to some less common ones like contentDisposition and timeCreated. This metadata can be retrieved from a Cloud Storage reference using the getMetadata() method.

// Create a storage reference from our app
StorageReference storageRef = storage.getReference();

// Get reference to the file
StorageReference forestRef = storageRef.child("images/forest.jpg");

forestRef.getMetadata().addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
    @Override
    public void onSuccess(StorageMetadata storageMetadata) {
        // Metadata now contains the metadata for 'images/forest.jpg'
    }
}).addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception exception) {
        // Uh-oh, an error occurred!
    }
});

Update File Metadata

You can update file metadata at any time after the file upload completes by using the updateMetadata() method. Refer to the full list for more information on what properties can be updated. Only the properties specified in the metadata are updated, all others are left unmodified.

// Create a storage reference from our app
StorageReference storageRef = storage.getReference();

// Get reference to the file
StorageReference forestRef = storageRef.child("images/forest.jpg");

// Create file metadata including the content type
StorageMetadata metadata = new StorageMetadata.Builder()
        .setContentType("image/jpg")
        .setCustomMetadata("myCustomProperty", "myValue")
        .build();

// Update metadata properties
forestRef.updateMetadata(metadata)
        .addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
            @Override
            public void onSuccess(StorageMetadata storageMetadata) {
                // Updated metadata is in storageMetadata
            }
        })
        .addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception exception) {
                // Uh-oh, an error occurred!
            }
        });

You can delete writable metadata properties by passing null:

// Create file metadata with property to delete
StorageMetadata metadata = new StorageMetadata.Builder()
.setContentType(null)
.build();

// Delete the metadata property
forestRef.updateMetadata(metadata)
.addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
    @Override
    public void onSuccess(StorageMetadata storageMetadata) {
        // metadata.contentType should be null
    }
})
.addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception exception) {
        // Uh-oh, an error occurred!
    }
});

Handle Errors

There are a number of reasons why errors may occur on getting or updating metadata, including the file not existing, or the user not having permission to access the desired file. More information on errors can be found in the Handle Errors section of the docs.

Custom Metadata

You can specify custom metadata using the setCustomMetadata() method in the StorageMetadata.Builder class.

metadata = new StorageMetadata.Builder()
        .setCustomMetadata("location", "Yosemite, CA, USA")
        .setCustomMetadata("activity", "Hiking")
        .build();

You can store app-specific data for each file in custom metadata, but we highly recommend using a database (such as the Firebase Realtime Database) to store and synchronize this type of data.

File Metadata Properties

A full list of metadata properties on a file is available below:

Property Getter Type Setter Exists
getBucket String NO
getGeneration String NO
getMetadataGeneration String NO
getPath String NO
getName String NO
getSizeBytes long NO
getCreationTimeMillis long NO
getUpdatedTimeMillis long NO
getMd5Hash String NO
getCacheControl String YES
getContentDisposition String YES
getContentEncoding String YES
getContentLanguage String YES
getContentType String YES
getDownloadUrl Uri NO
getDownloadUrls List<Uri> NO
getCustomMetadata String YES
getCustomMetadataKeys Set<String> NO

Uploading, downloading, and updating files is important, but so is being able to remove them. Let's learn how to delete files from Cloud Storage.

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