After uploading a file to Firebase 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 Firebase Storage reference using
the getMetadata()
method.
// Create a storage reference from our app StorageReference storageRef = storage.getReferenceFromUrl("gs://<your-bucket-name>"); // 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.getReferenceFromUrl("gs://<your-bucket-name>"); // 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 as a Map<String, String>
.
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 |
getGenerator |
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 |
Map<String, String> |
YES |
Uploading, downloading, and updating files is important, but so is being able to remove them. Let's learn how to delete files from Firebase Storage.