harmony 鸿蒙Backup and Restoration Accessed by Applications

2023-06-24
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Backup and Restoration Accessed by Applications

You can use BackupExtensionAbility to enable an application to access the backup and restoration framework.

BackupExtensionAbility is a class derived from the ExtensionAbility based on the stage model. You can modify the configuration file to customize the backup and restoration framework behavior, including whether to allow backup and restoration and specifying the files to be backed up.

Constraints

The paths of all files and directories to be backed up cannot exceed 4095 bytes. Otherwise, undefined behavior may occur.
If a directory needs to be backed up, the application process must have the permission to read the directory and all its subdirectories (r in DAC). Otherwise, the backup fails.
If a file needs to be backed up, the application process must have the permission to retrieve the grandparent directory of the file (x in DAC). Otherwise, the backup fails.

How to Develop

Add extensionAbilities to the application’s module.json5 file.

Add the extensionAbilities field, set type to backup, and add a record with name of ohos.extension.backup to metadata.

BackupExtensionAbility configuration example:

   {
       "extensionAbilities": [
           {
               "description": "$string:ServiceExtAbility",
               "icon": "$media:icon",
               "name": "BackupExtensionAbility",
               "type": "backup",
               "visible": true,
               "metadata": [
                   {
                       "name": "ohos.extension.backup",
                       "resource": "$profile:backup_config"
                   }
               ],
               "srcEntrance": "",
           }      
       ]
   }

Add a metadata resource profile.

The metadata resource profile defines the files to be transferred during the backup and restoration process. The file is located in the resource/profile directory of the project, and the file name must be the same as metadata.resource in the module.json5 file.

Metadata resource profile example:

   {
       "allowToBackupRestore": true,
       "includes": [
           "/data/storage/el2/base/files/users/*/*.json"
       ],
       "excludes": [
           "/data/storage/el2/base/files/users/*/hidden.json"
       ],
   }

Description of the Metadata Resource Configuration File

Name	Type	Mandatory	Description
allowToBackupRestore	Boolean	Yes	Whether to allow backup and restoration. The default value is false.
includes	String array	No	Files and directories to be backed up in the application sandbox. Each item in the array is a pattern string, which can contain shell-style wildcards such as ``, `?`, `[`. The pattern string that does not start with a slash (/) indicates a relative path. If includes* is configured, the backup and restoration framework uses the pattern strings configured. Otherwise, the backup and restoration framework uses the includes default value (see the following code segment).
excludes	String array	No	Items in includes that do not need to be backed up. The value is in the same format as includes. If excludes is configured, the backup and restoration framework uses the pattern strings configured. Otherwise, the backup and restoration framework uses an empty array as the default value.

includes default value:

{
    "includes": [
    "data/storage/el2/database/",
    "data/storage/el2/base/files/",
    "data/storage/el2/base/preferences/",
    "data/storage/el2/base/haps/*/database/",
    "data/storage/el2/base/haps/*/files/",
    "data/storage/el2/base/haps/*/preferences/",
    ]
}