Accessing Backup and Restore

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

BackupExtensionAbility is a class derived from ExtensionAbility in the stage model. The application that has accessed the backup and restore framework can customize the backup and restore behavior, including whether to enable backup and restore and specifying the data to be backed up, in a profile.

Available APIs

For details about how to use the APIs, see BackupExtensionAbility and Backup and Restore Extension Capability.

Constraints

• The path of the file or directory to be backed up or restored 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 all the ancestor directories of the file (x in DAC). Otherwise, the backup fails.
• The path of the file or directory to be backed up or restored does not support relative paths (../) and soft links.

How to Develop

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

In module.json5, add the extensionAbilities field, set type to backup, and add a record with name set to ohos.extension. backup under “metadata”.

Example:

   {
       "extensionAbilities": [
           {
               "description": "$string:ServiceExtAbility",
               "icon": "$media:icon",
               "name": "BackupExtensionAbility",
               "type": "backup",
               "exported": false,
               "metadata": [
                   {
                       "name": "ohos.extension.backup",
                       "resource": "$profile:backup_config"
                   }
               ],
               // In the BackupExtension.ets file, define BackupExtensionAbility in extensionAbilities and override onBackup or onBackupEx
               // and onRestore or onRestoreEx methods. The onBackupEx and onRestoreEx methods are recommended.
               // Empty implementation can be used if there is no special requirement. In this case, the backup and restore service backs up or restores data based on the unified backup and restore rules.
               "srcEntry": "./ets/BackupExtension/BackupExtension.ets"
           }      
       ]
   }

1. Add a metadata profile.

The metadata profile defines the files to be transferred during the backup and restore process. The profile is located in the resources/base/profile directory of the project, and the file name must be the same as the value of metadata.resource, for example, backup_config.json in the module.json5 file.

Metadata profile example:

   {
       "allowToBackupRestore": true,
       "includes": [
           "/data/storage/el2/base/files/users/"
       ],
       "excludes": [
           "/data/storage/el2/base/files/users/hidden/"
       ],
       "fullBackupOnly": false,
       "restoreDeps": ""
   }

1. Customize BackupExtensionAbility in the BackupExtension.ets file and override onBackup/onBackupEx or onRestore/onRestoreEx to back up preprocessed application data or process the data to be restored.

Empty implementation can be used if there is no special requirement. In this case, the backup and restore service backs up or restores data based on the unified backup and restore rules.

The following example shows an empty implementation of the BackupExtension.ets file.

```ts
//onBackup && onRestore
import { BackupExtensionAbility, BundleVersion } from '@kit.CoreFileKit';
import {hilog} from '@kit.PerformanceAnalysisKit';

const TAG = `FileBackupExtensionAbility`;
export default class BackupExtension extends  BackupExtensionAbility {
  //onBackup
  async onBackup ()   {
    hilog.info(0x0000, TAG, `onBackup ok`);
  }
  //onRestore
  async onRestore (bundleVersion : BundleVersion) {
    hilog.info(0x0000, TAG, `onRestore end`);
  }
}
```

```ts
//onBackupEx && onRestoreEx
import { BackupExtensionAbility, BundleVersion } from '@kit.CoreFileKit';

interface ErrorInfo {
  type: string,
  errorCode: number,
  errorInfo: string
}

class BackupExt extends BackupExtensionAbility {
  //onBackupEx
  async onBackupEx(backupInfo: string): Promise<string> {
    console.info(`onBackupEx ok`);
    let errorInfo: ErrorInfo = {
      type: "ErrorInfo",
      errorCode: 0,
      errorInfo: "app diy error info"       
    }
    return JSON.stringify(errorInfo);
  }

  // onRestoreEx
  async onRestoreEx(bundleVersion : BundleVersion, restoreInfo: string): Promise<string> {
    console.info(`onRestoreEx begin`);
    let errorInfo: ErrorInfo = {
      type: "ErrorInfo",
      errorCode: 0,
      errorInfo: "app diy error info"
    }
    return JSON.stringify(errorInfo);
  }
}
```

Description of the Metadata Profile

NOTE

When setting fullBackupOnly, observe the following:

• If fullBackupOnly is set to false, the restored data will be decompressed in the root directory /, and the file with the same name in the directory will be overwritten.
• If fullBackupOnly is set to true, the restored data will be decompressed in a temporary directory. You need to implement the data restoration logic in OnRestore or OnRestoreEx.

You can determine the data restore mode to use based on service requirements.

Example: Assume that the application backup path is data/storage/el2/base/files/A/. If fullBackupOnly is false, the restored data will be decompressed to the /data/storage/el2/base/files/A/ directory. If fullBackupOnly is true, data will be decompressed to the temporary directory backupDir/restore/data/storage/el2/base/files/A/.

The following lists the paths supported by includes:

{
    "includes": [
    "data/storage/el1/database/",
    "data/storage/el1/base/files/",
    "data/storage/el1/base/preferences/",
    "data/storage/el1/base/haps/*/files/",
    "data/storage/el1/base/haps/*/preferences/",
    "data/storage/el2/database/",
    "data/storage/el2/base/files/",
    "data/storage/el2/base/preferences/",
    "data/storage/el2/base/haps/*/files/",
    "data/storage/el2/base/haps/*/preferences/",
    "data/storage/el2/distributedfiles/",
    "data/storage/el5/database/",
    "data/storage/el5/base/files/",
    "data/storage/el5/base/preferences/",
    "data/storage/el5/base/haps/*/files/",
    "data/storage/el5/base/haps/*/preferences/"
    ]
}

-

你可能感兴趣的鸿蒙文章

harmony 鸿蒙Core File Kit

harmony 鸿蒙Accessing Application Files (ArkTS)

harmony 鸿蒙Application Data Backup and Restore Overview

harmony 鸿蒙Backup and Restore Triggered by System Applications

harmony 鸿蒙Application File Overview

harmony 鸿蒙Obtaining Application and File System Space Statistics

harmony 鸿蒙Application Sandbox

harmony 鸿蒙Introduction to Core File Kit

harmony 鸿蒙Developing a File Manager Application (for System Applications Only)

harmony 鸿蒙Distributed File System Overview