Use the SDK

Business data storage

The business data storage module uses Preference for in-memory storage. It supports the following data types: number, string, boolean, Array<number>, Array<boolean>, Array<Uint8Array>, and Uint8Array.

The application's memory usage increases with the amount of data stored in Preferences. Preferences is not suitable for storing large amounts of data and does not support encryption through configuration.

Constraints

• Preference is not process-safe, which creates a risk of file corruption and data loss. Therefore, using Preference in multi-process scenarios is not supported.

• The key must be a non-empty string with a maximum length of 1024 bytes.

• If the value is a string, it must use the UTF-8 encoding format. The string can be empty, but its length cannot exceed 16 MB.

• To store data that contains non-UTF-8 strings, use the Uint8Array type. This prevents formatting errors in the persistent file.

• Memory usage increases with the storage data size. Keep the data volume small, preferably under 50 MB. With large data volumes, creating Preference objects and persisting data using the sync API is a time-consuming operation. Do not perform this operation in the main thread, because it may cause the application to freeze.

Create a business data table

let mpData: MPData = MPData.createData('xxx')

CRUD operations

let mpData: MPData = MPData.createData('xxx')
mpData.put(key,value)
mpData.putObject(key,object)

mpData.delete(key)

mpData.get(key):preferences.ValueType
mpData.getAll(): [string,string[]]

Synchronization

If you do not call the sync API, the data is stored only in memory. After you call the sync API, the data is persisted to a serialized file.

mpData.synchronize()

Clear data

mpData.clear()

Global User Storage

CRUD operations

import { MPData } from "@mpaas/datacenter"

// Store data
// Basic data types
MPData.put(key, value).then().catch() // Default global storage
MPData.put(key, value,{userId:""}).then().catch() // User-associated data storage
MPData.put(key, value,{encrypt: true}).then().catch() // Use encrypted storage

// object
MPData.putObject(key, value).then().catch()
MPData.putObject(key, value,{userId:""}).then().catch() // User-associated data storage
MPData.putObject(key, value,{encrypt: true}).then().catch() // Use encrypted storage

// Batch operations
MPData.putBatch(values).then().catch()
MPData.putBatch(values,{userId:""}).then().catch() // User-associated data storage
MPData.putBatch(values,{encrypt: true}).then().catch() // Use encrypted storage

// Retrieve a value
MPData.get(key).then().catch() 
MPData.get(key,{userId:""}).then().catch() // User-associated data
MPData.get(key,{encrypt: true}).then().catch() // Use encryption

// Delete
await MPData.delete(key)
await MPData.delete(key,{userId : "" })
await MPData.delete(key,{encrypt:true})

Reset data

// Reset
await MPData.resetGlobalStore() // Global data
await MPData.resetUserStore(userId) // User data

Query all data for specified parameters

// Get all data
await MPData.getAllData() // Global data
await MPData.getAllData(userId) // User data

Close the connection

Close the database connection after you finish using the data. The underlying layer of HarmonyOS limits the maximum number of concurrent database connection pools to 8. An exception is thrown if this limit is exceeded.

await MPData.close() 

Get a data array for a specified prefix

MPData.getEntries(keyPrefix).then((data)=>{
	// data is a JSON string 
}).catch()

MPData.getEntries(keyPrefix,{userId:""}).then().catch() // User-associated data
MPData.getEntries(keyPrefix,{encrypt: true}).then().catch() // Use encryption

 let fileUtil = new MPFile()
// Store a file. encrypt: specifies whether to encrypt the file.
public async saveFile(fileName: string , content: string, encrypt: boolean = false)
// Get the file content.
public async getFileContent(fileName: string, encrypt: boolean = false) 
// Delete a file.
public async removeFile(fileName: string) 

Dataset operations

1. Call getResult to retrieve the dataset.

   // Get the dataset for a specified prefix
   MPData.getResult(keyPrefix).then().catch()
   MPData.getResult(keyPrefix,{userId:""}).then().catch()
   MPData.getResult(keyPrefix,{encrypt:true}).then().catch()

2. Call the following APIs. The parameters must be consistent.

   MPData.getCount() 
   
   // Current cursor position
   MPData.getPosition()
   
   // Move the cursor
   MPData.moveToFirst()
   
   MPData.moveToNext()
   
   MPData.moveToPrevious()
   
   MPData.move(offset)
   
   MPData.moveToPosition(position)
   
   // Check the cursor position
   MPData.isFirst()
   
   MPData.isLast()
   
   MPData.isBeforeFirst()
   
   MPData.isAfterLast()
   
   // Get the data at the current cursor position
   MPData.getEntry()