distributeddatamgr_distributeddatamgr_cangjie_wrapper/README.md

distributeddatamgr_distributeddatamgr_cangjie_wrapper(beta feature)

Introduction

The distributeddatamgr_distributeddatamgr_cangjie_wrapper provides persistence of various structured data and synchronization and sharing functions of data between different devices for developers using the Cangjie language for application development on OpenHarmony. The distributeddatamgr_distributeddatamgr_cangjie_wrapper currently under development only supports standard devices.

System Architecture

Figure 1 Distributed Data Management Cangjie Wrapper Architecture Diagram

As shown in the architecture diagram:

Interface Layer:

• DataShare Predicates: Provides developers with data query filtering capabilities, supporting the construction of complex query conditions.

  • Comparison Predicates: Supports equal-to conditions.
  • Logical Predicates: Supports AND conditions.
  • Range Predicates: Supports IN conditions.
  • Sorting Functions: Supports ascending and descending order of result sets.
  • Other Functions: Supports pagination queries. When developers need to retrieve data without focusing on specific database types, data share predicates can be used as general query conditions, such as retrieval of photos and videos in albums.

• Distributed KV Database: Provides developers with cross-device distributed data collaboration capabilities, supporting seamless synchronization and sharing of data between multiple devices.

  • Database Management: Supports database creation, closure, deletion, and obtaining identifier IDs of all created databases.
  • Database Operations: Supports database backup and restore operations.
  • Data Operations: Supports addition, deletion, modification, and query of data records.
  • Transaction Support: Supports transaction enabling, commit, and rollback.
  • Data Subscription: Supports subscription and unsubscription of specified types of data changes.
  • Synchronization Function: Supports end-to-end database synchronization.

• User Preferences: Provides developers with lightweight Key-Value data processing capabilities, specifically for persistent storage of application configuration information and user preferences.

  • Database Management: Supports database acquisition, deletion, and removal from cache.
  • Database Operations: Supports clearing all data, obtaining all data, and data persistence.
  • Data Operations: Supports data writing, searching, and deletion.
  • Data Subscription: Supports subscription and unsubscription of data changes based on Key or Value values, with callback triggering after persistent file changes.

• RDB Store: Provides developers with a complete local database management mechanism based on SQLite components, supporting standard relational data models.

  • Database Management: Supports database creation and deletion.
  • Database Operations: Supports database backup and restore operations.
  • Data Operations: Provides addition, deletion, modification, and query of data records.
  • SQL Execution: Supports direct execution of user-defined SQL statements, including table structure definition and data manipulation for complex database operations. Currently, only the creation and deletion of tables via SQL statements are supported.

• Value Bucket: Provides developers with standardized data field type enumeration classes, including Integer, Double, StringValue, and Boolean.

Framework Layer:

• DataShare Predicates Wrapper: Implements data share predicates wrapper based on the underlying data sharing component, providing data share predicates for different query methods.
• Distributed KV Store Wrapper: Implements distributed key-value database wrapper based on the underlying KV database component, providing key-value pair data management capabilities.
• User Preferences Wrapper: Implements preferences wrapper based on the underlying preferences component, providing lightweight Key-Value operations and supporting local applications to store small amounts of data.
• RDB Store Wrapper: Implements relational database wrapper based on the underlying relational database component, providing a database that manages data based on the relational model.
• Value Bucket Wrapper: Implements standardized data field type enumerations.

Dependencies Introduction in Architecture:

• data_share: The DataShare Predicates Wrapper depends on the data_share, which is used to implement filtering conditions for querying data in databases.
• kv_store: The Distributed KV Store Wrapper relies on the kv_store implement distributed collaboration capabilities of databases between different devices.
• preferences: The User Preferences Wrapper depends on the preferences, which is used to implement lightweight local Key-Value type data processing capabilities.
• relational_store: The RDB Store Wrapper relies on the relational_store to implement local relational database management mechanisms.
• ability_cangjie_wrapper: The Distributed KV Store Wrapper, User Preferences Wrapper, and RDB Store Wrapper depend on the application context capability of ability_cangjie_wrapper, which is used for accessing database resources of the current application, among other purposes.
• hiviewdfx_cangjie_wrapper: Framework Layer depends on HiLog capabilities for printing logs at key points.
• cangjie_ark_interop: Framework Layer depends on APILevel class definitions and BusinessException class definitions for API annotation and throwing exceptions to users in error branches.

Directory Structure

The directory structure is as follows:

foundation/communication/netmanager_cangjie_wrapper
├── figures          # architecture pictures
├── kit              # Cangjie kit code
│   └── ArkData      # ArkData module implementation
└── ohos             # Cangjie distributed data management interface implementation
│   └── data
│       ├── data_share_predicates     # Data share predicates module
│       ├── distributed_kv_store      # Distributed key-value database module
│       ├── preferences               # User preferences module
│       ├── relational_store          # Relational database module
│       └── values_bucket             # Value bucket module
└── test             # Cangjie distributed data management test cases
    ├── data_share_predicates # Data share predicates test cases
    ├── distributed_kv_store  # Distributed key-value database test cases
    ├── preferences           # User preferences test cases
    └── relational_store      # Relational database test cases

Usage

The distributeddatamgr_distributeddatamgr_cangjie_wrapper provides the following functions:

• DataShare Predicates.
• Distributed KV Store.
• User Preferences.
• RDB Store.
• Value Bucket.

For distributed data management related APIs, please refer to:

1. ohos.data.data_share_predicates
2. ohos.data.distributed_kv_store
3. ohos.data.preferences
4. ohos.data.relational_store
5. ohos.data.values_bucket

For related guidance, please refer to Distributed Data Management Development Guide

Constraints

Compared to ArkTS API，the following functions are not supported:

• Common Data Types.
• DataAbility Predicates.
• DataShare.
• Distributed Data Object.
• Shared User Preferences.
• Shared RDB Store.
• Unified Data Channel.
• Uniform Data Structs.
• Uniform Data Definition and Description.
• ArkData Intelligence Platform.
• Device-Cloud Service.

RDB Store does not currently support the following functions:

• Transactions.

Code Contribution

Developers are welcome to contribute code, documentation, etc. For specific contribution processes and methods, please refer to Code Contribution.

Repositories Involved

ability_ability_cangjie_wrapper

arkcompiler_cangjie_ark_interop

distributeddatamgr_data_share

distributeddatamgr_kv_store

distributeddatamgr_preferences

distributeddatamgr_relational_store

hiviewdfx_hiviewdfx_cangjie_wrapper