The **DataShare** module allows an application to share its data with other applications. Currently, data can be shared only between applications on the same device.
The application data on a device, such as the Contacts, short message service (SMS), and Gallery data, always needs to be shared with other applications. However, certain data, such as the accounts and passwords, cannot be shared. Certain data, such as SMS messages, can be accessed but not modified by other applications. The **DataShare** module provides a secure and easy-to-use mechanism for sharing data of an application with other applications on the same device.
Data needs to be shared in a wealth of scenarios. For example, the Contacts, short message service (SMS), and Gallery data always needs to be shared with other applications. However, certain data, such as accounts and passwords, cannot be shared. Some data, such as SMS messages, can be queried but not modified by other applications. **DataShare** provides a secure and convenient sharing mechanism for application data.
## Basic Concepts
The data provider can directly use **DataShare** to share data with other applications without complex encapsulation. The data consumer only needs to use a set of APIs because the DataShare access mode does not vary with the data provision mode. This greatly reduces the learning time and development difficulty.
Before developing cross-application data sharing on a device, understand the following concepts:
Data can be shared across applications in either of the following ways:
- Data provider: an application that provides data and implements related services. It is also called the data producer or server.
- Using **DataShareExtensionAbility**
An extension ability is implemented in the HAP to invoke a callback. When the data consumer calls an API, the extension ability of the data provider will be automatically started to invoke the registered callback.
- Data consumer: an application that accesses the data or services provided by the data provider. It is also called the client.
You can use **DataShareExtensionAbility** when the cross-application data access involves service operations other than mere addition, deletion, modification, and query of data in databases.
-**ValuesBucket**: a set of data to be inserted. It can be one or more data records in KV pairs. In each KV pair, the key must be of the string type, and the value can be a number, a string, a Boolean value, or an unsigned integer array.
- Using Silent Access
Database access rules are configured in the HAP. When the data consumer calls an API, the system ability automatically obtains the access rules in the HAP and returns data without starting the data provider.
-**ResultSet**: a set of query results. It provides flexible modes for obtaining various data.
You can use the silent access feature when the cross-application data access involves only the operations for adding, deleting, modifying, and querying data in databases.
-**Predicates**: an object that specifies the conditions for updating, deleting, or querying data in a database.
## Basic Concepts
## Implementation
Before developing cross-application data sharing on a device, understand the following concepts:
The data provider can directly use **DataShare** to share data with other applications without complex encapsulation. The data consumer only needs to use a set of APIs to access the data, because the **DataShare** access mode does not vary with the data provisioning mode. This greatly reduces the learning time and development difficulty.
- Data provider: an application that provides data and implements related services. It is also called the producer or server.
The cross-application data sharing can be implemented in either of the following ways:
-Data consumer: an application that accesses the data or services provided by the data provider. It is also called the client.
-**DataShareExtensionAbility**
-**ValuesBucket**: a set of data to be inserted. It can be one or more data records in KV pairs. In each KV pair, the key must be of the string type, and the value can be a number, a string, a Boolean value, or an unsigned integer array.
You can implement an ExtensionAbility with a callback in the HAP. When the data consumer calls an API, the ExtensionAbility of the data provider will be automatically started to invoke the registered callback.
-**ResultSet**: a set of query results. It provides flexible modes for users to obtain various data.
This method is recommended when the cross-application data access involves service operations other than mere addition, deletion, modification, and query of data in databases.
-**Predicates**: an object that specifies the conditions for updating, deleting, or querying data in a database.
- Silent access
You can configure database access rules in the HAP. When the data consumer calls an API, the system ability automatically obtains the access rules in the HAP and returns data without starting the data provider.
This method is recommended when the cross-application data access involves only the operations for adding, deleting, modifying, and querying data in databases.
## Constraints
-**DataShare** is subject to the limitations on the database used by the data provider. For example, the supported data models, length of the keys and values, and maximum number of databases that can be accessed at a time by each application vary with the database in use.
-**DataShare** is subject to the limitations on the database used by the data provider. The supported data models, length of the keys and values, and maximum number of databases that can be accessed at a time by each application vary with the database in use.
- The payloads of **ValuesBucket**, **Predicates**, and **ResultSet** are restricted by IPC.
- The payloads of **ValuesBucket**, **Predicates**, and **ResultSet** are restricted by inter-process communication (IPC).
- Currently, **dataShare** supports development based on the stage model only.
