1# Sharing Data via Unified Data Channels 2 3 4## When to Use 5 6In many-to-many data sharing across applications, a data channel needs to be provided to access data of different applications and share the data with other applications. 7 8The Unified Data Management Framework (UDMF) provides unified data channels and standard data access interfaces for different service scenarios of many-to-many cross-application data sharing. 9 10## Definition and Implementation of Unified Data Channels 11 12The unified data channel provides cross-application data access for various service scenarios. It can temporarily store the unified data objects to be shared by an application, and manage the data modification and deletion permissions and lifecycle of the data according to certain policies. 13 14The unified data channel is implemented by the system ability provided by the UDMF. When an application (data provider) needs to share data, it calls the **insertData()** method provided by the UDMF to write the data to the UDMF data channel, and calls UDMF **updateData()** or **deleteData()** to update or delete the data saved by the application. The target application (data consumer) can access the data by the APIs provided by the UDMF. The UDMF manages the data lifecycle in a unified manner and deletes the data that has been stored for more than one hour every hour. 15 16Avoid using **unifiedDataChannel** APIs in multi-threaded calls. 17 18The unified data object (**UnifiedData**) is uniquely identified by a URI in the UDMF data channel. The URI is in the **udmf://*intention*/*bundleName*/*groupId*** format, where: 19 20+ **udmf**: protocol used to provide the data channel. 21 22+ *intention*: an enum of the data channel types supported by the UDMF. 23 24+ *bundleName*: bundle name of the data source application. 25 26+ *groupId*: group ID used for batch data management. 27 28Currently, the UDMF provides the public data channel for cross-application data sharing. 29 30The public data channel is a data channel shared by applications. All applications can write data to the channel. The data writer can update, delete, and query data based on the unique identifier generated when the data is written. The data reader can read only the full data in the data channel. The intention type of the public data channel is **DATA_HUB**. 31 32## Available APIs 33 34The following table lists the UDMF APIs. All of them are executed asynchronously in callback or promise mode. In the following table, callback-based APIs are used as an example. For details about more APIs and their usage, see [Unified Data Channel](../reference/apis-arkdata/js-apis-data-unifiedDataChannel.md) and [Standard Data Definition and Description](../reference/apis-arkdata/js-apis-data-uniformTypeDescriptor.md). 35 36| API | Description | 37|-----------------------------------------------------------------------------------------|---------------------------------------------| 38| insertData(options: Options, data: UnifiedData, callback: AsyncCallback\<string>): void | Inserts data to the UDMF public data channel. A unique data identifier is returned.| 39| updateData(options: Options, data: UnifiedData, callback: AsyncCallback\<void>): void | Updates the data in the UDMF public data channel. | 40| queryData(options: Options, callback: AsyncCallback\<Array\<UnifiedData>>): void | Queries data in the UDMF public data channel. | 41| deleteData(options: Options, callback: AsyncCallback\<Array\<UnifiedData>>): void | Deletes data from the UDMF public data channel. The deleted data set is returned.| 42 43 44## How to Develop 45 46The following example describes how to implement many-to-many data sharing. The data provider calls **insertData()** provided by the UMDF to write data to the public data channel. The return value (unique identifier of the data written) can be used to update or delete the data. The data consumer uses the query() APIs provided by the UDMF to obtain full data of the public data channel. 47 48### Data Provider 49 501. Import the **unifiedDataChannel** and **uniformTypeDescriptor** modules. 51 52 ```ts 53 import { unifiedDataChannel, uniformTypeDescriptor } from '@kit.ArkData'; 54 ``` 552. Create a **UnifiedData** object and insert it into the UDMF public data channel. 56 57 ```ts 58 import { BusinessError } from '@kit.BasicServicesKit'; 59 let plainText = new unifiedDataChannel.PlainText(); 60 plainText.textContent = 'hello world!'; 61 let unifiedData = new unifiedDataChannel.UnifiedData(plainText); 62 63 // Specify the type of the data channel to which the data is to be inserted. 64 let options: unifiedDataChannel.Options = { 65 intention: unifiedDataChannel.Intention.DATA_HUB 66 } 67 try { 68 unifiedDataChannel.insertData(options, unifiedData, (err, key) => { 69 if (err === undefined) { 70 console.info(`Succeeded in inserting data. key = ${key}`); 71 } else { 72 console.error(`Failed to insert data. code is ${err.code},message is ${err.message} `); 73 } 74 }); 75 } catch (e) { 76 let error: BusinessError = e as BusinessError; 77 console.error(`Insert data throws an exception. code is ${error.code},message is ${error.message} `); 78 } 79 ``` 803. Update the **UnifiedData** object inserted. 81 82 ```ts 83 let plainTextUpdate = new unifiedDataChannel.PlainText(); 84 plainTextUpdate.textContent = 'How are you!'; 85 let unifiedDataUpdate = new unifiedDataChannel.UnifiedData(plainTextUpdate); 86 87 // Specify the URI of the UnifiedData object to update. 88 let optionsUpdate: unifiedDataChannel.Options = { 89 //The key here is an example and cannot be directly used. Use the value in the callback of insertData(). 90 key: 'udmf://DataHub/com.ohos.test/0123456789' 91 }; 92 93 try { 94 unifiedDataChannel.updateData(optionsUpdate, unifiedDataUpdate, (err) => { 95 if (err === undefined) { 96 console.info('Succeeded in updating data.'); 97 } else { 98 console.error(`Failed to update data. code is ${err.code},message is ${err.message} `); 99 } 100 }); 101 } catch (e) { 102 let error: BusinessError = e as BusinessError; 103 console.error(`Update data throws an exception. code is ${error.code},message is ${error.message} `); 104 } 105 ``` 1064. Delete the **UnifiedData** object from the UDMF public data channel. 107 108 ```ts 109 // Specify the type of the data channel whose data is to be deleted. 110 let optionsDelete: unifiedDataChannel.Options = { 111 intention: unifiedDataChannel.Intention.DATA_HUB 112 }; 113 114 try { 115 unifiedDataChannel.deleteData(optionsDelete, (err, data) => { 116 if (err === undefined) { 117 console.info(`Succeeded in deleting data. size = ${data.length}`); 118 for (let i = 0; i < data.length; i++) { 119 let records = data[i].getRecords(); 120 for (let j = 0; j < records.length; j++) { 121 if (records[j].getType() === uniformTypeDescriptor.UniformDataType.PLAIN_TEXT) { 122 let text = records[j] as unifiedDataChannel.PlainText; 123 console.info(`${i + 1}.${text.textContent}`); 124 } 125 } 126 } 127 } else { 128 console.error(`Failed to delete data. code is ${err.code},message is ${err.message} `); 129 } 130 }); 131 } catch (e) { 132 let error: BusinessError = e as BusinessError; 133 console.error(`Delete data throws an exception. code is ${error.code},message is ${error.message} `); 134 } 135 ``` 136 137### Data Consumer 138 1391. Import the **unifiedDataChannel** and **uniformTypeDescriptor** modules. 140 141 ```ts 142 import { unifiedDataChannel, uniformTypeDescriptor } from '@kit.ArkData'; 143 ``` 1442. Query the full data in the UDMF public data channel. 145 146 ```ts 147 import { BusinessError } from '@kit.BasicServicesKit'; 148 // Specify the type of the data channel whose data is to be queried. 149 let options: unifiedDataChannel.Options = { 150 intention: unifiedDataChannel.Intention.DATA_HUB 151 }; 152 153 try { 154 unifiedDataChannel.queryData(options, (err, data) => { 155 if (err === undefined) { 156 console.info(`Succeeded in querying data. size = ${data.length}`); 157 for (let i = 0; i < data.length; i++) { 158 let records = data[i].getRecords(); 159 for (let j = 0; j < records.length; j++) { 160 if (records[j].getType() === uniformTypeDescriptor.UniformDataType.PLAIN_TEXT) { 161 let text = records[j] as unifiedDataChannel.PlainText; 162 console.info(`${i + 1}.${text.textContent}`); 163 } 164 } 165 } 166 } else { 167 console.error(`Failed to query data. code is ${err.code},message is ${err.message} `); 168 } 169 }); 170 } catch(e) { 171 let error: BusinessError = e as BusinessError; 172 console.error(`Query data throws an exception. code is ${error.code},message is ${error.message} `); 173 } 174 ``` 175