# View Templates Configuration In SunbirdRC we can configure view templates (JSON transformers) which can be applied during runtime. It supports enabling/disabling properties in JSON responses. It also provides executing simple [JEXL](https://commons.apache.org/proper/commons-jexl/) expressions and also supports creating custom provider functions. Below is an example of a view template: ```json { "id": "personDefaultView1", "subject": "Person", "fields": [ { "name": "firstName", "title": "NAME" }, { "name": "lastName", "display": true }, { "name": "nationalIdentifier", "title": "OS number", "display": false, "$comment": "This field is not displayable, but needed for internal referencing" }, { "title": "Name in passport", "function": "#/functionDefinitions/concat($lastName, $firstName)", "$comment": "This is a virtual field not defined in the schema" }, { "title": "Name as in DL", "function": "#/functionDefinitions/userDefinedConcat($firstName, $lastName)", "$comment": "This is a virtual field not defined in the schema" } ], "functionDefinitions": [ { "name" : "concat", "result": "arg1 + \", \" + arg2", "$comment": "arg1 and arg2 will be populated with parameter values at runtime" }, { "name" : "userDefinedConcat", "provider": "dev.sunbirdrc.provider.SampleViewFunctionProvider", "$comment" : "Complex operations that cannot be expressed easily in an in-line function definition can be implemented as a class. " } ] } ``` When the above template is applied for the below response payload: ```json { "Person": { "nationalIdentifier": "nid823", "firstName": "Ram", "lastName": "Moorthy", "gender": "MALE", "dob": "1990-12-10" } } ``` The response will be transformed to: ```json { "Person": { "NAME": "Ram", "lastName": "Moorthy", "Name in passport": "Moorthy, Ram", "Name as in DL": "Ram : Moorthy" } } ``` The view templates support configuring what fields should be displayed, changing the field names, and also performing functionalities on top of the fields. In the above template, a field called `firstName` which is present in the entity is been renamed to `NAME.` ```json { "name": "firstName", "title": "NAME" } ``` By default, all fields defined in the template are treated to be `"display": true`. If the fields are not supposed to be displayed then we can set `"display": false` ```json { "name": "nationalIdentifier", "title": "OS number", "display": false, "$comment": "This field is not displayable, but needed for internal referencing" } ``` We can also define expressions or custom functions to perform complex/custom transformations. ```json { "name" : "concat", "result": "arg1 + \", \" + arg2", "$comment": "arg1 and arg2 will be populated with parameter values at runtime" }, ``` In the above example, a custom JEXL expression to concatenate two fields is inline defined in the view template. ```json { "title": "Name in passport", "function": "#/functionDefinitions/concat($lastName, $firstName)", "$comment": "This is a virtual field not defined in the schema" }, ``` The above code illustrates on how to call the inline-defined functions for a specific field. We can also write Java code which can be used to perform custom/complex operations and also execute that in the view template. ```json { "name" : "userDefinedConcat", "provider": "dev.sunbirdrc.provider.SampleViewFunctionProvider", "$comment" : "Complex operations that cannot be expressed easily in an in-line function definition can be implemented as a class. " } ``` The implementation of the above provider is here, A custom provider function should implement `IViewFunctionProvider` Similarly, SunbirdRC is shipped with another provider functions that can be used for transformation,\ [RemovePathFunctionProvider](https://github.com/Sunbird-RC/sunbird-rc-core/blob/3dcca8a7ca6be355991808a0d1ebfc3a824c43c5/java/view-templates/src/main/java/dev/sunbirdrc/provider/RemovePathFunctionProvider.java)\ The above provider function will remove JSON paths from a nested object.\ Example to demonstrate how to use the above function, ```json { "subject": "Reporter", "fields": [ { "name": "name", "title": "name", "display": true }, { "name": "address", "title": "address", "function": "#/functionDefinitions/removePath($address, $.line)", "display": true } ], "functionDefinitions": [ { "name" : "removePath", "provider": "dev.sunbirdrc.provider.RemovePathFunctionProvider" } ] } ``` The above template will transform the below response payload ```json { "Person": { "nationalIdentifier": "nid823", "name": "Ram", "lastName": "Moorthy", "gender": "MALE", "dob": "1990-12-10", "address": { "line": "1st stree", "city": "bangalore" } } } ``` to the below format ```json { "Person": { "name": "Ram", "address": { "city": "bangalore" } } } ``` The view templates can be applied to both the GET APIs. We need to pass a `viewTemplateId` the header which contains the value of the view template file to be applied. {% content-ref url="../api-reference/registry/get-an-entity" %} [get-an-entity](https://docs.sunbirdrc.dev/~/changes/ADw6FieYgLmHh8a9Loem/api-reference/registry/get-an-entity) {% endcontent-ref %} {% content-ref url="../api-reference/registry/get-an-entity-by-id" %} [get-an-entity-by-id](https://docs.sunbirdrc.dev/~/changes/ADw6FieYgLmHh8a9Loem/api-reference/registry/get-an-entity-by-id) {% endcontent-ref %} Example: ```powershell curl --location 'localhost:8081/api/v1/StudentWithPassword/1-2ee0c034-0a81-4c7f-a971-058af35911cb' \ --header 'viewTemplateId: student_view_template.json' \ ``` View templates can be used in search/discovery APIs. The respective template id needs to be part of the request body as below ```json { "filters": { }, "viewTemplateId": "student_view_template.json" } ``` {% content-ref url="../api-reference/discovery-api/search-an-entity" %} [search-an-entity](https://docs.sunbirdrc.dev/~/changes/ADw6FieYgLmHh8a9Loem/api-reference/discovery-api/search-an-entity) {% endcontent-ref %}