Touch UI dropdown from JSON file/Servlet

Populate Touch UI Dropdown options from JSON file or Servlet which returns JSON
In AEM classic UI, the selection/dropdown widget's options can be populated using JSON response(via JSON file or servlet) but in Touch UI, you need to write a piece of code to achieve the same. This blog is about a utility which populates dropdown options dynamically from a JSON file which presents in the repository or from the servlet JSON response.

Custom Utility to populate a dropdown
This custom java utility populates touch UI dropdown from JSON data.

Steps are as follows:
Create a dropdown using granite/coral select type and create datasource node under the select node.
Add following properties to datasource node :
- options (String) - path of json file or Servlet, which returns json examples : /apps/commons/utils/json/dropdown/color.json /bin/utils/json/dropdown/style - sling:resourceType (String) - utils/granite/components/select/datasource/json- repoSource (Boolean) - optional property to specify file in repository or servlet json source.
true(Default) : to read JSON file stored in repository
false : to get JSON from another Servlet

if repoSource property is true JSON file will be read using Node API, if false then another HTTP call is to be made to get JSON response either from json file or servlet.
if repoSource is false it works in both cases in file or servlet JSON response. This property is just added to avoid unnecessary HTTP call if the file is in the repository.

datasource node properties

You can find the example that explains how to use datasource with to populate touch UI dropdown at https://helpx.adobe.com/experience-manager/using/creating-granite-datasource.html

Utility Servlet code
https://github.com/arunpatidar02/aem63app-repo/blob/master/java/dropdown/PopulateTouchUIDropdownFromJsonResource.java

POM file changes
Add below dependencies in parent and core pom(if not already added)

1. GSON
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.5</version>
</dependency>

2. HTTP Client
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.5</version>
</dependency>

Example JSON file/response
The Josn response can have array of options in below formates:
{"text": "White","value": "white"}
{"text": "White","value": "white","disabled": true} - to disable option in dropdown
{"text": "White","value": "white","selected": true} - to preselect option in dropdown

Example file -
https://github.com/arunpatidar02/aem63app-repo/blob/master/java/dropdown/sample.json

Conclusion:
This utility can be used to render any touch UI dropdown options from json source similar to classic UI. This Utility uses GSON to parse JSON and create options. If you are looking for same using JSONObject API, you can check example at https://github.com/arunpatidar02/aem63app-repo/blob/master/java/DatasourceJson.java