This Java application demonstrates how to interact with a web API, retrieve data from various endpoints, and store the data in Excel format using Java IO. Additionally, it includes JUnit tests for the conversion process.

• Main Method: main(String[] args)
  • Takes user input for the resulting Excel file name.
  • Defines an array of Endpoint objects representing different API endpoints.
  • Retrieves data from each endpoint, converts the JSON response to Excel format, and saves it to the specified file.

• Attributes:
  • path: API endpoint path
  • queryParams: Query parameters for the endpoint
  • jsonKey: Key to extract data array from JSON response
  • sheetName: Name of the Excel sheet to be created

• Methods:
  • convert(String jsonInput, String filename, String dataArrayKey, String sheetName)
    • Converts JSON data to Excel format and saves it to a file.
  • getOrCreateWorkbook(String filename)
    • Checks if the Excel file exists; if yes, opens it; if not, creates a new workbook.
  • verifySheetDoesNotExist(Workbook workbook, String sheetName)
    • Throws an exception if a sheet with the same name already exists in the workbook.
  • extractDataArrayFromJson(String jsonInput, String dataArrayKey)
    • Extracts the data array from the JSON response.
  • createAndFillHeaderRow(Sheet sheet, JsonNode firstItem)
    • Creates and fills the header row in the Excel sheet.
  • populateSheetWithData(Sheet sheet, ArrayNode dataArray)
    • Populates the Excel sheet with data.
  • adjustColumnsWidth(Sheet sheet, int columnCount)
    • Adjusts the column widths in the Excel sheet.
  • writeFile(Workbook workbook, String filePath)
    • Writes the workbook to an Excel file.

• Test Methods:
  • testConvertWithNewFile()
    • Tests the conversion with a modified JSON content, checks the existence of the created Excel file, and validates the content.
  • testConvertWithExistingSheetName()
    • Tests the scenario where converting with an existing sheet name should throw an IllegalArgumentException.

• Methods:
  • doGetRequest(String endpointURL)
    • Sends a GET request to the specified API endpoint and returns the JSON response.
  • buildUrl(String path, String queryOptions)
    • Builds the complete URL for the API request.
  • getData(String endpointPath, String queryParams)
    • Retrieves data from the API using the specified endpoint path and query parameters.

• Test Methods:
  • testBuildUrl()
    • Tests the buildUrl method to ensure correct URL construction.