usecase ยท Aug 13, 2020

Automate Excel Sheet Processing with Java

Hawk Chen
Developer, Keikai.

A Sheet Processing Use Case

My colleague Penny in the HR department has to do a routine task each month: making payroll sheets for everyone in the company. There is a sheet containing a table of all employees with salary information:

This is how the summary report looks like:

And she has to create payroll sheets for each person on the list based on the template sheet:

To avoid copying cell by cell manually, I create a web application with Keikai to read salary data row by row and produce payroll sheets. The whole process is:

Import a Pre-designed Excel File

I create a Keikai spreadsheet by writing tags and attributes in a zul of ZK Framework which is a UI framework based on Java EE. By specifying at src attribute with a file path, Keikai can import my Payroll.xlsx.

<spreadsheet height="100%" width="100%" src="/WEB-INF/books/Payroll.xlsx"
                 maxVisibleColumns="15" maxVisibleRows="20"
                 hidecolumnhead="false"  hiderowhead="false"
                 showToolbar="true" showSheetbar="true" showFormulabar="true"
                 apply="io.keikai.devref.usecase.PayrollComposer"/>

When I visit the zul with a browser, Keikai renders the file:

The ZK framework will parse the zul page above and instantiate a Keikai Java object(Spreadsheet) for us to control.

Controller

Then I also create a Java controller, PayrollComposer to access the Keikai Java object and apply the controller on the page at apply attribute: apply="io.keikai.devref.usecase.PayrollComposer"

Named Range

I make a cell like a button on the sheet. When I click the cell, Keikai will start to produce payroll sheets. I give a name, Generate, to the cell.

After that, I can create a Range object (generateButton) with the name:

generateButton = Ranges.rangeByName(sheet, "Generate");

Here is the related code snippet:

public class PayrollComposer extends SelectorComposer<Component>{

    @Wire("spreadsheet")
    private Spreadsheet spreadsheet;
    final private static String EMPLOYEE_SHEET = "Payroll";
    private Range generateButton;
    private Sheet sheet;

    @Override
    public void doAfterCompose(Component comp) throws Exception {
        super.doAfterCompose(comp);
        sheet = spreadsheet.getBook().getSheet(EMPLOYEE_SHEET);
        generateButton = Ranges.rangeByName(sheet, "Generate");
    }
...

Listen to Button Clicking

Then I register an event listener for the cell (button) clicking by @Listen and check whether the button generateButton is clicked or not:

    @Listen(Events.ON_CELL_CLICK + "=spreadsheet")
    public void onCellClick(CellMouseEvent e) {
        String sheetName = e.getSheet().getSheetName();
        switch (sheetName) {
            case EMPLOYEE_SHEET:
                if (RangeHelper.isRangeClicked(e, generateButton))
                    fillPayrollSlips();
                break;
        }
    }

When the button is clicked, it just starts to fill the payroll slips.

Fill payroll data into sheets

Before filling a payroll sheet, I have to read all employees' salary data row by row from the table. The table also has a corresponding named range, PayrollTable, that I don't need to hard code its cell address.

private void fillPayrollSlips() {
    String tableName = "PayrollTable";
    Range payrollRange = Ranges.rangeByName(sheet, tableName);
    List<Map<String, Object>> employeeSalaries = getEmployeeSalaries(payrollRange);
    generateAllPayrollSlips(employeeSalaries);
}

To avoid filling data into a fixed cell address of the payroll sheet, I create a named range for each field that maps the corresponding column name.

Column Name <==> Named Range

Hence, I can fill data in a simple loop. Just clone (cloneSheet()) the template sheet and fill each field by the named range.

    private void generateAllPayrollSlips(List<Map<String, Object>> employeeSalaries) {
        for (Map<String, Object> employee : employeeSalaries) {
            Sheet payrollSheet = Ranges.range(spreadsheet.getBook().getSheet("Form"))
                    .cloneSheet((String) employee.get("Name"));
            for (String field : employee.keySet()) {
                Ranges.rangeByName(payrollSheet, field).setCellValue(employee.get(field));
            }
        }
    }

With the named range, I don't need to hard code a cell address in the code, which makes the code more robust against sheet layout change.

Source Code

I was able to turn this manual Excel copy-pasting task into an automated task in less than 100 lines. I hope you find this example interesting. You can find out the complete code at Github.