#125: IHKExporter.java

Excel report generator for IHK apprenticeship weekly reports. The core logic of the plugin — takes a week's timesheet entries, the trainee's configuration (IHKCommentObject), and a Merlin Excel template, and produces a formatted IHK-compliant .xlsx file. 292 lines of Java.

Architecture

Uses Merlin (Micromata's Excel templating engine, see #221+) — loads an .xlsx template from the classpath (ClassPathResource("merlin/ihk/ihk.xlsx")), fills in data programmatically, and returns a ByteArrayOutputStream for download.

Key data flows

1. Training year calculation: Period.between(ausbildungsbeginn, now).getYears() → auto-calculates the training year unless ausbildungsjahr is manually set
2. Timesheet filtering: queries TimesheetDO for the trainee's entries in the selected week, grouped by day
3. Hours aggregation: sums work hours per day, formats with DecimalFormat("0.00")
4. Excel population via Merlin:
   • Reads template workbook from merlin/ihk/ihk.xlsx
   • Fills header: trainee name, department (teamname), training year, calendar week, date range
   • Fills daily rows: day of week, date, topic/activity description from timesheet, hours worked, signature placeholders
   • Applies cell formatting: borders, font sizes, merged cells for header block
5. Output: writes the populated workbook to a ByteArrayOutputStream, returns the byte array for HTTP download with filename Berichtsheft_KW{week}_{name}.xlsx

Excel template structure

The IHK requires a specific report format containing:

• Header: company name, trainee name, training year, calendar week, date range
• Department/supervisor section
• Daily rows: topics/activities performed, work hours, signature fields
• Weekly summary row with total hours
• Signature sections for trainee and supervisor

The Merlin template (ihk.xlsx) contains these structural elements; the exporter fills in the dynamic data.

Dependencies

• de.micromata.merlin.excel.* — Merlin Excel API for template-based Excel generation
• TimesheetDO — timesheet entries with description, start/stop time, date
• PFDateTime, PFDay, LocalDate — date/time handling for week boundaries
• JsonUtils — deserializes IHKCommentObject from address comment
• AddressDO / ThreadLocalUserContext.getLoggedInUser() — fetches trainee contact for config