Module io.github.chkrishnatej.rp3200

Package io.github.chkrishnatej.rp3200

package io.github.chkrishnatej.rp3200

Receipt printing for the TVS RP 3200 Lite (and other ESC/POS thermal printers) from a Java server - typically a Spring Boot web application.

The library only produces bytes. It has no dependencies, does no I/O and never talks to a printer. The bytes are sent to the browser, which forwards them to the small rp3200-agent running on the shop PC that has the USB printer:

 Spring Boot + rp3200-core  --bytes-->  browser (rp3200-print.js)  --HTTP-->  rp3200-agent (127.0.0.1:9632)  --USB-->  printer
 

Two ways to describe a receipt

APIs

API	Use when
ReceiptTemplate	the layout lives in a text file (src/main/resources/receipts/*.txt) and is filled with data - recommended for bills, KOTs, tokens
EscPosBuilder	the receipt is assembled in Java code, or a template needs dynamic extras

Both produce identical bytes for the same layout and can be mixed with ReceiptTemplate.renderInto(EscPosBuilder, Object).

Quick start

 // 1. Template (compile once, e.g. as a Spring bean)
 ReceiptTemplate bill = ReceiptTemplate.fromClasspath("receipts/bill.txt");
 byte[] bytes = bill.render(data, PrinterProfile.RP3200_80MM);

 // 2. Builder
 byte[] bytes = new EscPosBuilder(PrinterProfile.RP3200_80MM)
         .center().bold(true).line("MY SHOP").bold(false)
         .left().row(Columns.parse("*,10r"), "Tea x2", "40.00")
         .cut()
         .build();
 

Browser side

The jar also contains META-INF/resources/rp3200/rp3200-print.js, which Spring Boot serves automatically at /rp3200/rp3200-print.js:

 <script src="/rp3200/rp3200-print.js"></script>
 <script>
   const printer = new RP3200Printer();                  // agent on http://127.0.0.1:9632
   await printer.printFromUrl('/api/bills/42/receipt');   // GET bytes from your server, print them
 </script>
 

Types in this package

• EscPosBuilder - fluent receipt builder
• PrinterProfile - paper width and character set
• Columns - table column layouts
• Align, TextSize, Style - formatting

Remote monitoring

rp3200-print.js can post the agent's health to your server; bind it with the records in io.github.chkrishnatej.rp3200.health (PrinterHealthReport, AgentStatus).

Requires Java 17 or newer. All types are either immutable and thread-safe (PrinterProfile, Columns, Style, ReceiptTemplate) or meant for one receipt on one thread (EscPosBuilder).

Related Packages

Package	Description
io.github.chkrishnatej.rp3200.health	Types for remote printer monitoring: what a shop PC's print agent reports about itself.
io.github.chkrishnatej.rp3200.template	Text templates for receipts: {{placeholders}} for data plus [markup] for formatting, compiled once and rendered to ESC/POS bytes.

Class	Description
Align	Horizontal alignment of a printed line (ESC/POS command ESC a n).
Columns	A column layout for table-like rows such as Item | Qty | Amount.
EscPosBuilder	Fluent builder that produces the raw ESC/POS bytes for one receipt.
PrinterProfile	Describes the physical printer: how many characters fit on a line and how text is encoded.
Style	Character style: bold, underline, reverse (white on black) and size.
Style.Segment	A run of text printed in one style - the building block of mixed-style table cells.
TextSize	Character magnification (ESC/POS command GS ! n).