Add pdf-invoice module: one invoice in OpenPDF 3.0.5, iText Core 9.8.0 and Flying Saucer 10.7.0, Devanagari shaping checked by rendering, streamed vs buffered download, subset sizes and timings

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b6Kg9RWSTJzyz6KP9X
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2026-10-30 16:46:25 +00:00
co-authored by Claude Sonnet 5.5
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| Directory | Article | What it demonstrates |
|---|---|---|
| [`pdf-invoice/`](pdf-invoice) | [Generate PDF Invoices in Spring Boot: OpenPDF vs iText vs Flying Saucer (HTML to PDF)](https://ankurm.com/spring-boot-generate-pdf-invoice-openpdf-itext-flying-saucer/) | one invoice rendered by OpenPDF 3.0.5, iText Core 9.8.0 (AGPL 3 or commercial) and Flying Saucer 10.7.0 from a Thymeleaf template, with embedded Noto Sans Devanagari: none of the three shapes Marathi/Hindi conjuncts by default (checked by rendering to PNG against a libraqm reference), OpenPDF's `GlyphLayoutManager` does but breaks text extraction until `ActualText` is on, OpenPDF's static `LayoutProcessor` is JVM-global and breaks other writers, Apache FOP on the classpath did not help, streamed vs buffered failure (`200` + curl exit 18 vs `500`), font subsetting, indicative per-invoice timings |
| [`excel-export/`](excel-export) | [Export Excel and CSV from Spring Boot: Streaming 1 Million Rows with Apache POI SXSSF](https://ankurm.com/spring-boot-export-excel-csv-streaming-poi-sxssf/) | XSSF vs SXSSF under a fixed 512 MB heap (XSSF out of memory between 50,000 and 100,000 rows and at 1,000,000 rows even with 3 GB), 1,000,000 rows streamed with `StreamingResponseBody` under a 64 MB heap, sheet rolling at 1,048,576 rows, `compressTempFiles` cutting the spill from 475 MB to 56 MB, OpenCSV swallowing write errors, and an SXSSF file LibreOffice will not open |
| [`thymeleaf-htmx/`](thymeleaf-htmx) | [Spring Boot 4 + Thymeleaf + htmx: Server-Side CRUD UI in 2026](https://ankurm.com/spring-boot-thymeleaf-htmx-crud-ui/) | one URL answering as full page or fragment on `HX-Request`, a Thymeleaf layout, 422 validation re-render, pagination, inline edit and delete, 10 MockMvc tests plus a headless-Chromium check that observed htmx 2 ignoring a 204 and (without a config tag) a 422 |
| [`rate-limit/`](rate-limit) | [Rate Limiting Spring Boot APIs with Bucket4j and Redis: Per-User, Per-Key and Global Limits](https://ankurm.com/spring-boot-rate-limiting-bucket4j-redis/) | per-user, per-API-key and global token buckets in a servlet filter on Bucket4j 8.21 (`bucket4j_jdk17-*`), `429` with `Retry-After` and `X-RateLimit-*` headers, two application instances sharing one Redis bucket and 200 concurrent requests letting exactly 20 through, a limit raised in `application.yml` that does not change buckets already stored in Redis until a config version is bumped, a client clock 30 s ahead handing out tokens another instance already spent, and fail-open versus fail-closed when Redis dies |