Quote PDFs in Spring Boot

Why quotes become PDFs

A quote is an offer with an expiry, and it gets forwarded to people who will never log into your product. It has to stand alone and it has to be fixed at the moment it was sent. That is the difference between a document and a view of a database, and it is why sales teams keep asking for this.

What a quote has to carry

Before any of the code below matters, the template has to produce a document that is actually a quote. These are the fields that make it one, and the ones a reader or an auditor will look for first.

• a quote reference, which the eventual order will cite
• the validity date, after which the pricing no longer stands
• each line with the price offered, which may not be list price
• any discount shown as a discount rather than folded into the unit price
• the terms attached to the offer: payment schedule, lead time, exclusions

Turning your Thymeleaf template into a document

You already have the markup. TemplateEngine.process("invoice", context) gives you it as a string, which is the only input the render needs. Thymeleaf's @{...} link syntax resolves against the servlet context path. In a rendered document that context does not exist, so build absolute URLs or inline the CSS.

The Spring Boot implementation

java.net.http.HttpClient ships with the runtime, so this adds no dependency. The render happens in a controller returning StreamingResponseBody, and you return ResponseEntity<StreamingResponseBody>.

// QuotePdfController.java
package com.example.quotes;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Duration;

@RestController
public class QuotePdfController {

  private final HttpClient http = HttpClient.newHttpClient();
  private final TemplateEngine templates;

  @Value("${pdfpipe.key}")
  private String apiKey;

  @GetMapping(value = "/quotes/{id}.pdf", produces = MediaType.APPLICATION_PDF_VALUE)
  public ResponseEntity<StreamingResponseBody> pdf(@PathVariable String id) throws Exception {
    Context context = new Context();
    context.setVariable("quote", quoteService.find(id));
    String html = templates.process("quote", context);

    String body = new ObjectMapper().writeValueAsString(Map.of(
        "html", html,
        "options", Map.of("format", "A4", "printBackground", true)));

    HttpRequest request = HttpRequest.newBuilder(URI.create("https://api.pdfpipe.xyz/v1/pdf"))
        .header("Authorization", "Bearer " + apiKey)
        .header("Content-Type", "application/json")
        .timeout(Duration.ofSeconds(60))
        .POST(HttpRequest.BodyPublishers.ofString(body))
        .build();

    // ofInputStream, not ofByteArray. A long quote on the heap is how a
    // container sized for JSON payloads meets the garbage collector.
    HttpResponse<InputStream> upstream =
        http.send(request, HttpResponse.BodyHandlers.ofInputStream());

    return ResponseEntity.ok()
        .header("Content-Disposition", "attachment; filename=\"quote-" + id + ".pdf\"")
        .body(out -> upstream.body().transferTo(out));
  }
}

The CSS that makes a quote page correctly

The layout problem specific to this document is that optional line items and discount blocks make the length unpredictable, so the signature area must not orphan onto a page of its own. These rules handle it.

/* Backgrounds are dropped unless printBackground is set on the
   request, which is the usual reason a document renders in plain
   black and white when it looked right in the browser. */
@page {
  size: A4;
  margin: 18mm 16mm;
}

table { break-inside: avoid; }
h2    { break-after: avoid; }

What goes wrong in Spring Boot

RestTemplate returning byte[] materialises the whole document on the heap, and a servlet container sized for JSON will meet the garbage collector after a handful of concurrent report renders. Use the reactive client or the JDK client with ofInputStream.

What people try first

Most Spring Boot projects reach for Flying Saucer, which renders XHTML strictly and rejects markup a browser would accept, or iText, whose AGPL licence makes commercial use a paid decision. That works until it is running on more than one machine, at which point the browser becomes the thing you operate rather than the thing you use.

Where the quote lives afterwards

Rendering is the short part. A quote is dead once it expires or converts, so retention is short and driven by the sales system rather than by law. What matters is that the version the customer received is the one you can produce later, because a disputed price is settled by the document that was sent.

Getting the document right

• Check the validity date, since a quote without one is an open-ended commitment.
• Generation is triggered by a salesperson sending it, so latency is felt directly by a person waiting, so size the timeout for that path rather than for a health check.
• These are produced one at a time by a person who is waiting, so latency is felt directly.
• Backgrounds are painted by default here, so a design that uses colour needs nothing set. Only an explicit print_background of false turns them off.

Frequently asked

Related

Other Spring Boot documents, and the same quote in other stacks.