Performance & SEO

Most of this is on by default — pages ship one small cached runtime instead of a framework bundle, and the server does the rendering.

SEO Metadata

One builder emits the title, description, canonical link, Open Graph, and Twitter card tags — all consistent from a single declaration.

head(
    metaCharset(), metaViewport(),
    Seo.of("JWeb — Java Web Framework",
           "Build complete web apps entirely in Java")
        .url("https://jweb.dev/")
        .image("https://jweb.dev/og.png")
        .siteName("JWeb")
        .render()
)

Image Optimization

Images are resized on the fly and cached immutably — no build step, no dependencies (ImageIO).

img("/jweb/img?src=/static/hero.jpg&w=800")

• src is restricted to classpath static/ and public/ resources
• w resizes to that width, keeping the aspect ratio (max 3840)
• Results are cached in memory and served with a 1-year immutable header

Asset Caching

The client runtime and prefetch script are served as external files with a content-hash version, so browsers cache them across every navigation and only the page HTML travels on each request.

<script src="/jweb/runtime.js?v=67f7c91e"></script>
Cache-Control: max-age=31536000, public, immutable

Streaming & Prefetch

• Streamed.of(() -> page) flushes the shell immediately and streams Suspense blocks as their data resolves (see Streaming SSR)
• Link prefetching warms pages on hover, so navigation feels instant
• A background warmup pre-renders registered pages at startup, so the first visitor doesn't pay lazy-initialization cost
• gzip compression is enabled for text responses

Secure Baseline

One call adds the production essentials — security headers, request IDs, and compression negotiation — to every route:

app.use(Middlewares.recommended());

Request IDs, Logs and Traces

Every request has an id before anything sees it: the caller's X-Request-ID or a fresh one. The response carries it back, every log line of the request shows it, the error page quotes it. jweb.Trace opens a span around every route, SQL statement, job, PubSub delivery, mail, Fetch and browser event; add the actuator and they become Micrometer observations, add micrometer-tracing and they are spans in the request's trace.

import jweb.Trace;
import jweb.Middlewares;

record Order(long id) {}
Order order = new Order(9);

String id = req.id();                         // the same id on the response, in the logs, on the error page
app.use(Middlewares.logging());               // GET /orders/9 200 12ms

try (Trace.Span span = Trace.span("order.price", "kind", "retail")) {   // tags at the start: low cardinality
    span.tag("order.id", order.id());                                     // tags later: high cardinality
}
Order priced = Trace.in("order.price", () -> order);