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Dynamic Pages with SlotKey and RenderContext

This is the default dynamic rendering pattern in SimplyPages.

SlotKey/Slot values also work with direct Component.render(context), but template-wrapped rendering is the preferred reuse pattern for stable structures.

Define Slots and a Template Once

public final class ArticleView {
    public static final SlotKey<String> ARTICLE_TITLE = SlotKey.of("article_title");
    public static final SlotKey<String> ARTICLE_BODY = SlotKey.of("article_body");

    public static final Template ARTICLE_TEMPLATE = Template.of(
        ContentModule.create()
            .withModuleId("article-view")
            .withTitle("Article")
            .withCustomContent(
                new Div()
                    .withChild(new HtmlTag("h2").withInnerText(ARTICLE_TITLE))
                    .withChild(new Paragraph().withChild(Slot.of(ARTICLE_BODY)))
            )
    );

    private ArticleView() {}
}

Template.of(...) and component.compile() are equivalent compile paths.

Render Per Request Using Context

@GetMapping("/articles/{id}")
@ResponseBody
public String article(@PathVariable String id) {
    Article article = articleService.load(id);

    RenderContext ctx = RenderContext.builder()
        .with(ArticleView.ARTICLE_TITLE, article.title())
        .with(ArticleView.ARTICLE_BODY, article.body())
        .build();

    return ArticleView.ARTICLE_TEMPLATE.render(ctx);
}

Request Mechanics

• Browser sends GET /articles/{id}.
• Controller loads article data.
• Controller maps fields into RenderContext.
• Template resolves slots and returns HTML.

Compile Policy for Reused Contexts

Use COMPILE_ON_FIRST_HIT only when you intentionally reuse a mutable context object.

RenderContext ctx = RenderContext.builder()
    .withPolicy(RenderContext.RenderPolicy.COMPILE_ON_FIRST_HIT)
    .with(ArticleView.ARTICLE_TITLE, article.title())
    .with(ArticleView.ARTICLE_BODY, article.body())
    .build();

If you later call ctx.put(key, newValue), compiled value for that key is replaced by live entry.

Anti-Pattern

Do not rebuild entire page/module trees on every dynamic update if only data changed.

Use stable templates + slots for data churn.

Do not share and mutate the same component/module instance concurrently across requests.