Value slots, preencoded control flow, and bytecode codegen

[BernardoPe]

This PR adds value slots and preencoded control flow as a faster alternative to dynamic(), and adds bytecode generation for simple chains.

Value slots (textOf, rawOf, intOf, longOf, doubleOf, boolOf, attrOf, attrOfNullable) let a view read a single value from the model without creating a dynamic() block. The preprocessor stores each slot directly in the chain, so rendering does not need to resolve it as a dynamic block each time.

The same idea is used for forEachOf and whenOf. Their bodies are preencoded once as separate sub-chains, then reused during rendering.

For chains made up of static blocks and value slots, HtmlFlow can also generate a small class that writes directly to the output buffer. This removes the interpretation loop and avoids boxing for numeric slots. The generated bytecode is written directly, so this does not add a bytecode library dependency. If a chain cannot be compiled, it keeps using the interpreted version. Both paths produce the same output.

The changes also work with async views and hot reload.

template-benchmark when adapting the presentations and stocks views to use these features (tested locally):

Here is what the views look like:

public class StocksHtmlFlowSlots {

    public static HtmlView<List<Stock>> view = HtmlFlow.view(StocksHtmlFlowSlots::templateStocks);

    record StockDto(Stock stock, int index) {
        String rowClass()    { return index % 2 == 0 ? "even" : "odd"; }
        String symbol()      { return stock.getSymbol(); }
        String symbolHref()  { return "/stocks/" + stock.getSymbol(); }
        String url()         { return stock.getUrl(); }
        String name()        { return stock.getName(); }
        double price()       { return stock.getPrice(); }
        double change()      { return stock.getChange(); }
        double ratio()       { return stock.getRatio(); }
        String changeClass() { return change() < 0 ? "minus" : null; }
        String ratioClass()  { return ratio() < 0 ? "minus" : null; }
    }

    private static void templateStocks(HtmlPage view) {
        view
            .html()
                .head()
                    // ... unchanged head: title, meta, link, script, style ...
                .__()
                .body()
                    .h1().raw("Stock Prices").__()
                    .table()
                        .thead()
                            .tr()
                                .th().raw("#").__()
                                .th().raw("symbol").__()
                                .th().raw("name").__()
                                .th().raw("price").__()
                                .th().raw("change").__()
                                .th().raw("ratio").__()
                            .__()
                        .__()
                        .tbody()
                        .forEachOf(StocksHtmlFlowSlots::rows, tbody -> tbody
                            .tr()
                                .attrOf("class", StockDto::rowClass)
                                .td()
                                    .intOf(StockDto::index)
                                .__()
                                .td()
                                    .a()
                                        .attrOf("href", StockDto::symbolHref)
                                        .rawOf(StockDto::symbol)
                                    .__()
                                .__()
                                .td()
                                    .a()
                                        .attrOf("href", StockDto::url)
                                        .rawOf(StockDto::name)
                                    .__()
                                .__()
                                .td()
                                    .strong()
                                        .doubleOf(StockDto::price)
                                    .__()
                                .__()
                                .td()
                                    .attrOfNullable("class", StockDto::changeClass)
                                    .doubleOf(StockDto::change)
                                .__()
                                .td()
                                    .attrOfNullable("class", StockDto::ratioClass)
                                    .doubleOf(StockDto::ratio)
                                .__()
                            .__())
                        .__()
                    .__()
                .__()
            .__();
    }

    private static List<StockDto> rows(List<Stock> stocks) {
        return IntStream.range(0, stocks.size())
            .mapToObj(i -> new StockDto(stocks.get(i), i + 1))
            .toList();
    }
}

public class PresentationsHtmlFlowSlots {

    public static HtmlView<Iterator<Presentation>> view =
        HtmlFlow.view(PresentationsHtmlFlowSlots::presentationsView);

    private static void presentationsView(HtmlPage view) {
        view.html()
            .head()
                // ... unchanged head: meta, title, link ...
            .__()
            .body()
                .div().attrClass("container")
                    .div().attrClass("page-header")
                        .h1().raw("JFall 2013 Presentations - htmlApi").__()
                    .__()
                    .forEachOf(PresentationsHtmlFlowSlots::all, div -> div
                        .div().attrClass("panel panel-default")
                            .div().attrClass("panel-heading")
                                .h3()
                                    .attrClass("panel-title")
                                    .rawOf(PresentationsHtmlFlowSlots::heading)
                                .__()
                            .__()
                            .div()
                                .attrClass("panel-body")
                                .rawOf(Presentation::getSummary)
                            .__()
                        .__()
                    )
                .__()
                .script().attrSrc("/webjars/jquery/3.1.1/jquery.min.js").__()
                .script().attrSrc("/webjars/bootstrap/3.3.7-1/js/bootstrap.min.js").__()
            .__()
        .__();
    }

    private static Iterable<Presentation> all(Iterator<Presentation> iter) {
        return () -> iter;
    }

    private static String heading(Presentation p) {
        return p.getTitle() + " - " + p.getSpeakerName();
    }
}

Depends on

This depends on xmlet/xsd2poet#2, which adds the slot methods and Slot<M> to the generated element API.

For now, this branch uses xsd2poet-java:1.0.9-SNAPSHOT, built locally.

[github-actions]

Please run mvn spotless:apply locally to fix the formatting issues, then commit and push the changes.