Rendering & data

Crema evaluates expressions against the data map you pass to view / render (and nested maps, lists, and bean-style getters). This page covers how values become HTML — escaped or raw — and the helpers that turn data into JSON, URLs, and translation strings. For making views from controllers, see the View helper.

Passing data

Every render starts with a Map<String, Any?> (Kotlin) or Map<String, ?> (Java). Keys become top-level names in the template:

Kotlin

view(
    "posts.show",
    mapOf(
        "title" to "Hello",
        "post" to post,
        "tags" to listOf("kona", "jvm"),
    ),
).render()

Java

Views.make(
    "posts.show",
    Map.of(
        "title", "Hello",
        "post", post,
        "tags", List.of("kona", "jvm")
    )
).render();

<h1>{{ title }}</h1>
<p>{{ post.body }}</p>

Nested paths use dots: post.body walks map keys or zero-arg getters (getBody(), isActive(), or a method/field named body).

View.with(key, value) / with(map) merges more keys before render(). Child contexts (includes, loops, components) inherit parent data and may overlay loop variables or slots.

Escaped echoes

{{ expr }} prints the value as text with HTML escaping for &, <, >, ", and ':

<p>Hello {{ name }}</p>
{{-- name = "<script>" → Hello &lt;script&gt; --}}

Empty or missing values render as an empty string — not the literal null.

Raw HTML

{!! expr !!} prints without escaping. Use only for trusted markup you built yourself (or already sanitized):

<div class="prose">{!! html !!}</div>

Unclosed {!! / {{ sequences are errors at render time.

Literal @ and comments

Syntax	Result
@@	A single @ in the output (useful when documenting directives)
{{-- … --}}	Comment — stripped before any other processing

{{-- Never appears in HTML --}}
<code>@@extends</code>

Expressions

Echoes and most directive arguments accept a small expression language:

Kind	Examples
Literals	true, false, null / nil, 42, 3.5, 'string', "string"
Comparisons	==, !=, <, >, <=, >= (numbers compare numerically; otherwise stringified)
Logic	and, or, not …, !…
Helpers	isset(name), empty(name)
Paths	user.name, errors.email

@if(count > 0 and ready)
  Ready
@endif

{{ isset(name) }}
{{ empty(items) }}
{{ not ok }}
{{ a == 1 or b == 2 }}

isset(path) is true when the resolved value is non-null. empty(path) is true when the value is not truthy (see truthiness).

There is no arbitrary code execution in templates — only this expression subset and property access.

@json

@json($expr) encodes a value as JSON (Jackson). Useful inside <script> or data attributes:

<script>
  window.bootstrap = @json($user);
</script>

Kotlin

crema.render(
    "page",
    mapOf("user" to mapOf("name" to "Ada", "id" to 1)),
)
// → window.bootstrap = {"name":"Ada","id":1};

Java

crema.render(
    "page",
    Map.of("user", Map.of("name", "Ada", "id", 1))
);
// → window.bootstrap = {"name":"Ada","id":1};

@lang

@lang('key') resolves a translation string. Crema prefers a lang map in the view data when present; otherwise it calls Lang.get from kona-support.

@lang('messages.welcome')
@lang('messages.hello', replace)

The optional second argument is an expression that evaluates to a Map of replacements. Placeholders in the string use :name form (Hi :name + name → Ada → Hi Ada).

Kotlin

crema.render(
    "greet",
    mapOf(
        "replace" to mapOf("name" to "Ada"),
        // or override a single key:
        // "lang" to mapOf("messages.hello" to "Hi :name"),
    ),
)

Java

crema.render(
    "greet",
    Map.of("replace", Map.of("name", "Ada"))
);

Register SupportServiceProvider (or call Lang.setTranslator) before rendering when you rely on the global translator.

@asset

@asset('css/app.css') builds a public URL. With no base in the data map it emits /css/app.css. Pass asset_url or assetUrl to prefix a CDN:

<link rel="stylesheet" href="@asset('css/app.css')" />

Leading slashes on the path argument are trimmed before joining.

@vite

@vite('resources/js/app.js') emits a script (or link) tag pointing at /build/.... Lists are supported:

@vite('resources/js/app.js')
@vite(['resources/js/app.js', 'resources/css/app.css'])

.css entries become <link rel="stylesheet">; everything else becomes <script type="module">. This helper is intentionally thin — it does not read a Vite manifest. For hot-reload and manifest resolution, see Vite / asset bundling and Inertia.

Edge cases

Situation	Behavior
Missing key in {{ name }}	Empty string
null / nil literal	Empty string when echoed
Nested null (user.name when user is null)	Empty string
Unclosed {{ or {!!	Render throws
Map vs bean	Maps use key lookup; other objects use getters / zero-arg methods / public fields

Next

• Layouts & inheritance — share HTML shells across pages
• Control structures — conditionals and loops over the same expressions
• Directive reference — full directive tables