pug4j's intention is to be able to process pug templates in Java without the need of a JavaScript environment, while being fully compatible with the original pug syntax.
pug4j was formerly known as jade4j. Because of the naming change of the javascript version and the alignment to the featureset of pug.js (https://pugjs.org/) we decided to switch the name.
- Example
- Syntax
- Usage
- Simple static API
- Full API
- Expressions
- Reserved Words
- Framework Integrations
- Breaking Changes in 3.0.0
- Breaking Changes in 2.0.0
- Breaking Changes in 1.0.0
- Authors
- License
index.pug
doctype html
html
head
title= pageName
body
ol#books
for book in books
if book.available
li #{book.name} for #{book.price} €
Java model
List<Book> books = new ArrayList<Book>();
books.add(new Book("The Hitchhiker's Guide to the Galaxy", 5.70, true));
books.add(new Book("Life, the Universe and Everything", 5.60, false));
books.add(new Book("The Restaurant at the End of the Universe", 5.40, true));
Map<String, Object> model = new HashMap<String, Object>();
model.put("books", books);
model.put("pageName", "My Bookshelf");Running the above code through String html = Pug4J.render("./index.pug", model) will result in the following output:
<!DOCTYPE html>
<html>
<head>
<title>My Bookshelf</title>
</head>
<body>
<ol id="books">
<li>The Hitchhiker's Guide to the Galaxy for 5,70 €</li>
<li>The Restaurant at the End of the Universe for 5,40 €</li>
</ol>
</body>
</html>See also the original https://github.com/pugjs/pug#syntax.
Just add following dependency definitions to your pom.xml.
<dependency>
<groupId>de.neuland-bfi</groupId>
<artifactId>pug4j</artifactId>
<version>3.0.0-alpha-2</version>
</dependency>Clone this repository ...
git clone https://github.com/neuland/pug4j.git... build it using maven ...
cd pug4j
mvn install... and use the pug4j-2.x.x.jar located in your target directory.
The simple static API provides the easiest way to render templates in one step:
String html = Pug4J.render("./index.pug", model);With pretty printing:
String html = Pug4J.render("./index.pug", model, true);Streaming output using a java.io.Writer:
Pug4J.render("./index.pug", model, writer);Note: For production use with template reuse, use the Full API below which provides caching and more control.
For production use, create a PugEngine instance with the builder pattern. This separates template loading/caching (engine) from render-time settings (context).
Quick setup:
PugEngine engine = PugEngine.forPath("/templates/");
PugTemplate template = engine.getTemplate("index.pug");
String html = engine.render(template, model);Advanced configuration:
// Configure template loading
FileTemplateLoader loader = new FileTemplateLoader("/root/dir/");
loader.setBase("base/path");
// Build engine with settings
PugEngine engine = PugEngine.builder()
.templateLoader(loader)
.caching(true)
.build();
// Get template (cached automatically)
PugTemplate template = engine.getTemplate("index.pug");
// Prepare model
Map<String, Object> model = new HashMap<>();
model.put("company", "neuland");
// Render with default settings
String html = engine.render(template, model);
// Or with custom render context
RenderContext context = RenderContext.builder()
.prettyPrint(true)
.defaultMode(Pug4J.Mode.HTML)
.build();
String prettyHtml = engine.render(template, model, context);Key concepts:
- PugEngine: Immutable template factory - configure once, use many times
- RenderContext: Immutable render settings - can be reused or created per-render
- PugTemplate: Parsed template - obtained from engine, rendered via engine
PugEngine handles template caching automatically. If you request the same unmodified template twice, you'll get the same instance and avoid unnecessary parsing.
PugTemplate t1 = engine.getTemplate("index.pug");
PugTemplate t2 = engine.getTemplate("index.pug");
t1.equals(t2) // trueClear the template and expression cache:
engine.clearCache();Configure caching at build time:
PugEngine engine = PugEngine.builder()
.caching(false) // Disable for development
.maxCacheSize(500) // Limit cache size
.expressionCacheSize(1000) // Configure expression cache
.build();By default, Pug4J produces compressed HTML without unneeded whitespace. You can enable pretty printing using RenderContext:
RenderContext context = RenderContext.builder()
.prettyPrint(true)
.build();
String html = engine.render(template, model, context);Pug detects if it has to generate (X)HTML or XML code by your specified doctype.
If you are rendering partial templates that don't include a doctype, pug4j generates HTML code. You can set the defaultMode manually:
RenderContext context = RenderContext.builder()
.defaultMode(Pug4J.Mode.HTML) // <input checked>
.defaultMode(Pug4J.Mode.XHTML) // <input checked="true" />
.defaultMode(Pug4J.Mode.XML) // <input checked="true"></input>
.build();Filters allow embedding content like markdown into your pug template:
:markdown
# headline
hello **world**
will generate
<h1>headline</h1>
<p>hello <strong>world</strong></p>
pug4j comes with built-in cdata, css, and js filters. You can add custom filters when building your engine:
PugEngine engine = PugEngine.builder()
.filter("markdown", new MarkdownFilter())
.build();To implement your own filter, you have to implement the Filter Interface. If your filter doesn't use any data from the model you can inherit from the abstract CachingFilter and also get caching for free. See the neuland/jade4j-coffeescript-filter project as an example.
If you need to call custom java functions the easiest way is to create helper classes and put an instance into the model.
public class MathHelper {
public long round(double number) {
return Math.round(number);
}
}model.put("math", new MathHelper());Note: Helpers don't have their own namespace, so you have to be careful not to overwrite them with other variables.
p= math.round(1.44)
If you are using multiple templates, you might need default objects available in all renders. Use globalVariables in RenderContext:
Map<String, Object> globals = new HashMap<>();
globals.put("city", "Bremen");
globals.put("country", "Germany");
globals.put("url", new MyUrlHelper());
RenderContext context = RenderContext.builder()
.globalVariables(globals)
.build();
// These variables are now available in every render using this context
String html = engine.render(template, model, context);Since version 3.0.0, pug4j supports Java records as model objects. Records are automatically wrapped to make their components accessible in templates using property syntax, just like with Maps or POJOs.
Example:
// Define records
record Author(String name, String email) {}
record Book(String title, double price, boolean available, Author author) {}
// Create model with records
Author author = new Author("Douglas Adams", "[email protected]");
Book book = new Book("The Hitchhiker's Guide to the Galaxy", 5.70, true, author);
Map<String, Object> model = new HashMap<>();
model.put("book", book);Template usage:
div
h1= book.title
p Price: #{book.price} €
if book.available
p In stock!
p Author: #{book.author.name} (#{book.author.email})Key features:
- Automatic wrapping: Records are automatically wrapped when added to the model
- Nested records: Nested records are fully supported (e.g.,
book.author.name) - Property access: Use dot notation (
book.title) instead of method calls (book.title()) - Custom methods: Records with custom methods can call them using function syntax (
record.customMethod()) - Both expression handlers: Works with both JEXL (default) and GraalJS expression handlers
- Immutable: Records remain immutable in templates
Requirements:
- Java 17 or higher (required for record support)
By default, pug4j searches for template files in your work directory. By specifying your own FileTemplateLoader, you can alter that behavior. You can also implement the TemplateLoader interface to create your own.
TemplateLoader loader = new FileTemplateLoader("/templates/", "UTF-8");
loader.setBase("my-maintemplates/");
PugEngine engine = PugEngine.builder()
.templateLoader(loader)
.build();/indexpoints to/templates/my-maintemplates/index.pugindexpoints to/templates/index.pug
Available loaders:
FileTemplateLoader- loads from filesystemClasspathTemplateLoader- loads from classpathReaderTemplateLoader- loads from Reader instances
You can also implement the TemplateLoader interface to create your own custom loader.
The original pug implementation uses JavaScript for expression handling in if, unless, for, case commands, like this
- var book = {"price": 4.99, "title": "The Book"}
if book.price < 5.50 && !book.soldOut
p.sale special offer: #{book.title}
each author in ["artur", "stefan", "michael","christoph"]
h2= author
Pug4j uses JEXL for parsing and executing these expressions. JEXL syntax and behavior is very similar to ECMAScript/JavaScript and so closer to the original pug.js implementation. JEXL runs also much faster than GraalVM. If your template don't relies too much on Javascript-Logic and gets almost everything from the model, this is a good choice.
We are using a slightly modified JEXL version which to have better control of the exception handling. JEXL now runs in a semi-strict mode, where non existing values and properties silently evaluate to null/false where as invalid method calls lead to a PugCompilerException.
JEXL comes with the three builtin functions new, size and empty. For properties with this name the . notation does not work, but you can access them with [].
- var book = {size: 540}
book.size // does not work
book["size"] // works
You can read more about this in the JEXL documentation.
If you want to use pure JavaScript expression handling, you can use the GraalJS Expression Handler. It supports native JavaScript expressions but is significantly slower than the JEXL Expression Handler. Configure it when building your engine:
PugEngine engine = PugEngine.builder()
.expressionHandler(new GraalJsExpressionHandler())
.build();- neuland/spring-pug4j pug4j spring integration.
- vertx-web jade4j for Vert.X
PugConfigurationdeprecated: Replaced by immutablePugEngineandRenderContext- Migration required: See examples in Full API section above
- Old API still works but will be removed in 4.0.0
- Templates no longer self-render: Use
engine.render(template, model, context)instead oftemplate.render(model, context) - Simple API changes:
Pug4J.getTemplate()methods deprecated (not part of simple API)- Template-based
Pug4J.render(template, ...)methods deprecated - Use
Pug4J.render(filename, ...)for simple cases orPugEnginefor advanced use
- Java 17+ required: Minimum Java version raised from Java 8 to Java 17
- Dependency updates:
- GraalVM updated to 25.0.0 (simplified dependencies using
polyglotandjs-community) - Caffeine cache updated to 3.2.2
- Flexmark updated to 0.64.8
- GraalVM updated to 25.0.0 (simplified dependencies using
- Java records support: Records are now automatically wrapped when added to model
- Immutable builder pattern: Thread-safe configuration with builder pattern
- Better separation of concerns: Template loading, caching, and rendering are clearly separated
- Classes are renamed to pug4j.
- Default file extension is now .pug
- Compiler Level has been raised to Java 8+
- Syntax has been adapted to the most current pug version. (2.0.4)
- Filter interface changed
- Interpolations not supported in attributes and filters anymore. It now behaves the same way as in pug.js.
- Fixed a mayor scoping bug in loops. Use this version and not 1.3.0
- setBasePath has been removed from JadeConfiguration. Set folderPath on FileTemplateLoader instead.
- Scoping of variables in loops changed, so its more in line with jade. This could break your template.
- Breaking change in filter interface: if you use filters outside of the project, they need to be adapted to new interface
In Version 1.0.0 we added a lot of features of JadeJs 1.11. There are also some Breaking Changes:
- Instead of 'id = 5' you must use '- var id = 5'
- Instead of 'h1(attributes, class = "test")' you must use 'h1(class= "test")&attributes(attributes)'
- Instead of '!!! 5' you must use 'doctype html'
- Jade Syntax for Conditional Comments is not supported anymore
- Thanks to rzara for contributing to issue-108
- Artur Tomas / atomiccoder
- Stefan Kuper / planetk
- Michael Geers / naltatis
- Christoph Blömer / chbloemer
Special thanks to TJ Holowaychuk the creator of jade!
The MIT License
Copyright (C) 2011-2025 neuland Büro für Informatik, Bremen, Germany
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