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pug4j - a pug implementation written in Java

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.

With the addition of a new GraalJsExpressionHandler your code can be more compatible to the js version than before.

Contents

Example

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>

Syntax

See also the original https://github.com/pugjs/pug#syntax.

Usage

via Maven

Just add following dependency definitions to your pom.xml.

<dependency>
  <groupId>de.neuland-bfi</groupId>
  <artifactId>pug4j</artifactId>
  <version>2.2.0</version>
</dependency>

Build it yourself

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.

<a name="simple-api"></a>

Simple static API

Parsing template and generating template in one step.

String html = Pug4J.render("./index.pug", model);

If you use this in production you would probably do the template parsing only once per template and call the render method with different models.

PugTemplate template = Pug4J.getTemplate("./index.pug");
String html = Pug4J.render(template, model);

Streaming output using a java.io.Writer

Pug4J.render(template, model, writer);

<a name="api"></a>

Full API

If you need more control you can instantiate a PugConfiguration object.

PugConfiguration config = new PugConfiguration();

PugTemplate template = config.getTemplate("index");

Map<String, Object> model = new HashMap<String, Object>();
model.put("company", "neuland");

config.renderTemplate(template, model);

<a name="api-caching"></a>

Caching

The PugConfiguration handles template caching for you. If you request the same unmodified template twice you'll get the same instance and avoid unnecessary parsing.

PugTemplate t1 = config.getTemplate("index.pug");
PugTemplate t2 = config.getTemplate("index.pug");
t1.equals(t2) // true

You can clear the template and expression cache by calling the following:

config.clearCache();

For development mode, you can also disable caching completely:

config.setCaching(false);

<a name="api-output"></a>

Output Formatting

By default, Pug4J produces compressed HTML without unneeded whitespace. You can change this behaviour by enabling PrettyPrint:

config.setPrettyPrint(true);

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 also set the mode manually:

config.setMode(Pug4J.Mode.HTML);   // <input checked>
config.setMode(Pug4J.Mode.XHTML);  // <input checked="true" />
config.setMode(Pug4J.Mode.XML);    // <input checked="true"></input>

<a name="api-filters"></a>

Filters

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 a plain and cdata filter. plain takes your input to pass it directly through, cdata wraps your content in <![CDATA[...]]>. You can add your custom filters to your configuration.

config.setFilter("markdown", new MarkdownFilter());

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.

<a name="api-helpers"></a>

Helpers

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)

<a name="api-model-defaults"></a>

Model Defaults

If you are using multiple templates you might have the need for a set of default objects that are available in all templates.

Map<String, Object> defaults = new HashMap<String, Object>();
defaults.put("city", "Bremen");
defaults.put("country", "Germany");
defaults.put("url", new MyUrlHelper());
config.setSharedVariables(defaults);

<a name="api-template-loader"></a>

Template Loader

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");
config.setTemplateLoader(loader);

<a name="expressions"></a>

Expressions

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

Jexl Expressionhandler (default)

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. <a name="reserved-words"></a>

Reserved Words

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.

<a name="graalvm"></a>

GraalVM Expressionhandler (NEW! since 2.0.0)

If you want to use pure javascript expression handling, you can try out the new GraalJS Expression Handler. It supports native javascript expressions but is slower than the Jexl Expression Handler. You can configure it like this:

PugConfiguration config = new PugConfiguration();

config.setExpressionHandler(new GraalJsExpressionHandler())

<a name="framework-integrations"></a>

Framework Integrations

<a name="breaking-changes-2"></a>

Breaking Changes in 2.0.0

<a name="breaking-changes-1"></a>

Breaking Changes in 1.3.1

Breaking Changes in 1.3.0

Breaking Changes in 1.2.0

Breaking Changes in 1.0.0

In Version 1.0.0 we added a lot of features of JadeJs 1.11. There are also some Breaking Changes:

<a name="authors"></a>

Authors

Special thanks to TJ Holowaychuk the creator of jade!

<a name="license"></a>

License

The MIT License

Copyright (C) 2011-2024 neuland Büro für Informatik, Bremen, Germany

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.