jte: A Java repository from DevAlves1993

jte (Java Template Engine) is a secure and lightweight template engine for Java and Kotlin. jte is designed to introduce as few new keywords as possible and builds upon existing language features, so that it is very easy to reason about what a template does. The IntelliJ plugin offers full completion and refactoring support for Java parts as well as for jte keywords.

🚀 jte 3 is here! Check out the release notes for exciting new features, improved performance, and streamlined dependencies.

Features

Intuitive and easy syntax, you'll rarely need to check the documentation
Write plain Java or Kotlin for expressions, you don't need to learn yet another expression language
Context-sensitive HTML escaping at compile time
IntelliJ plugin with completion and refactoring support
Hot reloading of templates during development
Blazing fast execution (see benchmarks)

TLDR

jte gives you the same productive, type safe experience you're used to from writing Java or Kotlin. This is IntelliJ with the jte plugin installed:

5 minutes example

Here is a small jte template example.jte:

@import org.example.Page

@param Page page

<head>
    @if(page.getDescription() != null)
        <meta name="description" content="${page.getDescription()}">
    @endif
    <title>${page.getTitle()}</title>
</head>
<body>
    <h1>${page.getTitle()}</h1>
    <p>Welcome to my example page!</p>
</body>

So what is going on here?

@import directly translates to Java imports, in this case so that org.example.Page is known to the template.
@param Page page is the parameter that needs to be passed to this template.
@if/@endif is an if-block. The stuff inside the parentheses (page.getDescription() != null) is plain Java code.
${} writes to the underlying template output, as known from various other template engines.

To render this template, an instance of TemplateEngine is required. Typically you create it once per application (it is safe to share the engine between threads):

CodeResolver codeResolver = new DirectoryCodeResolver(Path.of("jte")); // This is the directory where your .jte files are located.
TemplateEngine templateEngine = TemplateEngine.create(codeResolver, ContentType.Html); // Two choices: Plain or Html

The content type passed to the engine determines how user output will be escaped. If you render HTML files, Html is highly recommended. This enables the engine to analyze HTML templates at compile time and perform context sensitive output escaping of user data, to prevent you from XSS attacks.

With the TemplateEngine ready, templates are rendered like this:

TemplateOutput output = new StringOutput();
templateEngine.render("example.jte", page, output);
System.out.println(output);

Besides StringOutput, there are several other TemplateOutput implementations you can use, or create your own if required.

If you had more than one page like example.jte, you would have to duplicate a lot of shared template code. Let's extract the shared code into another template, so that it can be reused.

Let's move stuff from our example page to layout.jte:

@import org.example.Page
@import gg.jte.Content

@param Page page
@param Content content

<head>
    @if(page.getDescription() != null)
        <meta name="description" content="${page.getDescription()}">
    @endif
    <title>${page.getTitle()}</title>
</head>
<body>
    <h1>${page.getTitle()}</h1>
    ${content}
</body>

The @param Content content is a content block that can be provided by callers of the template. ${content} renders this content block. Let's refactor example.jte to use the new template:

@import org.example.Page

@param Page page

@template.layout(page = page, content = @`
    <p>Welcome to my example page!</p>
`)

The shorthand to create content blocks within jte templates is an @ followed by two backticks. For advanced stuff, you can even create Java methods that return custom Content implementation and call it from your template code!

Check out the syntax documentation, for a more comprehensive introduction.

Performance

By design, jte provides very fast output. This is a fork of mbosecke/template-benchmark with jte included, running on AMD Ryzen 5950x (single thread):

High concurrency

This is the same benchmark as above, but the amount of threads was set to @Threads(16), to fully utilize all cores. jte has pretty much zero serialization bottlenecks and runs very concurrent on servers with a lot of CPU cores:

Getting started

jte is available on Maven Central:

Maven

<dependency>
    <groupId>gg.jte</groupId>
    <artifactId>jte</artifactId>
    <version>3.0.0</version>
</dependency>

Gradle

implementation group: 'gg.jte', name: 'jte', version: '3.0.0'

No further dependencies required! Check out the syntax documentation and have fun with jte.

DevAlves1993/jte