Velocity Template Previewer

Desktop application for previewing and rendering Apache Velocity templates with real-time syntax highlighting and validation. Perfect for developers working with Atlassian products (Jira, Confluence), ScriptRunner, email templates, and web applications.

What is This?

Apache Velocity is a Java-based template engine commonly used in:

• Atlassian Products: Jira email templates, Confluence macros, ScriptRunner scripts
• Email Systems: Dynamic email generation
• Web Applications: Server-side templating
• Code Generation: Template-based code scaffolding

This tool lets you preview and test your Velocity templates instantly without deploying to production.

Features

• Real-time Preview: See changes as you type
• Syntax Highlighting: Color-coded templates and JSON data
• Validation: Catch errors before deployment
• Background Rendering: Smooth performance with large templates
• Auto-save: Never lose your work (saves every 30 seconds)
• Export: Generate static HTML from your templates
• Dark Mode: Easy on the eyes
• Recent Files: Quick access to your projects

Installation

Requirements: Python 3.9+ (Windows, macOS, Linux)

git clone https://github.com/star7js/velocity-previewer.git
cd velocity-previewer
pip install -e .
velocity-previewer

Quick Start

1. Open a template: File > Open or Ctrl+O
2. Add your data: Switch to Data tab, paste JSON
3. Render: Press F5
4. Export (optional): File > Export to HTML

Try the included examples/example-template.vm with examples/example-data.json to see it in action.

Use Cases

Atlassian/ScriptRunner Development

Test Jira email notifications, Confluence macros, or ScriptRunner templates locally before deploying:

#if($issue.priority.name == "Critical")
  <span style="color: red;">$issue.key - $issue.summary</span>
#end

Email Template Design

Preview dynamic email templates with test data:

Hello $customer.name,

Your order #$order.id has shipped!
#foreach($item in $order.items)
  - $item.name (Qty: $item.quantity)
#end

Dynamic Reports

Generate reports from JSON data without manual formatting.

Keyboard Shortcuts

Action	Shortcut
Render Template	F5
Open Template	Ctrl+O
Save Template	Ctrl+S
Validate Template	Ctrl+Shift+V
Validate Data	Ctrl+Shift+D

Supported Velocity Syntax

• Variables: $variable, ${variable}
• Directives: #if, #foreach, #set, #macro
• Comments: ## (single line), #* ... *# (multi-line)
• Properties: $object.property, $array[0]
• Methods: $string.substring(0, 5)

Full Apache Velocity specification supported via Airspeed engine.

Platform Support

• ✅ Windows 10/11
• ✅ macOS 10.15+
• ✅ Linux (Ubuntu, Fedora, Arch)

Development

# Install dependencies
pip install -e .

# Run tests
python tests/test_functionality.py

# Project structure
├── src/velocity_previewer/    # Main package
│   ├── main.py                # Application UI and logic
│   ├── utils.py               # Template processing
│   └── syntax_highlighters.py # Syntax highlighting
├── examples/                  # Example templates and data
├── tests/                     # Test files
└── pyproject.toml            # Project configuration

Settings (window size, recent files) are saved to:

• Windows: %APPDATA%/VelocityPreviewer
• macOS: ~/Library/Application Support/VelocityPreviewer
• Linux: ~/.config/VelocityPreviewer

Troubleshooting

Issue	Solution
Template won't render	Use Tools > Validate Template (Ctrl+Shift+V) to see errors
JSON parse errors	Use Tools > Validate Data (Ctrl+Shift+D) to check format
Slow performance	Large templates render in background automatically
App won't start	Ensure PyQt5 is installed: pip install PyQt5

Roadmap

• Live preview mode (render on every keystroke)
• Multiple data sets for testing
• Template snippet library
• Velocity macro autocomplete

License

MIT License

Built With

• PyQt5 - Cross-platform UI framework
• Airspeed - Python implementation of Apache Velocity