Developer Documentation Overview

Overview

This section explains how to extend Fess. It provides information on plugin development, custom connector creation, theme customization, and other ways to extend Fess.

Target Audience

  • Developers who want to create custom features for Fess

  • Developers who want to create plugins

  • Developers who want to understand the Fess source code

Prerequisites

  • Basic knowledge of Java 21

  • Basics of Maven (build system)

  • Experience with web application development

Development Environment

Setup

  1. Get the source code:

git clone https://github.com/codelibs/fess.git
cd fess

  1. Build:

mvn package -DskipTests

  1. Start the development server:

./bin/fess

Architecture Overview

Fess consists of the following major components:

Component Structure

Component Description
Web Layer MVC implementation using LastaFlute framework
Service Layer Business logic
Data Access Layer OpenSearch integration using DBFlute
Crawler Content collection using fess-crawler library
Search Engine Full-text search using OpenSearch

Major Frameworks

  • LastaFlute: Web framework (actions, forms, validation)

  • DBFlute: Data access framework (OpenSearch integration)

  • Lasta Di: Dependency injection container

Directory Structure

fess/
├── src/main/java/org/codelibs/fess/
│   ├── app/
│   │   ├── web/         # Controllers (Action)
│   │   ├── service/     # Services
│   │   └── pager/       # Pagination
│   ├── api/             # REST API
│   ├── helper/          # Helper classes
│   ├── crawler/         # Crawler related
│   ├── opensearch/      # OpenSearch integration (DBFlute generated)
│   ├── llm/             # LLM integration
│   └── ds/              # DataStore connectors
├── src/main/resources/
│   ├── fess_config.properties  # Configuration
│   └── fess_*.xml              # DI configuration
└── src/main/webapp/
    └── WEB-INF/view/    # JSP templates

Extension Points

Fess provides the following extension points:

Plugins

You can add features using plugins.

  • DataStore Plugin: Crawl from new data sources

  • Script Engine Plugin: Support for new scripting languages

  • Web App Plugin: Extend the web interface

  • Ingest Plugin: Process data during indexing

Details: Plugin Architecture

Themes

You can customize the design of the search screen.

Details: Theme Development Guide

Configuration

Many behaviors can be customized via fess_config.properties.

Details: Introduction

Plugin Development

For details on plugin development, see the following:

Theme Development

Best Practices

Coding Standards

  • Follow the existing Fess code style

  • Format code with mvn formatter:format

  • Add license headers with mvn license:format

Testing

  • Write unit tests (*Test.java)

  • Integration tests use *Tests.java

Logging

  • Use Log4j2

  • Use logger.debug() / logger.info() / logger.warn() / logger.error()

  • Do not log sensitive information

Resources