Throwable cause1 = exception.getCause();
        assertNotNull(cause1);
        assertTrue(cause1 instanceof IOException);
        assertEquals("Level 1 error", cause1.getMessage());

        Throwable cause2 = cause1.getCause();
        assertNotNull(cause2);
        assertTrue(cause2 instanceof IllegalStateException);
        assertEquals("Level 2 error", cause2.getMessage());

- Use `OptionalEntity<T>` for nullable returns
- Plain classes (no extends/implements)

### Helper
- Stateless utility classes
- Access via `ComponentUtil.getXyzHelper()`
- Named with "Helper" suffix

### DBFlute Generated Code
```
opensearch/{index}/
├── bsentity/, bsbhv/    # Base classes (DO NOT EDIT)
├── exentity/, exbhv/    # Extended classes (customize here)

# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

curl4j is a simple cURL-like Java HTTP client library providing a fluent API for building HTTP requests. It's designed to be minimal with only Apache Commons IO as a dependency.

## Directory Structure

```
curl4j/
├── src/
│   ├── main/java/org/codelibs/curl/

mvn license:format                    # Apply license headers
mvn verify                            # Generate coverage report
```

## Code Conventions

### Class Structure

- **Utility classes**: `abstract` class + `protected` constructor
- **Constants classes**: Same pattern

### Argument Validation

Use `AssertionUtil` at method entry:
- `AssertionUtil.assertArgumentNotNull("argName", value)`

# CLAUDE.md - Fess Crawler Development Guide

Quick reference for AI assistants working on the Fess Crawler project.

## Project Overview

**Fess Crawler** is a Java-based web crawling framework for enterprise content extraction.

### Essential Info

- **Language**: Java 21+
- **Build**: Maven 3.x
- **License**: Apache 2.0
- **DI**: LastaFlute DI
- **Repo**: https://github.com/codelibs/fess-crawler

### Tech Stack

# CLAUDE.md - Fess Suggest Project Guide

> AI assistant guidance for the Fess Suggest project - a Java library providing intelligent search suggestions built on OpenSearch.

## Project Overview

**Fess Suggest** delivers auto-completion, search suggestions, and popular word analytics with multi-language support.

**Technology Stack:**
- Java 21+, Maven
- OpenSearch (provided dependency)
- Apache Lucene (query parsing, text analysis)

        assertTrue(exception.aborted());

        // Verify the cause chain
        Throwable cause1 = exception.getCause();
        assertTrue(cause1 instanceof RuntimeException);

        Throwable cause2 = cause1.getCause();
        assertTrue(cause2 instanceof AssertionError);

        Throwable cause3 = cause2.getCause();
        assertTrue(cause3 instanceof NullPointerException);
    }

    @Test

```

entonces es un "callable".

## Clases como dependencias { #classes-as-dependencies_1 }

Puedes notar que para crear una instance de una clase en Python, utilizas esa misma sintaxis.

Por ejemplo:

```Python
class Cat:
    def __init__(self, name: str):
        self.name = name


fluffy = Cat(name="Mr Fluffy")
```

En este caso, `fluffy` es una instance de la clase `Cat`.

Nesse caso,  `fluffy` é uma instância da classe `Cat`.

E para criar `fluffy`, você está "chamando" `Cat`.

Então, uma classe Python também é "chamável".

Então, no **FastAPI**, você pode utilizar uma classe Python como uma dependência.

O que o FastAPI realmente verifica, é se a dependência é algo chamável (função, classe, ou outra coisa) e os parâmetros que foram definidos.

Et pour créer `fluffy`, vous « appelez » `Cat`.

Donc, une classe Python est aussi un « callable ».

Ainsi, avec **FastAPI**, vous pouvez utiliser une classe Python comme dépendance.

Ce que **FastAPI** vérifie réellement, c'est qu'il s'agit d'un « callable » (fonction, classe ou autre) et des paramètres qui y sont définis.