Apache Fesod (Incubating) AI Agent Instructions

This file provides guidance for AI coding agents working with the Apache Fesod (Incubating) codebase.

Project Overview

Apache Fesod (Incubating) is a Java library for processing spreadsheets (XLS/XLSX/CSV) without OOM, derived from Alibaba EasyExcel. It uses Apache POI under the hood with streaming SAX-based reading. The project is an Apache incubator project and must follow ASF conventions.

• Language: Java 8+ (source/target = 1.8; CI builds on JDK 8, 11, 17, 21, 25 — JDK 17+ is recommended for local development)
• Build: Maven 3.6.3 via ./mvnw wrapper (project docs require 3.9+, but wrapper currently pins 3.6.3; both work)
• CI matrix: JDK 8, 11, 17, 21, 25

Build & Test Commands

# Build (runs tests by default, per Maven/Apache convention)
./mvnw clean install

# Fast build without running tests
./mvnw clean install -DskipTests

# Run tests for the library modules only
./mvnw clean package -pl fesod-common,fesod-shaded,fesod-sheet

# Format check / auto-format
./mvnw spotless:check
./mvnw spotless:apply

# Run tests by tag
./mvnw test -Dtest.groups=unit          # fast unit tests only
./mvnw test -Dtest.excludedGroups=fuzz  # exclude slow fuzz tests

# Full install with javadoc (CI validation)
./mvnw install -B -V
./mvnw javadoc:javadoc

Code Style & Conventions

• Formatter: Palantir Java Format (enforced by Spotless); Checkstyle checks import restrictions during Maven's validate phase
• Imports: Static imports first, then regular imports; no unused imports (enforced by Spotless importOrder with \#| separator)
• Import restrictions: Checkstyle allows named static imports from JUnit Assertions/Assumptions, Mockito Mockito/ArgumentMatchers, and AssertJ Assertions through AvoidStaticImport.excludes. These libraries have Maven test scope and are unavailable to production compilation. Other static imports and all wildcard imports remain forbidden by Checkstyle.
• Indent: 4 spaces
• License header: ASF Apache 2.0 header required on all .java, .xml, .yml, .toml files. Header template at tools/spotless/license-header.txt; enforced by the Hawkeye workflow (.github/workflows/license-check.yml), not Spotless
• Lombok: Allowed; config in lombok.config (toString.callSuper = CALL, equalsAndHashCode.callSuper = CALL)
• Commits: English, format type: description (types: fix, feat, refactor, test, docs, chore, style, dependency)

Module Structure

(root)                 # Root POM (artifactId: fesod-parent), dependency & plugin management
├── fesod-common/      # Zero-dependency utilities (org.apache.fesod.common.util)
├── fesod-shaded/      # Relocated Spring ASM/cglib (org.apache.fesod.shaded)
├── fesod-bom/         # BOM for downstream consumers
└── fesod-sheet/       # Core library: read/write XLS/XLSX/CSV via POI
    ├── src/main/java/org/apache/fesod/sheet/
    │   ├── FesodSheet.java    # Main entry: FesodSheet.read() / FesodSheet.write()
    │   ├── analysis/          # Read pipeline (v03=XLS BIFF, v07=XLSX SAX, csv)
    │   ├── write/             # Write pipeline (builder, executor, handler chains)
    │   ├── metadata/          # Data models, builders, csv/ property/
    │   ├── converters/        # Type conversion framework (by Java type)
    │   └── util/              # DateUtils, NumberUtils, WorkBookUtil, etc.
    └── src/test/java/org/apache/fesod/sheet/
        └── testkit/           # Test infrastructure (NOT a separate module)
            ├── Tags.java      # @Tag constants: unit, round-trip, read, write, format, fuzz
            ├── base/          # AbstractExcelTest (round-trip base)
            ├── assertions/    # ExcelAssertions fluent API
            └── builders/      # TestDataBuilder

Testing Conventions

• JUnit 5 with PER_CLASS lifecycle and ReplaceUnderscores display name generator (configured globally in fesod-sheet/src/test/resources/junit-platform.properties, not via per-class annotations)
• Tags (use @Tag(Tags.XXX)):
  • unit — pure logic, no file I/O
  • round-trip — write-then-read via AbstractExcelTest
  • read / write — single-direction tests
  • format — CSV/charset/date format tests
  • fuzz — Jazzer property-based (slow, excluded in PR CI)
• Real-file tests: Prefer AbstractExcelTest.createTempFile() + ExcelAssertions for integration tests
• Test data: Use TestDataBuilder.simpleData(n) or model classes in testkit/models/

CI Checks (must pass before merge)

1. spotless:check — format
2. License header (hawkeye)
3. Multi-JDK test matrix (8/11/17/21/25)
4. mvn install + mvn javadoc:javadoc
5. CodeQL security scan