Openjar indexer

Maven Indexer

Use openjar-cli to search and inspect Java classes, artifacts, and resources from your local Maven/Gradle cache.

When to activate

Use this skill when:

• You see an import (e.g. com.company.util.Helper) but cannot find the definition in the workspace — it likely comes from a compiled internal library
• You need to read the actual implementation of an internal or non-well-known library ("Don't guess what the internal library does — read the code")
• You need to find which artifact contains a given class
• You need method signatures, Javadocs, or full source code of a dependency class
• You need to find implementations of an interface or subclasses of a base class (e.g. SPI implementations)
• You need to locate proto files or other resources embedded in JARs

Skip when:

• The class is from the standard Java library (java.util, java.io, etc.) or a well-known public library the AI already knows well
• The source is already present in the current workspace

Check index first

If the index might be empty or stale, build it first:

# Quick scan — one best version per artifact (fast, recommended)
openjar-cli refresh

# Full scan — all versions of all artifacts
openjar-cli refresh --full

Commands

class — Find which artifact contains a class

Essential when you see an import but cannot find the definition. Do not assume the source is local just because the code compiles.

openjar-cli class <className>
# Examples:
openjar-cli class StringUtils
openjar-cli class com.company.util.Helper
openjar-cli class JsonToXml          # keyword search also works

detail — Read the actual implementation

Use instead of guessing. Prefers source JARs, falls back to decompilation.

# Method signatures (default)
openjar-cli detail <className>

# Javadocs + method signatures
openjar-cli detail <className> --type docs

# Full source code
openjar-cli detail <className> --type source

# From a specific artifact version
openjar-cli detail <className> --coordinate groupId:artifactId:version

artifact — Find artifacts by coordinate or keyword

openjar-cli artifact <query>
# Examples:
openjar-cli artifact guava
openjar-cli artifact com.google.guava

impl — Find SPI implementations and subclasses

Particularly useful for finding implementations of SPIs or base classes within internal company libraries.

openjar-cli impl <className>
# Examples:
openjar-cli impl java.util.List
openjar-cli impl com.example.spi.Handler

resource — Find proto files and other JAR resources

openjar-cli resource <pattern>
# Examples:
openjar-cli resource .proto
openjar-cli resource log4j.xml

Output

All commands support --json for structured output:

openjar-cli class ImmutableList --json
openjar-cli detail com.google.common.collect.ImmutableList --json

If openjar-cli is not found, install it: npm install -g openjar-cli