javaup

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Let every Maven project use the right Java toolchain automatically.

javaup is a Java toolchain manager for Maven projects. It automatically detects the Java version and mvn executable each project needs, and remembers its selected settings.xml. Initialize a project once, then build it from any terminal with a single command — without worrying about using the wrong JDK, Maven executable, or settings.xml file.

Why javaup?

A single dev machine often runs Maven builds that target several different Java versions, such as Java 8, Java 17, and Java 21. Without jup, every project switch means manually editing JAVA_HOME and PATH, keeping track of which Java version and which Maven each repository needs, and occasionally dealing with projects that rely on different settings.xml files. It all gets tedious.

javaup (command: jup) takes care of this for you. It automatically detects the Java version a Maven project needs, picks a matching local JDK, and remembers the Maven executable, JDK, and optional settings.xml path that project uses. It then runs the build in a fresh child process, leaving your machine's environment variables and your current shell completely untouched — safe, convenient, and fast.

flowchart LR
  subgraph before["Before: no jup, all manual"]
    direction TB
    A["switch projects"] --> B["manually edit<br/>JAVA_HOME + PATH"]
    B --> C["remember this project's<br/>Maven + settings.xml"]
    C --> D["manually run the build"]
    D -->|"repeat this routine"| A
  end

  subgraph after["Now: with jup, fully automatic"]
    direction TB
    E["run jup run mvn<br/>from any terminal"] --> F["jup auto-loads<br/>your saved toolchain"]
    F --> G["jup auto-matches<br/>JDK + Maven + settings.xml"]
    G --> H["build in an<br/>isolated process"]
  end

  before ~~~ after

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jup complements existing Java tools instead of replacing them:

• SDKMAN! and asdf install or switch tools for a user or shell. jup can discover their JDKs, as well as JDKs exposed through environment variables and PATH.
• Maven Wrapper pins the Maven distribution for a repository. jup detects and prefers it automatically.
• Maven Toolchains lets Maven plugins select a JDK. jup also discovers <jdkHome> entries and controls the JDK that launches Maven itself.

The layer jup adds is a durable local project binding: this Maven executable + this JDK + this settings alias, launched through one stable command from any terminal.

Important

jup selects JDKs and Maven installations that are already present. It does not download or uninstall them. Apache Maven is currently the only supported build tool.

Install

macOS or Linux:

curl -fsSL https://github.com/codeboyzhou/javaup/releases/latest/download/install.sh | sh

Windows PowerShell 5.1 or later:

irm https://github.com/codeboyzhou/javaup/releases/latest/download/install.ps1 | iex

Prebuilt releases support Windows, macOS, and Linux on amd64 and arm64. See the installation guide for checksums, go install, source builds, and installer options.

Quick Start

All you need is a project with pom.xml, Maven Wrapper or mvn on PATH, and a matching full JDK installed locally:

cd /path/to/your/maven-project
jup init
jup status
jup run mvn clean package

In an interactive terminal, jup run mvn lets you select any initialized project, with frequently and recently used projects ranked first. In CI or redirected pipelines, it resolves the nearest initialized project without prompting.

What It Does

• Detects Java requirements from POM properties, compiler plugin configuration, and local parent POMs.
• Prefers Maven Wrapper and falls back to Maven from PATH.
• Finds installed JDKs through Maven, SDKMAN!, asdf, environment variables, PATH, Maven Toolchains, and common platform locations.
• Applies the selected JDK and optional Maven settings alias only to the spawned build process.
• Manages and diagnoses initialized projects globally without modifying project source files.

Contributing

Bug reports, compatibility cases, documentation improvements, and code contributions are welcome. Run the complete local verification pipeline with:

go mod download
go run build.go verify

Read CONTRIBUTING.md before submitting a pull request.

License

Licensed under the Apache License 2.0.