java-manager

A comprehensive Rust library for discovering, managing, and interacting with Java installations.

Features

• Cross‑platform – Works on Windows, macOS, and Linux.
• Java discovery – Find Java via PATH (quick_search), Everything SDK on Windows (deep_search, requires everything feature), or multi‑strategy full scan (full_search):
  • Windows: Registry (HKLM + HKCU, including Azul, BellSoft, Temurin, Corretto, GraalVM), keyword BFS, Microsoft Store, where command, Chocolatey, Scoop, JetBrains bundled JDK.
  • Linux: walkdir over /usr/lib/jvm, /usr/java, /opt, /usr/local, plus SDKMAN, JBang, asdf‑vm, JetBrains bundled JDK, Minecraft runtime.
  • macOS: /Library/Java/JavaVirtualMachines, /usr/libexec/java_home, plus SDKMAN, JBang, asdf‑vm, Homebrew, JetBrains bundled JDK, Minecraft runtime.
  • All platforms: $JAVA_HOME is always checked first.
• Structured metadata – JavaInfo provides name, version, vendor, architecture, JAVA_HOME, parsed JavaVersion, and JDK capabilities.
• Version matching – best_match() and filter_by_version() let you pick the right Java by version requirement ("17", "17.0", "17.0.2").
• Execution control – Run JARs or main classes with JavaRunner: classpath, module path, --add-opens/--add-exports, system properties, memory limits, environment variables, working directory, process timeout, I/O redirection with append mode.
• TTL caching – JavaCache avoids redundant full‑disk scans (default 300 s TTL).
• Parallel search – Optional parallel feature enables rayon‑powered concurrent JavaInfo resolution.
• Download – Optional download feature for async, resumable, parallel‑chunked JDK downloads with automatic extraction (ZIP / tar.gz).
• Debug logging – Built‑in log crate integration.
• Nested JRE dedup – Automatically removes bundled JREs that are sub‑directories of a parent JDK.

Installation

[dependencies]
java-manager = "0.4"

Or:

cargo add java-manager

Optional features

Usage

Locate Java installations

use java_manager::{quick_search, deep_search, full_search, java_home};

// Quick search: look for 'java' in every directory in PATH
let javas = quick_search()?;
for java in javas {
    println!("Found Java at {} (version {})", java.path.display(), java.version);
}

// Deep search: Everything SDK (Windows, falls back to full_search) or walkdir (Linux/macOS)
let all_javas = deep_search()?;

// Full search: registry + BFS + MS Store + where + package managers + IDE paths
let all_javas = full_search()?;

// Check JAVA_HOME environment variable
if let Some(java) = java_home() {
    println!("JAVA_HOME points to Java version {}", java.version);
}

Filter by version requirement

use java_manager::{quick_search, best_match, filter_by_version};

let javas = quick_search()?;

// Best match for Java 17 (highest patch version)
if let Some(java17) = best_match(javas.clone(), "17") {
    println!("Best Java 17: {} (version {})", java17.path.display(), java17.version);
}

// All Java 11 installations
let java11_installs = filter_by_version(javas, "11");

Cached search

use java_manager::{JavaCache, full_search};
use std::time::Duration;

let mut cache = JavaCache::new(Duration::from_secs(300));

// First call runs the search, subsequent calls are cached
let javas = cache.get_or_refresh(|| full_search())?;

// Force a refresh
let javas = cache.force_refresh(|| full_search())?;

Parallel search (requires parallel feature)

use java_manager::parallel_full_search;

let javas = parallel_full_search()?;

Execute a Java program

use java_manager::{JavaRunner, JavaRedirect, java_home};

let java = java_home().expect("JAVA_HOME not set");

// Run a JAR file with memory limits and I/O redirection
JavaRunner::new()
    .java(java.clone())
    .jar("myapp.jar")
    .min_memory(256 * 1024 * 1024)   // 256 MB
    .max_memory(1024 * 1024 * 1024)  // 1 GB
    .arg("--server")
    .redirect(JavaRedirect::new().output("out.log").error("err.log"))
    .execute()?;

// Or run a main class
JavaRunner::new()
    .java(java)
    .main_class("com.example.Main")
    .arg("arg1")
    .arg("arg2")
    .execute()?;

Advanced JavaRunner

use java_manager::{JavaRunner, java_home};
use std::time::Duration;

let java = java_home().expect("JAVA_HOME not set");

JavaRunner::new()
    .java(java)
    .jar("app.jar")
    .classpath(&["lib/*", "config/"])
    .add_opens("java.base", "java.lang", "ALL-UNNAMED")
    .add_exports("java.base", "com.sun.internal", "ALL-UNNAMED")
    .system_property("myapp.config", "prod")
    .env("MY_VAR", "value")
    .working_dir("/opt/myapp")
    .timeout(Duration::from_secs(30))
    .redirect(
        JavaRedirect::new()
            .output("app.log")
            .append_output()
            .error("app.err")
            .append_error()
    )
    .execute()?;

JDK detection and capabilities

use java_manager::JavaInfo;

let info = JavaInfo::new("/usr/lib/jvm/java-17-openjdk/bin/java".into())?;

// Check if this is a full JDK (has javac)
if info.is_jdk() {
    println!("Full JDK detected");
}

// List available JDK tools
let tools = info.capabilities();
println!("Available tools: {:?}", tools);
// e.g. ["javac", "javadoc", "jar", "jlink", "jshell", "jcmd"]

Metadata from a specific Java path

use java_manager::JavaInfo;

let info = JavaInfo::new("/usr/lib/jvm/java-11-openjdk/bin/java".into())?;
println!("Name: {}", info.name);
println!("Version: {}", info.version);
println!("Parsed version: {}", info.parsed_version.unwrap());
println!("Vendor: {}", info.vendor);
println!("Architecture: {}", info.architecture);
println!("JAVA_HOME: {}", info.java_home.display());

API Overview

JavaRunner builder methods

JavaRedirect methods

Version requirement syntax

Search Strategy Details

full_search() attempts multiple discovery strategies on each platform:

Nested JRE deduplication: When both a JDK and its bundled JRE are discovered (e.g. jdk-xxx/jre/bin/java.exe), only the JDK-level installation is kept. Standalone JREs are unaffected.

deep_search() fallback: On Windows, when the everything feature is enabled and the Everything SDK is not available (service not running / not installed), deep_search() automatically falls back to full_search(). Without the everything feature, deep_search() always delegates to full_search().

Debug Logging

Enable logging to see what the library is doing behind the scenes:

RUST_LOG=debug cargo run

This will output scan paths, registry keys checked, stale entries skipped, and version parsing results.

License

This project is licensed under the MIT License. See the LICENSE file for details.