Configuration

Avoid repeating flags by creating a jbundle.toml in your project root.

Configuration File

# jbundle.toml

java_version = 21
target = "linux-x64"
jvm_args = ["-Xmx512m", "-XX:+UseZGC"]
profile = "cli"
appcds = true
crac = false

All fields are optional.

Options

Field	Type	Default	Description
java_version	integer	21	JDK version to bundle
target	string	current platform	Target platform (linux-x64, macos-aarch64, etc.)
jvm_args	array	[]	JVM arguments passed at runtime
profile	string	"server"	JVM profile ("cli" or "server")
appcds	boolean	true	Enable AppCDS for faster startup
crac	boolean	false	Enable CRaC checkpoint (Linux only)

Precedence

Configuration values are resolved in this order (highest to lowest):

1. CLI flags — --java-version 17 overrides everything

2. jbundle.toml — Project-level defaults

3. Internal defaults — Built-in values

Examples

CLI Tool

Optimized for fast startup:

# jbundle.toml
java_version = 21
profile = "cli"
jvm_args = ["-Xmx256m"]

Microservice

Standard server configuration:

# jbundle.toml
java_version = 21
profile = "server"
jvm_args = ["-Xmx1g", "-XX:+UseZGC"]

Cross-Platform Build

Targeting Linux from macOS:

# jbundle.toml
java_version = 21
target = "linux-x64"

Maximum Performance (Linux)

With CRaC for instant startup:

# jbundle.toml
java_version = 21
profile = "cli"
crac = true

Environment Variables

For debugging, set RUST_LOG to control jbundle's logging:

# Show debug output
RUST_LOG=debug jbundle build --input . --output ./dist/app

# Show only warnings
RUST_LOG=warn jbundle build --input . --output ./dist/app