JBang Cheatsheet (2023)

Here is my JBang cheatsheet which can help as a reference to code self-contained source-only Java programs with unmatched ease.

Getting started with JBang

Install JBang on Linux

curl -Ls https://sh.jbang.dev | bash -s - app setup

Run a JBang Script

jbang example.java

Create an executable JAR from a JBang script:

jbang export portable MyApp.java

Create a JBang class  from a template

jbang init --template=hello helloworld.java

List of available JBang templates

jbang template list

Run a Java class

jbang helloworld.java

How to run a Java class in a JAR file

jbang jgroups-4.2.15.Final.jar --main=org.jgroups.tests.McastReceiverTest

How to run a Java class using Maven GAV coordinates

jbang org.jgroups:jgroups:5.1.9.Final --main=org.jgroups.tests.McastReceiverTest 

How to run a Java code snippet:

echo "hello world" | jbang -c 'lines().forEach(s->println(s.substring(6)))`

Update JBang

To update JBang run the following command:

jbang version --update

Please note that if your current JDK is not aligned with the latest version of Java installed with JBang (see section JDK Configuration), the following error can occur during the update:

javax.net.ssl.SSLHandshakeException: Received fatal alert: handshake_failure


Adding dependency

//DEPS log4j:log4j:1.2.17

Adding GitHub project (JBang will download the project, build it as use it as a dependency)

//DEPS https://github.com/DiUS/java-faker

Adding Managed Dependencies (BOM)

//DEPS io.quarkus:quarkus-bom:[email protected]
//DEPS io.quarkus:quarkus-resteasy
//DEPS io.quarkus:quarkus-smallrye-openapi

Using System properties in the comments

//DEPS org.openjfx:javafx-graphics:11.0.2:${os.detected.jfxname}

Using Environment variables in the comments

//DEPS org.openjfx:javafx-graphics:11.0.2:${env.jfxname}

Repository for dependencies (maven repository + custom repository)

//REPOS mavencentral,acme=https://maven.acme.local/maven

Finally, please note that you can also pass the dependencies as command line argument:

jbang --deps org.matheclipse:matheclipse-core:2.0.0,org.matheclipse:matheclipse-io:2.0.0 test.java

Adding file resources

//FILES resource.properties
//FILES META-INF/resources/index.html=index.html

Adding a Manifest file:

//MANIFEST version=${version:unknown}

Setting Quarkus properties

//Q:CONFIG quarkus.datasource.db-kind=postgresql

Remote file expansion (JBang will download the remote file – tagged with % – and pass it as argument)

jbang CountWords.java %https://github.com/dwyl/english-words/raw/master/words.txt

Java Sources

Location of Java Sources

//SOURCES nested/*.java
//SOURCES othernested/*.java

You can also pass the sources (and resources) location from the command line:

jbang --sources src/main/java --files src/main/resources script.java

JDK configuration

Setting JDK in your code

//JAVA 11 will force use of Java 11.
//JAVA 13+ will require at least java 13. Java 13 or higher will be used.

Install a JDK

jbang jdk install 17

Install a JDK already available on your machine:

jbang jdk install 17 `sdk home java`

Uninstall a JDK

jbang jdk uninstall 14

List available JDK

jbang jdk list

Setting default JDK

jbang jdk default 12

Debugging and JDK Settings

Debugging a Java class

jbang --debug helloworld.java

Setting java and javac options

//JAVAC_OPTIONS -source 11
//JAVA_OPTIONS -Xms128m -Xmx512m


Install an app from the Catalog

jbang app install [email protected]/camel

List of available apps

jbang app list