Cheatography
https://cheatography.com
Unleash the power of Java https://www.jbang.dev/
Simple JBang Hello.java
///usr/bin/env jbang "$0" "$@" ; exit $?
class Hello {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
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Run JBang script
$ jbang Hello.java
$ jbang --debug Hello.java
$ chmod u+x
$ ./Hello.java
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Templates
$ jbang template list
$ jbang init --template=cli helloworld.java
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ChatGPT - init script from ChatGPT
$ jbang init HelloCli.java "generate hello command with picocli library"
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You need an OPENAI_API_KEY environment variable.
Editing
$ jbang edit helloworld.java
$ jbang edit --open=code helloworld.java
$ jbang edit --open=idea helloworld.java
Assign Java version
//JAVA 8 |
Assigned version in Script |
//JAVA 11+ |
Java 11 or higher |
jbang --java 8 Hello.java |
Assigned version from CLI |
jbang jdk list --available |
List available JDKs |
If you don't assign Java version, and JBang will run the script with Java 17 by default.
java and javac Options
//JAVAC_OPTIONS -parameters
//JAVA_OPTIONS -Dnick=xxx
//JAVA_OPTIONS -Dserver.port=8081 -D spring.application.name=app1
//PREVIEW
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Java preview
///usr/bin/env jbang "$0" "$@" ; exit $?
//PREVIEW
//JAVA 21
void main() {
System.out.println("Hello World");
}
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Multiple Java source files
//SOURCES UserService.java
//SOURCES impl/UserServiceImpl.java
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Multi resource files - properties/xml etc
//FILES application.properties
//FILES META-INF/resources/index.html=index.html
//FILES META-INF/resources/jquery.js=https://code.jquery.com/jquery-3.6.0.min.js
//FILES templates/HelloWorld.txt.mtl=templates/HelloWorld.txt.mtl
Resource import format: //FILES <mountpoint>[=<sourcefile>]
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Polyglot - Kotlin
///usr/bin/env jbang "$0" "$@" ; exit $?
//KOTLIN 1.8.21
//DEPS org.jetbrains.kotlin:kotlin-bom:1.8.21@pom
//DEPS org.jetbrains.kotlin:kotlin-stdlib
public fun main() {
println("Hello World");
}
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Polyglot - Groovy
///usr/bin/env jbang "$0" "$@" ; exit $?
//GROOVY 4.0.12
println("Hello World");
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Polyglot - JShell
///usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS net.datafaker:datafaker:1.9.0
import net.datafaker.Faker;
Faker faker = new Faker();
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$ jbang demo.jsh
$ jbang --interactive demo.jsh
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Dependencies
//DEPS systems.manifold:manifold-all:2023.1.10
//DEPS org.projectlombok:lombok:1.18.28
//DEPS org.slf4j:slf4j-simple:2.0.7
//DEPS libs/local.jar
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Managed dependencies by BOM - Spring Boot
//DEPS org.springframework.boot:spring-boot-dependencies:2.7.11@pom
//DEPS org.springframework.boot:spring-boot-starter
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Managed dependencies by BOM - Quarkus
//DEPS io.quarkus:quarkus-bom:2.9.2.Final@pom
//DEPS io.quarkus:quarkus-resteasy
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Catalogs - jbang-catalog.json
{
"aliases": {
"hello": {
"script-ref": "hello.java",
"description": "Script that says hello back for each argument"
}
}
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Catalogs - local jbang-catalogs.json
1. jbang-catalog.json in current directory |
2. jbang-catalog.json in parent directory util the root diretory |
3. $HOME/.jbang/jbang-catalog.json |
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Catalogs - implicit catalog from GitHub
jbang hello@acme |
hello alias in acme/jbang-catalog/jbang-catalog.json |
jbang hello@acme/mycatalog |
hello alias in acme/mycatalog/jbang-catalog.json |
jbang hello@acme/mycatalog/dev |
hello alias in acme/mycatalog/jbang-catalog.json in dev branch |
jbang hello@acme~experimental |
hello alias in acme/jbang-catalog/experimental/jbang-catalog.json |
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Catalogs - management
$ jbang catalog add --name acme acme
$ jbang catalog add --name mycatalog acme/mycatalog
$ jbang catalog list
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Tips
jbang --fresh |
Use none-cached resources |
jbang info tools Hello.java |
Prints a json description of JBang script |
Apps - setup jbang to put scripts into your PATH
$ jbang app install <scriptRef>
$ $ jbang app install --name app1 <scriptRef>
$ jbang app list
$ jbang app uninstall <name>
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build.java
///usr/bin/env jbang "$0" "$@" ; exit $?
//JAVA 17
//DEPS info.picocli:picocli:4.7.3
//SOURCES src
//FILES resources
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JBang export - generate jar or native binary
jbang export fatjar |
Exports an executable fat jar with all dependencies |
jbang export portable |
Exports jar together with dependencies in pom.xml |
jbang export native |
Exports native executable |
jbang export mavenrepo |
Exports directory that can be used to publish as a maven repository |
jbang export jlink |
Export app with Java runtime embedded |
JBang with ChatGPT
export OPENAI_API_KEY=sk-xxxxxxx-x-xxxxxx
jbang init gh.java "connect to github an fetch all repositories under jbangdev and collect how many stars they have"
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