Scripting with JBang instead of Python §

development  

I recently needed to write some scripts to automate some updates to Microservices.IO. I normally write scripts in Python (or perhaps bash, if they simple) since it’s easy to use and has lots of handy libraries. But this time I decided to try JBang, which is a tool that let’s you write scripts in Java.

Installing JBang §

First, I installed JBang using SDKMAN!:

$ sdk install jbang

Creating a JBang script §

Second, I created the script:

$ jbang init Example.java

This command creates the executable file Example.java.

$ ./Example.java
[jbang] Building jar...
Hello World

Here are the contents:

///usr/bin/env jbang "$0" "$@" ; exit $?


import static java.lang.System.*;

public class Example {

    public static void main(String... args) {
        out.println("Hello World");
    }
}

Editing a JBang script in your IDE §

Next, I then edited this script in IntelliJ IDEA:

$ jbang edit --open=idea Example.java

This command creates IntelliJ IDEA project that has a symbolic link to Example.java.

Adding dependencies §

The scripts, which process Markdown files, mainly used classes from java.nio.file.* and java.util.regex.*. However, one script generated Markdown files using Thymeleaf templates. It was remarkably easy to add the Thymeleaf dependency using the DEPS directive:

///usr/bin/env jbang "$0" "$@" ; exit $?

//DEPS org.thymeleaf:thymeleaf:3.1.1.RELEASE

After rerunning, jbang edit to update the IntelliJ IDEA project, I could write the Thymeleaf code.

Summary §

JBang makes it easy to write scripts using Java, which is statically typed and has sophisticated IDEs. But before feeling entirely comfortable with using JBang instead of Python, there are a couple of things I to do:

  1. Investigate how to edit JBang scripts that consist of multiple files - so far I’ve the scripts have inner classes, which are not reusable.

  2. Track down and evaluate the Java equivalents of Python libraries such as colorama, GitPython, argparse.


development  


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