Picocli: What to do for multiple commands

[NagendraHegde]

Hi Team,

Below is the situation I am facing:

I want to build a cli tool with picocli. I want to bundle it in a fat jar and give it to the users so that they can use it as a cli tool.

The tool is going to have multiple commands. Below is the format:

java commandone -a somevalue

java commandtwo -b someothervalue

For these, i can write classes for each individual commands with the help of @Command annotation.
e.g:
@Command(name="commandcone")
public class CommandOne implements Runnable { ... }

But the problem is, all the example given in the wiki demand to have public static void main() in the class and manually call CommandLine.run( ... ) in order to get the commands executed.

In the case of a tool having multiple commands (not subcommands), what do I do? I can not write main method to each class that i create for a command, right?

Do i manually write the routing for different commands? or is there a mechanism available already in picocli and I am unable to find it properly?

Please help. (btw other features are cool and you guys rock :) )

[remkop]

Hi @NagendraHegde , please take a look at this example:
https://github.com/remkop/picocli/blob/master/picocli-examples/src/main/java/picocli/examples/subcommands/ParentCommandDemo.java

It demonstrates how to code a top-level command with a single subcommand.
You can add more subcommands by adding them in the @Command(subcommands = {Aaa.class, Bbb.class, Ccc.class, ...}) list.

It is a good idea to make all your commands implement Runnable or Callable (either one is fine), then in your main method you can simply say:

CommandLine.run(new RunnableTopCommand(), args);

// or, if the top-level command implements Callable:
// CommandLine.call(new CallableTopCommand(), args);

Picocli will execute the most specific subcommand that the user specified. So, for example, if you have a command hierarchy like this:

top
  |
  +- sub
  |    |
  |    +- subsub
  |    
  +- sub2 
       |
       +- sub2sub

Then, when the user invokes top --option sub subsub --otheroption,
picocli will call run (or call) on the subsub subcommand (the most specific subcommand that the user specified.)

[remkop]

@NagendraHegde Did this answer your question?

[remkop]

@NagendraHegde Were you able to make progress or do you have follow-up questions?

[remkop]

@NagendraHegde Can this ticket be closed?

[remkop]

In the case of a tool having multiple commands (not subcommands), what do I do? I can not write main method to each class that i create for a command, right?

Since you are talking about top-level commands (not subcommands), every top-level command will need a separate class with its own main method to run it.

[remkop]

If your application has multiple top-level commands, each of these will need its own main method so it can be called from the commandline like this:

java -cp myjar.jar com.package.CommandOneClass -a somevalue
java -cp myjar.jar com.package.CommandTwoClass -b someothervalue

Your jar can only have one Main-Class in its manifest, and that will be the command when users invoke the jar as an application, like this:

java -jar myjar.jar -x somevalue

If you have multiple top-level commands, what people often do is provide multiple script files (shell script or batch scripts) that the end user can invoke. For example, for Windows:

# commandone.bat
java -cp myjar.jar com.package.CommandOneClass %*

This allows end users to call the command with its script name.
Build tools like gradle offer plugins that can generate these scripts for you.

[remkop]

Closing this ticket. Feel free to reopen if you want further clarification

[sebastienvermeille]

I have the same problem and I find the last comment more as a workaround than a real solution.

This jar will receive args[] so it has all what it needs to have in order to interprete parameters. I don't see why we should require some bash or batch scripts here.

Isn't there a better solution which could work with picocli without having to use a script ?

[remkop]

@sebastienvermeille, would you mind creating a new ticket to explain your use case?

[remkop]

@sebastienvermeille The OP never replied after multiple comments so it’s hard to say whether I understood their problem. I’m happy to help but it would be good if you could explain in your own words what it is you’re trying to achieve.

[sebastienvermeille]

@remkop sure if can help somehow I will :)
I create one right now with the more details I can give

[remkop]

@NagendraHegde I feel that I didn’t explain things very well in response to your question.

Please take a look at #641: perhaps my answer there is more clear and hopefully the discussion on that ticket is useful to you as well.