Console application with Java and gradle

Question

I am writing a console application with Java and gradle. I am using the application plugin and have the required fields correctly configured in build.gradle.

In my main class I have BufferedReader linked with System.in. Here's the problem: When I run gradle run in project directory, the reader does not wait for my console input. BufferedReader#readLine instead returns null on the very first call. This behavior is not desirable for what am I doing.

What is the solution? Is there a separate console application plugin for gradle or do I need to tweak application plugin somehow to suit my needs?

4 years later! If you are running a Windows OS, I have just found that by running the task from a Cygwin terminal this annoying "> Building ..." stuff does not appear. But I've also found that putting `standardInput = System.in` only works for me if I put it inside a specially defined `task`, not when inside `run`. — mike rodent, Oct 25 '16 at 18:52
Related Gradle issues: https://github.com/gradle/gradle/issues/1251 and https://github.com/gradle/gradle/issues/2842 — jcsahnwaldt Reinstate Monica, Mar 18 '21 at 13:40

score 110 · Accepted Answer · edited May 09 '22 at 11:05

110

By default, the system.in of your Gradle build is not wired up with the system.in of the run (JavaExec) task. You can do the following:

build.gradle (Groovy syntax):

run {
    standardInput = System.in
}

build.gradle.kts (Kotlin DSL syntax):

tasks.named<JavaExec>("run") {
    standardInput = System.`in`
}

edited May 09 '22 at 11:05

Mahozad

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answered Nov 01 '12 at 07:13

Rene Groeschke

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3

Thank you! That was a great help. Now is there a way to avoid printing `> Building > :run` when it prompts user for next input? – missingfaktor Nov 01 '12 at 07:15
4

unfortunately not at the moment. I've raised an issue for that a while ago: http://issues.gradle.org/browse/GRADLE-1147 you can vote for it. – Rene Groeschke Nov 01 '12 at 07:21
Thank you, again. This too will do. Accepting your answer. :) – missingfaktor Nov 01 '12 at 07:21
2

I tried the same exact thing but Gradle gets stuck and no input gets printed to command line if I type. Am I doing something wrong? – Giovanni Botta Mar 21 '14 at 19:48
1

I have a [SO](http://stackoverflow.com/questions/22567831/gradle-execute-groovy-interactive-shell-with-project-classpath) for that. – Giovanni Botta Mar 21 '14 at 19:49
If using the Kotlin dsl you need to escape the `in` since it is a keyword in Kotlin. Use backticks like so: ``standardInput = System.`in` `` – checketts Feb 05 '20 at 22:15
2

Use `--console=plain` so nothing gets printed after asking for input – Alireza Ahmadi Jul 13 '21 at 14:18

score 35 · Answer 2 · edited Nov 19 '18 at 03:51

35

As stated above, add

run {
   standardInput = System.in
}

And run:

gradle console:run -q --console=plain

where:

-q runs task in "quiet" mode (to avoid having > Building > :run)
--console=plain drops execution status: <=-> 80% EXECUTING [TIME]

Source: https://docs.gradle.org/current/userguide/gradle_command_line.html

edited Nov 19 '18 at 03:51

iluu

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answered Jun 09 '16 at 22:25

loeschg

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this execution status spoils output when I want to use carriage return (it duplicates on each line). do you know how to disable it without --console=plain because it also disables carriage return processing – Yevhenii Nadtochii Nov 05 '19 at 17:55

score 4 · Answer 3 · answered Nov 20 '20 at 14:32

4

For build.gradle.kts:

tasks.getByName<JavaExec>("run") {
    standardInput = System.`in`
}

answered Nov 20 '20 at 14:32

diralik

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score -4 · Answer 4 · answered Nov 01 '12 at 06:48

-4

Chances are, the problem lies in your java code. All the application plugin does is compile the java code, and run the main class that you specify. Can you post the code in your main class that you specified for the application plugin (mainClassName) ?

answered Nov 01 '12 at 06:48

CaTalyst.X

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I ran the code from within IntelliJ IDEA as well. (By right-clicking the file and selecting `Run .main`.) It works just fine there. – missingfaktor Nov 01 '12 at 06:52

Console application with Java and gradle

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