Gradle to execute Java class without modifying build gradle

Question

There is simple Eclipse plugin to run Gradle  that just uses command line way to launch gradle   What is gradle analog for maven compile and run mvn compile exec java -Dexec mainClass example Example  This way any project with gradle build could be run   UPDATE  There was similar question What is the gradle equivalent of maven  39 s exec plugin for running Java apps  asked before  but solution suggested altering every project build gradle  package runclass   public class RunClass       public static void main String   args            System out println  app is running               Then executing gradle run -DmainClass runclass RunClass   run FAILED  FAILURE  Build failed with an exception     What went wrong  Execution failed for task   run    gt  No main class specified

User · Answer

You just need to use the Gradle Application plugin:

apply plugin:'application'
mainClassName = "org.gradle.sample.Main"

And then simply gradle run.

As Teresa points out, you can also configure mainClassName as a system property and run with a command line argument.

User · Answer

There is no direct equivalent to mvn exec java in gradle  you need to either apply the application plugin or have a JavaExec task   application plugin  Activate the plugin   plugins       id  application              Configure it as follows   application       mainClassName   project hasProperty  mainClass     getProperty  mainClass      NULL      On the command line  write    gradle -PmainClass Boo run   JavaExec task  Define a task  let s say execute   task execute type JavaExec       main   project hasProperty  mainClass     getProperty  mainClass      NULL     classpath   sourceSets main runtimeClasspath     To run  write gradle -PmainClass Boo execute  You get    gradle -PmainClass Boo execute  compileJava  compileGroovy UP-TO-DATE  processResources UP-TO-DATE  classes  execute I am BOO    mainClass is a property passed in dynamically at command line  classpath is set to pickup the latest classes     If you do not pass in the mainClass property  both of the approaches fail as expected     gradle execute  FAILURE  Build failed with an exception     Where  Build file  xxxx build gradle  line  4    What went wrong  A problem occurred evaluating root project  Foo    gt  Could not find property  mainClass  on task   execute

User · Answer

Expanding on First Zero s answer  I m guess you want something where you can also run gradle build without errors    Both gradle build and gradle -PmainClass foo runApp work with this   task runApp type JavaExec        classpath   sourceSets main runtimeClasspath      main   project hasProperty  mainClass     project getProperty  mainClass      package MyDefaultMain      where you set your default main class

User · Answer

You can parameterise it and pass  gradle clean build -Pprokey goodbye  task choiceMyMainClass type  JavaExec         group    Execution      description    Run Option main class with JavaExecTask      classpath   sourceSets main runtimeClasspath      if  project hasProperty  prokey             if  prokey     hello                main    com sam home HelloWorld                     else if  prokey     goodbye                main    com sam home GoodBye                  else               println  Invalid value is enterrd              println  Invalid value is enterrd   project prokey

[java] Gradle to execute Java class (without modifying build.gradle)

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