Motivation

This plugin runs JavaREPL within the context a Gradle build file. It configures the classpath used by javarepl to resolve classes to include all testRuntime dependencies, as well as, the compile and test artifacts for this project. Using this plugin, developers can easily explore and execute different aspects of their projects via a REPL.

The following is a sample of the plugin output:

➜ gradle-javarepl-plugin git:(jsb/release-1.0.0) ✗ ./gradlew --no-daemon --console plain javarepl
:compileJava NO-SOURCE
:processResources
:classes
:compileTestJava NO-SOURCE
:processTestResources NO-SOURCE
:testClasses UP-TO-DATE
:javarepl


Welcome to JavaREPL version 428 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_92)
Type expression to evaluate, :help for more options or press tab to auto-complete.
Connected to local instance at http://localhost:63534
java>

Installation

N.B. This plugin requires JDK 8+. Java 7 and below are not supported.

Adding the following block to a build.gradle installs this plugin:

    plugins {
        id 'net.cockamamy.gradle.javarepl'
    }

If the java plugin has not been applied when this plugin is invoked, it will be applied automatically.

Configuration

The plugin adds a javarepl extension namespace with the following options:

Extension Property	Description	Default Value
configurations	The list of Gradle configurations from which the classpath used to run Java REPL is derived	["testRuntime"]
dependsOn	The task on which the javarepl tasks depends for execution	testClassses
heapSize	The heap size used to run JavaREPL	null
timeout	The length of time to run Java REPL before killing it. This parameter is primarily use by unit tests.	null
stackSize	The stack size used to run JavaREPL	null
version	The version of Java REPL to install	428

Running

Normally, Gradle will attempt to use an existing daemon to speed up builds. Unfortunately, this feature prevents interactive console applications such as JavaREPL from running properly. Therefore, Gradle should be started with the --no-daemon commmand line option when running the javarepl task. In addition to the daemon issue, Gradle's rich console can interfere with the JavaREPL's operations. Running the task with the --console plain option will disable the rich console to avoid these potential issues. The following is an example command line to properly execute the javarepl task:

./gradlew javarepl --no-daemon --console plain

To reduce the overhead to typing this command line regularly, it is suggested that users add the following alias to their shell profile:

alias grel='./gradlew javarepl --no-daemon --console plain'

With this alias, the grepl command will start a Java REPL using Gradle.

Manual Testing

The test-repl.sh script is provided to run development builds of the plugin for manual testing purposes.

Known Issues

Quiting JavaREPL, either by using the :quit command or CTRL-C, causes the following stack trace:

Exception in thread "main" java.lang.RuntimeException: { expected, j encountered.
	at javarepl.internal.totallylazy.parser.Failure.exception(Failure.java:76)
	at javarepl.internal.totallylazy.parser.Failure.value(Failure.java:72)
	at javarepl.internal.totallylazy.json.Json.map(Json.java:20)
	at javarepl.client.JavaREPLClient.execute(JavaREPLClient.java:72)
	at javarepl.Main.main(Main.java:66)

This exception is spurious and does not cause any problems.