Groovysh Server

Introduction

If you are familiar with groovy, you know what groovysh is. It's damn simple REPL (read, evaluate, print, loop) shell for evaluating groovy code. And groovy-shell-server is full featured groovy shell inside your application.

How many times you are in situation when all you need is to call some method inside your application, but the only way to do it is JMX or custom user interface (web page, for instance)? Groovy shell server allows you to run REPL shell inside your application and work with it like you are using groovysh.

Groovy shell server uses groovysh API inside, so all features of groovysh (autocompletion, history etc.) are supported.

Installation

Just include following dependency in your pom.xml:

<dependency>
	<groupId>me.bazhenov.groovy-shell</groupId>
	<artifactId>groovy-shell-server</artifactId>
	<version>2.2.1</version>
</dependency>

Using

In your application you should start GroovyShellService:

GroovyShellService service = new GroovyShellService();
service.setPort(6789);
service.setBindings(new HashMap<String, Object>() {{
	put("foo", obj1);
	put("bar", obj2);
}});

service.start();

And destroy it on application exit:

service.destroy();

As of 1.5 Groovy shell server use plain ssh as a client. So connecting to a groovy shell server as simple as:

$ ssh 127.1 -p 6789
Groovy Shell (2.1.9, JVM: 1.6.0_65)
Type 'help' or '\h' for help.
-------------------------------------------------------------------------------
groovy:000> (1..10).each { println "Kill all humans!" }
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
Kill all humans!
===> 1..10
groovy:000>

By default, no authentication is required (any username is allowed to open a SSH connection). You can enable password authentication by creating your own implementation of org.apache.sshd.server.PasswordAuthenticator interface and passing an instance to server:

PasswordAuthenticator myPasswordAuthenticator = new MyPasswordAuthenticator();
service.setPasswordAuthenticator(myPasswordAuthenticator);

Integrating with Spring

You can easily integrate Groovy Shell with Spring container:

<bean class="me.bazhenov.groovysh.spring.GroovyShellServiceBean"
	p:port="6789"
	p:launchAtStart="true"
	p:publishContextBeans="true"
	p:bindings-ref="bindings"/>

<u:map id="bindings">
	<entry key="foo" value="bar"/>
</u:map>

When publishContextBeans is true all context beans are published to groovy shell context. So bean with id foo will be available as foo in groovy shell. Also reference to the ApplicationContext is added to bindings implicitly as ctx. So in shell you can get objects from container by id or type (e.g. ctx.getBean('id')).

It is also possible to enable password authentication by setting passwordAuthenticator property on GroovyShellServiceBean.

Simple run

In order to simple run applications you can use maven-exec plugin:

mvn -f groovy-shell-server/pom.xml exec:java -Dexec.mainClass=me.bazhenov.groovysh.Main

Management

What if a well-meaning developer fires up a remote shell and accidentally executes a script which hammers the server? Fortunately, each GroovyShellService instance registers itself with the default MBeanServer and provides a "killAllClients" operation to kill any open client sockets and stop the associated client threads. Thus you can connect with jconsole or your favorite JMX frontend to resolve this issue if it arises.

Build

Use maven-assembly plugin to build and create archive of groovy-shell-server:

mvn package

Archives will be placed in groovy-shell-server/target/.

Deploy

Deploying to Maven Central:

mvn clean deploy

On Java 16 following variable should be exported:

MAVEN_OPTS="--add-opens=java.base/java.util=ALL-UNNAMED\
	--add-opens=java.base/java.lang.reflect=ALL-UNNAMED\
	--add-opens=java.base/java.text=ALL-UNNAMED\
	--add-opens=java.desktop/java.awt.font=ALL-UNNAMED"