For running an agent, you must launch this agent on the runtime environment. This document explains how to launch an agent on the Janus platform from the command line.
Three methods could be used for launching an agent with Janus:
The SARL project provides a command-line tool for launching agents on the Janus runtime environment.
You could download this command line tool, named “janus” on the downloading page of SARL.
For launching an agent, you must launch the command-line tool with the fully-qualified
name of the agent as parameter, myapp.MyAgent
in the following example.
janus myapp.MyAgent
The janus command-line tool provides options that will enable you to tune the launching configuration:
janus --help
One of the command-line options that is usually mandatory is the –jar option, which enables you to specify the jar files that contains your application:
janus --jar path/to/myapp.jar myapp.MyAgent
If the janus
script indicates to you an error “agent not found”, most of the time it is because your application’s jar file is not on the class path.
The –jar option becomes mandatory for specifying the jar file.
The Janus platform provides a Boot
class. For launching the platform, you must execute this
boot class in a Java Virtual Machine.
The typical command line is:
java -cp app.jar io.sarl.sre.boot.Boot
The option -cp
specifies the Jar file that contains
the compiled classes. The given app.jar
file is a Jar file that is containing the Janus
platform, the SARL libraries, and the application classes.
The last argument is the fully qualified name of the booting class of Janus: io.sarl.sre.boot.Boot
The example given in the previous section causes an error. Indeed, it is mandatory to specify the fully qualified name of the agent to launch:
java -cp app.jar io.sarl.sre.boot.Boot myapp.MyAgent
Very Important Note The Janus platform allows to start only one agent from the command line. If you want to start a collection of agents, you must select one of the following approaches: * launch a separate Janus platform instance for each agent, or * launch an agent that is spawning the other agents.
In the previous section, we assume that all the application binary files are
contained into the app.jar
file.
You may replace the app.jar
in the previous command lines by the classpath
that is containing all the jar files required for running your application, including
the Janus jar file(s):
java -cp /path/to/myapplication.jar:/path/to/io.janusproject.kernel-<version>-with-dependencies.jar io.sarl.sre.boot.Boot myapp.MyAgent
The io.janusproject.kernel-<version>-with-dependencies.jar
file may be dowloaded from the Janus website
You may also create the app.jar
file with Maven by using the assembly plugin for creating a jar file with all the dependencies inside.
To do so, you have to update the pom.xml
file of your project and to define the assembly specification.
The content of the pom.xml
must include the assembly plugin definition:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<version>3.3.0</version>
<executions>
<execution>
<id>make-assembly-with-deps</id>
<phase>package</phase>
<goals>
<goal>single</goal>
</goals>
<configuration>
<descriptors>
<descriptor>with-dependencies.xml</descriptor>
</descriptors>
</configuration>
</execution>
</executions>
</plugin>
The previous definition mentions the file with-dependencies.xml
that contains the assembly specification.
The content of this file could be:
<assembly xmlns="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/plugins/maven-assembly-plugin/assembly/1.1.0 http://maven.apache.org/xsd/assembly-1.1.0.xsd">
<id>with-dependencies</id>
<formats>
<format>jar</format>
</formats>
<includeBaseDirectory>false</includeBaseDirectory>
<dependencySets>
<dependencySet>
<unpack>true</unpack>
<scope>runtime</scope>
</dependencySet>
</dependencySets>
<containerDescriptorHandlers>
<!-- Merge service description's files in a proper way -->
<containerDescriptorHandler>
<handlerName>metaInf-services</handlerName>
</containerDescriptorHandler>
</containerDescriptorHandlers>
</assembly>
The tag containerDescriptorHandlers
is very important to be present into the definition.
Without this tag, the SARL and Janus services will not be correctly merged into the
generated Jar file with all the dependencies.
Caution You must use the version 3.3.0 (or higher) of maven-assembly-plugin
to have access to the mentioned capability.
The Janus platform provides a collection of command line options. For obtaining the list of these options, you should type:
java -cp app.jar io.sarl.sre.boot.Boot --help
Maven provides a plugin for launching an application after automatically building the application’s classpath. This plugin may be used for launching an agent.
Based on the fact that the Janus platform provides a Boot
class for launching itself,
you may use the Maven execution plugin for classing this booting class.
The typical command line is:
mvn exec:exec -Dexec.executable=java -Dexec.args="-cp %classpath io.sarl.sre.boot.Boot"
The option -Dexec.executable
specifies the Java executable.
The option -Dexec.args
contains the command line arguments to pass to Java.
The first argument is the classpath of the project. You must not change %classpath
because it will be dynamically
replaced by the Maven plugin.
The example given in the previous section causes an error. Indeed, it is mandatory to specify the fully qualified name of the agent to launch:
mvn exec:exec -Dexec.executable=java -Dexec.args="-cp %classpath io.sarl.sre.boot.Boot <qualified_name_of_the_agent>"
Very Important Note The Janus platform allows to start only one agent from the command line. If you want to start a collection of agents, you must select one of the following approaches: * launch a separate Janus platform instance for each agent, or * launch an agent that is spawning the other agents.
The Janus platform provides a collection of command line options. For obtaining the list of these options, you should type:
mvn exec:exec -Dexec.executable=java -Dexec.args="-cp %classpath io.sarl.sre.boot.Boot --help"
In the next section, we will learn how to launch your SARL project from a Java program or a SARL class.
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