SpeADL for Dynamic Architectures Tutorial¶

This is a tutorial for SpeADL: understanding ecosystems and species, defining a simple ecosystem, composing species together with uses.

Objectives¶

The objective of this tutorial to understand the abstractions of species and uses.

We will create a Logging ecosystem that contains Logger species.
Then we will create a Banking ecosystem that contains Account species that need to log what happens.
Finally we will create a Bank ecosystem that compose Account species with Logger species thanks to the use abstraction.

Prerequisites¶

It is needed to understand the content of the SpeADL⁻ tutorial before doing this one.

Creating a New Project and Organisation¶

Create a Java project.
We will use again an organisation of the package and namespaces as explained in this best practice.

The Logging Ecosystem¶

Logging will be an ecosystem, and its particularity is that it will be able to create Loggers: while logging is the subsystem responsible of all logging, each logger will be responsible of logging one particular aspect of the system identified by a name.
We will have multiple implementation for the Logging ecosystem:

• One with only one file where to log with each line prepended with the name.
• One with one file per Logger all in the same directory.

Organisation¶

Create the following hierarchy of packages:

• tutorial2.logging
  • impl
  • interfaces

Defining the Ecosystem and the Species¶

Create a SpeADL file named filesystem.speadl in the package tutorial2.filesystem.

Define in it the ecosystem and the species in the right namespace as well as the needed interface:

import tutorial2.filesystem.interfaces.ILog

namespace tutorial2.filesystem {

    ecosystem Logging {
        species Logger(name: String) {
            provides log: ILog
        }
    }

}

package tutorial2.filesystem.interfaces;

public interface ILog {

    public void addLine(String line);
}

Implementing the Ecosystem and the Species, First One¶

Create a new Java class in tutorial2.logging.impl named LoggingImplOne that extends Logging, that takes the a File as a parameter to the constructor to store the logs, and resolve the error with the Quick Fixes of Eclipse:

package tutorial2.logging.impl;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;

import tutorial2.logging.Logging;

public class LoggingImplOne extends Logging {

    private PrintWriter logWriter;

    public LoggingImplOne(File logFile) {
        // if an exception happens, nothing can be done about it
        // we just let logStream be null and
        // the operations of logging won't be done
        try {
            logFile.createNewFile();
            this.logWriter = new PrintWriter(logFile);
        } catch (FileNotFoundException e) {
            this.logWriter = null;
        } catch (IOException e) {
            this.logWriter = null;
        }
    }

    @Override
    protected Logger make_Logger(String name) {
        // TODO Auto-generated method stub
        return null;
    }
}

As we can see, the species we defined needs to be implemented and this implementation needs to be returned by the method Logger make_Logger(String name).

Let's define an inner class inside LoggingImplOne to do that, it will take as a parameter to the constructor the name of the Logger and that will exploit the logWriter to do the actual logging.

public class LoggingImplOne extends Logging {

    private PrintWriter logWriter;

    // ...

    @Override
    protected Logger make_Logger(String name) {
        return new LoggerImpl(name);
    }

    private class LoggerImpl extends Logger implements ILog {

        private final String name;

        public LoggerImpl(String name) {
            this.name = name;
        }

        @Override
        protected ILog make_log() {
            return this;
        }

        @Override
        public void addLine(String line) {
            logWriter.println("["+name+"] "+ line);
        }
    }
}

Implementing the Ecosystem and the Species, Second One¶