Java Fundamentals - Classloaders Homework

Description

Here we've implemented a very simple plugin system. We have a Plugin interface that defines that every plugin has a name, URL and a logo. The plugins are defined in the folder plugins in the project.

Each plugin has a README.properties (that defines the plugin information) and the corresponding class file in that folder.

Our custom class loader picks that class up and instantiates. We call these plugins our local plugins.

Your task

Write a custom classloader and all necessary logic to support remote plugins. Remote plugins adhere to the same interface but they are accessible from the interwebs.

The plugins are hosted at https://github.com/zeroturnaround/jf-hw-classloaders/tree/master/plugins-remote I have hardcoded the locations of the 3 plugins into the homework.

The plugin meta information is in the README.properties file of each plugin. The plugin class files are hidden inside PNG files in the same folder and your task is to find, extract and define classes from those very same images.

Just to reiterate. The bytes of the classes that define the plugins are somewhere in the PNG files. Once you've implemented your solution the org.zeroturnaround.jf.hw.classloaders.Main program should run without any errors and print out all remote plugins (currently only prints names and null values). We've also provided empty implementations of RemotePluginManager and RemotePluginLoader. There is also a unit test that will start to pass after you've implemented the methods correctly. I will evaluate the correctness of the homework based on the output of the Main method.

I've also implemented a helper method RemotePluginManager.loadPropertiesFile(URL url). You can use this to load remote properties files.

Happy hacking!

Submitting your assignment

When you have gotten the test passing and the build to succeed, you can submit your assignment by first running the following command in the homework root folder:

./mvnw clean deploy

It will ask you for your full name, Student Code (also known as matrikli number) and a comment (optional).

Example:

./mvnw clean deploy

#...skipping building, testing and packaging output from Maven...

[INFO] --- maven-antrun-plugin:1.7:run (package homework ZIP) ---
[INFO] Executing tasks

main:
Your full name (e.g. John Smith):
Jane Smith
Your Student Code (matrikli number, e.g. ABCD012345):
ABCD012345
Comment:
Java IO
      [zip] Building zip: /Users/lanza/Projects/java/jf/jf-homeworkX/target/jf-howeworkX-ABCD012345.zip
   [delete] Deleting: /Users/lanza/Projects/java/jf/jf-homeworkX/homework.properties
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 45.028s
[INFO] Finished at: Thu Aug 28 15:36:19 EEST 2014
[INFO] Final Memory: 17M/99M
[INFO] ------------------------------------------------------------------------

After Maven has finished and the build was successful, you can find a ZIP file at target/jf-homeworkX-ABCD012345.zip (the name of the zip file contains the homework number and your Student Code/matrikli number).

This ZIP file contains all the files that we need to check your homework. The only thing left to do now is to send the ZIP file as an attachment to an e-mail with subject "Homework X - your Student Code/maktrikli number" to [email protected].