Java Fundamentals - I/O 2 Homework

Description

Your task is to finish a Java program which outputs system info as XML and JSON files. Complete the implementation of SystemDumpImpl that implements the following interface:

public interface SystemDump {

  /**
   * @return current system dump info.
   */
  Info newInfo() throws Exception;

  /**
   * Write given data into a file as XML.
   */
  void writeXml(Info src, Path dest) throws Exception;

  /**
   * Write given data into a file as JSON.
   */
  void writeJson(Info src, Path dest) throws Exception;

}

public interface Info {

  /**
   * @return sorted map of all environment variables.
   */
  Map<String, String> getSystemEnvironment();

  /**
   * @return sorted map of all system properties.
   */
  Map<String, String> getSystemProperties();

  /**
   * @return output of a system-dependent command line tool giving some system info.
   *  On Windows: <code>cmd /c ver</code>
   *  On others: <code>uname -a</code>
   */
  String getSystemVersion();

}

The project has a set of unit tests. To get the maximum points all those tests must pass. Existing tests cannot be altered, but new ones can be added.

Requirements

1. Both Maps have to be sorted A-Z by keys.
2. Execute a proper command line tool depending on the OS and gather its output.
3. Use XML and JSON APIs of your choice (don't write a String directly).
4. Buffer data for better performance.
5. Close all resources properly.
6. The program must work on Windows, Linux and macOS.

Example JSON

{  
   "systemEnvironment":{  
      "HOME":"/Users/mati",
      "MAVEN_OPTS":"-Xmx1024M"
   },
   "systemProperties":{  
      "java.specification.name":"Java Platform API Specification",
      "path.separator":":"
   },
   "systemVersion":"Darwin Stalker.local 15.6.0 Darwin Kernel Version 15.6.0: Mon Aug 29 20:21:34 PDT 2016; root:xnu-3248.60.11~1/RELEASE_X86_64 x86_64\\n"
}

Example XML

<systemDump>
  <systemEnvironment>
    <entry key="HOME">/Users/mati</entry>
    <entry key="MAVEN_OPTS">-Xmx1024M</entry>
  </systemEnvironment>
  <systemProperties>
    <entry key="java.specification.name">Java Platform API Specification</entry>
    <entry key="path.separator">:</entry>
  </systemProperties>
  <systemVersion>
    Darwin Stalker.local 15.6.0 Darwin Kernel Version 15.6.0: Mon Aug 29 20:21:34 PDT 2016; root:xnu-3248.60.11~1/RELEASE_X86_64 x86_64\n
  </systemVersion>
</systemDump>

Various tips

1. You can use JAXB to output XML, but due to the way tests are built you then need to wrap the Info object passed to SystemDump::writeXml with your own JAXB annotated class and then delegate all of the calls to get the data to the wrapped object. Otherwise you can get the following exception:

   javax.xml.bind.JAXBException: class org.zeroturnaround.jf.sysdump.test.InfoImpl nor any of its super class is known to this context.

   This is actually a well known design pattern called Decorators. For more info on decorators you can read this blog post. You can apply the same principle to have a decorator with JAXB annotations.

2. If you want to build the distribution zip without fixing the tests, then you can do that by skipping tests in the build by adding -DskipTests to the command:

   ./mvnw clean deploy -DskipTests

   However, note that to get the full score for this assignment, you still need to make the tests pass correctly.

Submitting your assignment

For your convenience, we have set up the Maven project to ZIP up all files in your project folder so it is easy for you to attach it to an e-mail and send it our way. All you need to do is to execute the following command in your project folder:

./mvnw clean deploy

It will ask you for your full name, Student Book Number (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:1.8:run (package homework ZIP) @ homework4 ---
[INFO] Executing tasks

main:
Your full name (e.g. John Smith):
Jane Smith
Your Student Book Number (matrikli number, e.g. B12345):
B12345
Comment:
Java IO
      [zip] Building zip: /Users/jane/workspace/jf-hw-sysdump/target/jf-homework4-B12345.zip
   [delete] Deleting: /Users/jane/workspace/jf-hw-sysdump/homework.properties
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 20.041 s
[INFO] Finished at: 2017-02-03T11:35:11+02:00
[INFO] Final Memory: 21M/283M
[INFO] ------------------------------------------------------------------------

After Maven has finished, you can find the generated ZIP file in target folder with name such as jf-homework5-B12345.zip (it contains your Student Book Number/matrikli number and homework number).

The only thing left to do now is to send the ZIP file as an attachment to an e-mail with subject "Homework 5 - your Student Code/maktrikli number" to jf@zeroturnaround.com.