jPeek is a cohesion analizator of Java projects.

What this repository is for?

This repository proposes cohesion metrics that were written in EO and integrated in the original Jpeek project.

How to use

Java

First, you need to install Java Development Kit (JDK) on your machine in order to build and work with JPeek. Version 11 of JDK would be a good option (you can find installation packages here).

Downloading sources

Second, fork this repository with git:

git clone git@github.com:HSE-Eolang/jpeek.git

or just download the project code from here and unzip the archive.

Building the project

Then, command Maven to build the JPeek project (by the way, you do not need to install Maven, it is already packaged within the repository):

./mvnw clean package

On Windows, use mvnw.cmd instead of mvnw.

Running JPeek

When the build is finished, you can use JPeek by playing with the sources of itself:

java -jar target/jpeek-jar-with-dependencies.jar --sources target/. --target ./jpeek_output --metrics EO_LCOM1,EO_LCOM2,EO_LCOM3,EO_LCOM4,EO_LCOM5,EO_SCOM,EO_NHD,EO_OCC,EO_PCC,EO_TCC,EO_LCC,EO_CCM

jPeek will analyze Java classes (*.class files) in the --sources directory (here, it is target/.) and write the resulting report to the --target directory. In this example, the report will be generated in the ./jpeek_output directory.

Metrics to be calculated are listed after the --metrics argument key. The full list of metrics implemented in EO can be found here.

Cohesion Metrics

The following Jpeek metrics are implemented using EO:

• EO_LCOM1
• EO_LCOM2
• EO_LCOM3
• EO_LCOM4
• EO_LCOM5
• EO_OCC
• EO_PCC
• EO_LCC
• EO_TCC
• EO_CCM
• EO_CAMC
• EO_NHD
• EO_SCOM

For extra information about formulas and implementing details, check this document.

How it works?

First, Skeleton parses Java bytecode using Javaassit and ASM, in order to produce skeleton.xml. This XML document contains information about each class, which is necessary for the metrics calculations. For example, this simple Java class:

class Book {
  private int id;
  int getId() {
    return this.id;
  }
}

Will look like this in the skeleton.xml:

<class id='Book'>
  <attributes>
   <attribute public='false' static='false' type='I'>id</attribute>
  </attributes>
  <methods>
    <method abstract='false' ctor='true' desc='()I' name='getId' public='true' static='false'>
      <return>I</return>
      <args/>
    </method>
  </methods>
</class>

Then, we have a collection of EO classes, one per each metric. For example, EO_lcom1.eo transforms skeleton.xml into LCOM1.xml, which may look like this:

<metric>
  <title>LCOM1</title>
  <app>
    <class id='InstantiatorProvider' value='1'/>
    <class id='InstantationException' value='0'/>
    <class id='AnswersValidator' value='0.0583'/>
    <class id='ClassNode' value='0.25'/>
    [... skipped ...]
  </app>
</metric>

Known Limitations

• The java compiler is known to inline constant variables as per JLS 13.1. This affects the results calculated by metrics that take into account access to class attributes if these are final constants. For instance, all LCOM* and *COM metrics are affected.
• Class constructors, static and private methods are not taken into account by default.

How to contribute?

Just fork, make changes, run mvn clean install and submit a pull request;

Contributors of current solution

• @wsngit as Ivan Spirin
• @nlchar as Eugene Popov
• @aventador3000 as Vitaliy Korzun
• @jizzel as Joseph A. Attakorah
• @hadiSaleh as Hadi M. Saleh