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Measuring Java

rascal-0.40.17

Synopsis​

A few steps using the M3 model to compute basic metrics for a Java project in Eclipse.

Description​

This is a recipe for computing basic or more advanced metrics from a Java project in Eclipse. We assume:

  • You have Rascal installed in an Eclipse instance.
  • You have a Java project in your Eclipse workspace that compiles without errors. Let's call it HelloWorld.

Now we will follow the EASY paradigm:

  • A library will be used to parse the Java code generating Abstract Syntax Tree
  • The same library will generate a ((Rascal:Values/Relation))al model to represent interesting facts between Java source code artifacts
  • Then we can write queries over the generated trees and relations using Expressions.

These are a number of recipes for measuring different things about Java:

Examples​

First we import the basic data types for representing Java. The model is called M3, and its definition is split acros a generic language independent module called Core and a Java specific part called AST. Have a look at the documentation of these modules later. For now we will go through using them in a few examples.

rascal>import lang::java::m3::Core;
ok
rascal>import lang::java::m3::AST;
ok

"Snakes and Ladders" is an example Java project of which we have stored the source code in |tmp:///snakes-and-ladders/src|

rascal>|tmp:///snakes-and-ladders/src/snakes/|.ls
list[loc]: [
  |tmp:///snakes-and-ladders/src/snakes/SimpleGameTest.java|,
  |tmp:///snakes-and-ladders/src/snakes/Ladder.java|,
  |tmp:///snakes-and-ladders/src/snakes/LastSquare.java|,
  |tmp:///snakes-and-ladders/src/snakes/Game.java|,
  |tmp:///snakes-and-ladders/src/snakes/ISquare.java|,
  |tmp:///snakes-and-ladders/src/snakes/Snake.java|,
  |tmp:///snakes-and-ladders/src/snakes/Square.java|,
  |tmp:///snakes-and-ladders/src/snakes/FirstSquare.java|,
  |tmp:///snakes-and-ladders/src/snakes/Die.java|,
  |tmp:///snakes-and-ladders/src/snakes/DieTest.java|,
  |tmp:///snakes-and-ladders/src/snakes/Player.java|
]

Now we can extract our overview model:

rascal>myModel = createM3FromDirectory(|tmp:///snakes-and-ladders/src|);
M3: m3(
  |tmp:///snakes-and-ladders/src|,
  annotations={
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/Snake/squareLabel()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/Ladder/landHereOrGoHome()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/newGame()|,|java+class:///Test|>,
    <|java+method:///snakes/SimpleGameTest/move8jillWins(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/isFirstSquare()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/Ladder/squareLabel()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/FirstSquare/isOccupied()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/initialStrings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move4jillSnake(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/DieTest/testInRange()|,|java+class:///Test|>,
    <|java+method:///snakes/DieTest/testMinReached()|,|java+class:///Test|>,
    <|java+class:///snakes/SimpleGameTest|,|java+class:///RunWith|>,
    <|java+method:///snakes/SimpleGameTest/move2jackBackwards(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/DieTest/testMaxReached()|,|java+class:///Test|>,
    <|java+method:///snakes/SimpleGameTest/move5jackLadder(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move6jill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/enter(snakes.Player)|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/LastSquare/isLastSquare()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/FirstSquare/leave(snakes.Player)|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/move3jackMeetsJill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move2jillLadder(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move7jackBouncesBackToJill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move1jack(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/player()|,|java+interface:///java/lang/Override|>
  },
  typeDependency={
    <|java+method:///snakes/Game/winner()|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Game/winner()|,|java+class:///snakes/Player|>,
    <|java+parameter:///snakes/Player/joinGame(snakes.Game)/scope(game)/scope(0)/game|,|java+class:///snakes/Game|>,
    <|java+field:///snakes/Game/winner|,|java+class:///snakes/Player|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+primitiveType:///int|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+class:///snakes/Square|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+primitiveType:///int|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+class:///snakes/Square|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///java/lang/String|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///java/lang/Object|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/Game/initSquare(int,snakes.ISquare)|,|java+interface:///snakes/ISquare|>,
    ...

Some projects have extensive classpaths which the M3 extractor requires for accurate Java analysis. You can use this code to extract a classpath if the project is a Maven project:

rascal>import util::Reflective;
ok
rascal>cp = getProjectPathConfig(|tmp:///snakes-and-ladders|).javaCompilerPath;
list[loc]: [|file:///usr/share/apache-maven-3.8.8/boot/plexus-classworlds-2.6.0.jar|]

and then pass it into the M3 extractor (this project does not have dependencies)

rascal>myModel = createM3FromDirectory(|tmp:///snakes-and-ladders/src|, classPath=cp);
M3: m3(
  |tmp:///snakes-and-ladders/src|,
  annotations={
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/Snake/squareLabel()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/Ladder/landHereOrGoHome()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/newGame()|,|java+class:///Test|>,
    <|java+method:///snakes/SimpleGameTest/move8jillWins(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/isFirstSquare()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/Ladder/squareLabel()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/FirstSquare/isOccupied()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/initialStrings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move4jillSnake(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/DieTest/testInRange()|,|java+class:///Test|>,
    <|java+method:///snakes/DieTest/testMinReached()|,|java+class:///Test|>,
    <|java+class:///snakes/SimpleGameTest|,|java+class:///RunWith|>,
    <|java+method:///snakes/SimpleGameTest/move2jackBackwards(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/DieTest/testMaxReached()|,|java+class:///Test|>,
    <|java+method:///snakes/SimpleGameTest/move5jackLadder(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move6jill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/enter(snakes.Player)|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/LastSquare/isLastSquare()|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/FirstSquare/leave(snakes.Player)|,|java+interface:///java/lang/Override|>,
    <|java+method:///snakes/SimpleGameTest/move3jackMeetsJill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move2jillLadder(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move7jackBouncesBackToJill(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/SimpleGameTest/move1jack(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/FirstSquare/player()|,|java+interface:///java/lang/Override|>
  },
  typeDependency={
    <|java+method:///snakes/Game/winner()|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Game/winner()|,|java+class:///snakes/Player|>,
    <|java+parameter:///snakes/Player/joinGame(snakes.Game)/scope(game)/scope(0)/game|,|java+class:///snakes/Game|>,
    <|java+field:///snakes/Game/winner|,|java+class:///snakes/Player|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+primitiveType:///int|>,
    <|java+method:///snakes/Square/nextSquare()|,|java+class:///snakes/Square|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+primitiveType:///int|>,
    <|java+method:///snakes/Square/moveAndLand(int)|,|java+class:///snakes/Square|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///java/lang/String|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+interface:///snakes/ISquare|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///snakes/Game|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///java/lang/Object|>,
    <|java+method:///snakes/SimpleGameTest/move1strings(snakes.Game)|,|java+class:///Given|>,
    <|java+method:///snakes/Game/initSquare(int,snakes.ISquare)|,|java+interface:///snakes/ISquare|>,
    ...

Benefits​

  • Notice that all these Location literals are hyperlinks and you can click on them to go the source code that they point to. Try it!
  • M3 models are great for metrics, but also they are the basis for many other static analyses
  • See Measuring Classes and Measuring Methods for more benefits

Pitfalls​