ftomassetti / effectivejava

Run queries on your Java code to check if it meets the criteria suggested by the book Effective Java. And some others.

effectivejava

Effective java is a tool to examine your Java codebase. You can use it in three different ways:

• as a Java linter. Just tells it which directory you want to examine, it will spit out a set of warnings and suggestions to improve your code
• run queries from the command line. It could tell you which type of Singleton you are using in your codebase or how many constructors have 10 or more parameters. This modality can be easily integrated with other tools
• run queries interactively. It permits to poke your codebase, parsing it once and running different queries to find out interesting facts about it.

The project is named effectivejava because many queries/checks derive from reading the book Effective Java. Others will be implemented as well (feel free to suggest your favorite ones!).

While reading that book I thought that yes, many principles are well known, but they are rarely applied to a large codebase. I thought that applying them in practice is much harder than it seems, and a tool like this one could help in improving constantly a codebase.

Which is the easiest way to install it?

Download the standalone jar from the releases page. No deps needed, everything is packed inside the jar. Feel free to rename it (effectivejava-0.1.0-SNAPSHOT-standalone.jar is a mouthful...)

Linting mode: how to use it

Just run:

# this generate a jar file
lein jar
# note that 0.1.3 is the current version it could change in the future
java -jar effectivejava-0.1.3-SNAPSHOT-standalone.jar -l -d "<myJavaProjectDir>"

You can expect a set of lines like this one:

org.springframework.jdbc.core.SqlInOutParameter : This class has too many constructors (7). Consider using static factory methods or the Builder pattern

If you run this command from the root of your codebase you can avoid the -d option.

CLI mode: how to use it

Now, suppose you want to know which classes has 5 or more constructor; you can run this command:

java -jar effectivejava-0.1.3-SNAPSHOT-standalone.jar -q mc -d "<myJavaProjectDir>" -t 5

You can expect a similar output:

Considering 109 Java files
japa.parser.ast.expr.ArrayCreationExpr  :  5
japa.parser.ast.body.MethodDeclaration  :  5
japa.parser.ast.body.BaseParameter  :  5
japa.parser.ast.body.FieldDeclaration  :  5

Interactive mode: how to use it (Work in progress!)

You can launch interactive mode with the -i option.

java -jar effectivejava-0.1.3-SNAPSHOT-standalone.jar -i

A typical interaction could be this one:

> load "."
Loading .
Java files loaded: 440
> mc th 5
Command not implemented:  :MC

As you can read from the last line, while the main logic for the interactive mode is there we still miss a few bits :) It will be corrected soon.

What queries can you run

I am just getting started so I implemented only a few queries for now:

• mc=many constructors: find the classes which contain the same number of constructors as the given threshold, or more
• mcp=many constructor parameters: find the constructors which contain the same number of parameters as the given threshold, or more
• st=singleton type: find if a type implements the singleton pattern and distinguish between the three types (public field, static factory, singleton enum)
• u=utils classes: find classes having only static methods and verify they have exactly one private constructor taking no parameters

Effective Java (the book) items implemented

Item	Status
Item 1	Done
item 2	TODO
item 3	Done
item 4	Done
item 5	TODO
item 6	TODO
item 7	Done
item 8	Planned for v0.2
item 9	Planned for v0.2
item 10	Done
item 11	TODO
...item 78	TODO

Dev info

The project is written in Clojure using a java library called JavaParser.

You will need also Leiningen, the build tool for Clojure. It should download also Clojure for you.

Dev guidelines

To monitor code quality we use kibit and eastwood.

When running eastwood exclude the check for unlimited use of namespaces:

lein eastwood "{:exclude-linters [:unlimited-use]}"

To verify the code is correctly formatted cljfmt is used. You can run it like this:

# to verify possible style issues
lein cljfmt check
# to automatically fix them
lein cljfmt fix

We use lein-ancient to verify our dependencies are up-to-date.

What is the link with the book?

I am reading this book and many advices seem sort of obvious in theory but I guess there are some violations lurking in the large codebase I am working with. I was curious to assess how many violations there were and I needed a way to find them out automatically. And I wanted to learn Clojure. And I had a free sunday. So...

What else

Hope you enjoy this small project of mine. Feel free to open issues and ask questions!

Contributors

David Ortiz is a regular contributor: he started fixing bugs, setting up Travis and it is contributing many other improvements.

effectivejava's Issues

Issue 11: Avoiding Cloneable

It is best for interface to not extend it and for not final classes to not implement it

Item 10: override toString

Check every class override it (or a superclass different from Object does it)

Java linter modality

Implement and document it

Build a symbol solver

Javaparser does not solve symbols, it just builds ASTs. We need to do that and to do that we need also to examine Jar files and binary components. I should have some initial Java code somewhere to be used as an initial inspiration. Fun times are ahead...

Adding tests against multiple usages of conflicting options

As a follow up of #30

Command not implemented in interactive mode closes program

In the interactive mode, ff the user tries to execute a command that is not implemented, he gets an error such as: Command not implemented: , and the program closes.

I think that it would be more natural to show the error and continue the execution.

Testing withModifiers protocol

Does it work for SingleFieldDeclaration?
Does it work for MethodDeclaration?
Does it work for TypeDeclaration?
Does it work for FieldDeclaration?

Item 11: Cloneable, not use the constructor in not final classes

It is wrong to use the constructor in the clone method of not-final classes

Item24: Suppress warning about generics

Avoid any warning to be produced.

Do not suppress Warning on entire classes.

Score classes according to their smells

As suggested here (http://tomassetti.me/effective-java-a-tool-to-explore-and-measure-your-java-code-written-in-clojure/#comment-3321) we could assign a score to classes to help find out which classes should be examined first in an unknown codebase

Item 9: verify equals and hashCode are overridden together

Are there acceptable exceptions?

Configure CI integration

Start with Travis, it should be enough for now.

Provide example and documentation for interactive mode

...maybe a screencast?

Testing withPackageName protocol

Should we fear to have null parent somewhere along the line?

Adding multimethod for determing alignment

Integer should be aligned to right, class qnames to left

Item 16: limit inheritance warning on extension in another package

We should prefer composition

Issue 17

Constructors of non final classes should not invoke overridable methods

Adding space between columns

Catch cli errors

For example running "lein run -l -q" should be an error

Release first version on Clojars

And explain how to use it in the Readme.

What should we do to make it usable from Maven?

Use clojure idiomatic names for functions

I think names should be separated by hyphens instead of using camel-case, so:

foo-bar ; good
fooBar ; bad

Item 11: Cloneable

Clone should return the same class of the defining class and do not declare to throw CloneNotSUpportedException.

They should also not call not-final methods.

Unable to run standalone 0.1.2-snapshot on windows

So, downloaded the 01.2-SNAPSHOT.jar file. Trying to run it on Windows 7 with java 8:

$ java -version
java version "1.8.0_31"
Java(TM) SE Runtime Environment (build 1.8.0_31-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.31-b07, mixed mode)

Both from bash and from the cmd prompt, I get a null pointer exception:

C:\Users\dan.moore\project\effectivejava>java -jar effectivejava-0.1.2-SNAPSHOT-standalone.jar
Exception in thread "main" java.lang.ExceptionInInitializerError
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:344)
        at clojure.lang.RT.loadClassForName(RT.java:2093)
        at clojure.lang.RT.load(RT.java:430)
        at clojure.lang.RT.load(RT.java:411)
        at clojure.core$load$fn__5066.invoke(core.clj:5641)
        at clojure.core$load.doInvoke(core.clj:5640)
        at clojure.lang.RestFn.invoke(RestFn.java:408)
        at app.core__init.load(Unknown Source)
        at app.core__init.<clinit>(Unknown Source)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:344)
        at clojure.lang.RT.loadClassForName(RT.java:2093)
        at clojure.lang.RT.load(RT.java:430)
        at clojure.lang.RT.load(RT.java:411)
        at clojure.core$load$fn__5066.invoke(core.clj:5641)
        at clojure.core$load.doInvoke(core.clj:5640)
        at clojure.lang.RestFn.invoke(RestFn.java:408)
        at clojure.lang.Var.invoke(Var.java:379)
        at app.core.<clinit>(Unknown Source)
Caused by: java.lang.NullPointerException
        at app.javaparser__init.load(Unknown Source)
        at app.javaparser__init.<clinit>(Unknown Source)
        ... 20 more

I get a similar error when running it in lint mode.

Organize namespaces

Probably app is a very bad name for the namespace. We should rename all of them and then we could use import-vars from https://github.com/ztellman/potemkin to import and re-export the symbols defined in the namespace. For example we could have one namespace name app.model.facade which expose all the content of all the namespaces with name app.model.*

SolveSuperclass

Given this example:

class B extends A {
}

class C extends B {
}

We need to find the superclasses of C (A and B).

We have most of the logic in place for that, but I could write the last bit for this particular case.

I would write a function named "solveSuperclass" in funcs.clj which would get a ClassDeclaration instance and basically call

(solveClass  classDeclaration nil (.getSuperclass classDeclaration)

solveClass is a method from a protocol.

Once we have this function we can create getAllSuperclasses calling recursively solveSuperclass.

Java linter modality in combination with svn diff / git diff

Ideally I would know which errors/warnings refer to the lines/classes I am changing, so I would like to somehow pipe it with svn diff or git diff.

While it could be easy to assign each warning to a class, it could be trickier to assign specific lines.

I should think about that.

mcp query fails when no threshold is specified

When I execute lein run -- --query mcp the program raises a NullPointerException.
It does not happen if I specify a threshold: lein run -- --query mcp -t 1, but raises the same kind of exception if the threshold is <= 0.

Add Item 10 checks to query and interactive modes

Capital case names should be used for final static fields

And those fields should be note arrays (which are mutable)

Item 7: finalizers

We could recognize classes which has finalizers. This one should be easy.

Improve code quality using kibit

Run kibit and use suggestions to improve quality

Modify License setting the copyright info

Fill information in this line Copyright {yyyy} {name of copyright owner} in License

Move to JavaParser 2.1.1

Help message in interactive mode does not mention the load operation

ConstructorDeclaration QName should list also parameters

To distinguish among constructors of the same class.
Same applies to MethodDeclaration.

It should be fixed in javaparser.clj, around line 70

In the help of the interactive mode the command "load" is not listed

When in interactive mode the help command produce this output:

h/help                      : print this help message
q/quit/exit                 : close the shell
list                        : list classes loaded
mc/many-constructors th NUM : list classes with NUM or more constructors

it should also include the load command

Increase code coverage

Running lein cloverage I get this:

Produced output in /home/federico/repos/effectivejava/target/coverage .
HTML: file:///home/federico/repos/effectivejava/target/coverage/index.html

|                         :name | :forms_percent | :lines_percent |
|-------------------------------+----------------+----------------|
|                       app.cli |        63.27 % |        33.33 % |
|                      app.core |        12.45 % |        27.12 % |
|               app.interactive |        10.39 % |        21.79 % |
|          app.itemsOnLifecycle |        72.66 % |        81.37 % |
|                app.jarloading |        97.20 % |        96.88 % |
|     app.javaparser.navigation |        63.34 % |        94.12 % |
|        app.javaparser.parsing |        98.68 % |       100.00 % |
|                    app.linter |        17.44 % |        45.83 % |
|          app.model.javaparser |        61.66 % |        78.17 % |
|           app.model.javassist |        90.91 % |        66.67 % |
|                app.operations |        60.80 % |        82.14 % |
|       app.symbol_solver.scope |        97.85 % |        98.89 % |
| app.symbol_solver.type_solver |        90.91 % |       100.00 % |
|                     app.utils |        92.96 % |        94.44 % |
Files with 100% coverage: 2

Forms covered: 59.73 %
Lines covered: 75.79 %

We should first of all organize better the tests (especially w.r.t the new modules for symbol resolution) and then focus on improving code coverage where possible. I would try to track progress in this issue.

Implement Item 4

We want to recognize Utils classes. We could use the name and/or look for classes which has only static methods and fields (and at least one method)

'list' operation does not work as expected in interactive mode

After loading some classes, running 'list' shows the loaded classes, but it also shows this error: 'No classes loaded. Use < load > first' and exits the program.

Convert all the queries to use the operation record

Convert also the cli and repl to take advantage of the names and shortcuts of queries

Item 10: provide access to all fields used in ToString

Otherwise force programmer to call toString

Need to shorten constructors and methods when printed in table

maybe we can shorten package to one letter (when non ambiguos) or remove the common prefix of packages. We could also avoid printing the parameters of generics maybe

Inconsistency: directory required in query mode but not in linter mode.

When using the linter mode, if the user does not specify a directory, the program uses the current one. On the other hand, when using the query mode, the program raises an error if the user does not specify a directory.

Confusing behavior enter key in interactive mode

When in the interactive mode, if the user presses the enter key, he will get an error like this:

ERROR: Parse error at line 1, column 1:
nil
^
Expected one of:
singletons (followed by end-of-string)
st (followed by end-of-string)
finalizers (followed by end-of-string)
f (followed by end-of-string)
list (followed by end-of-string)
q (followed by end-of-string)
quit (followed by end-of-string)
exit (followed by end-of-string)
h (followed by end-of-string)
help (followed by end-of-string)
many-costructor-params
mcp
many-constructors
mc
load

Wouldn't it be more intuitive to get something like this when pressing enter multiple times?

If you think so, I can fix this.

Item 8: float and double fields

In the equals method float and double fields should be compared using Float.compare and Double.compare because of the existence of NaN and -0.0f (see Float documentation).

We could write a query that check that.

Threshold for mc query is ignored in interactive mode

The threshold seems to be set to 5 ignoring the user input.
For example, using the examples classes included in the project:

mc th 7

class | numberOfConstructors

japa.parser.ast.body.BaseParameter | 5
japa.parser.ast.body.FieldDeclaration | 5
japa.parser.ast.body.MethodDeclaration | 5
japa.parser.ast.expr.ArrayCreationExpr | 5
org.springframework.jdbc.core.ResultSetSupportingSqlParameter | 6
org.springframework.jdbc.core.SqlInOutParameter | 7
org.springframework.jdbc.core.SqlOutParameter | 7
org.springframework.jdbc.core.SqlParameter | 7
org.springframework.jdbc.core.support.SqlLobValue | 8

Item 8: in the equals method an instanceOf should be present and should not target other classes

• .getClass should not be used
• instanceOf should be used
• the null comparison before the instanceOf is useless

Name collision warning

I get this warning while executing the program:

WARNING: Named already refers to: interface clojure.lang.Named in namespace: app.model.javaparser, being replaced by: #'app.model.protocols/Named

Command to filter only one package in interactive mode

Maybe for certain commands I want to consider only one package

Maven plugin

Please create a Maven wrapper plugin so that this tool can be used easily in automated builds