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Forces compiler to trigger custom warnings when @WTFs are used. Includes custom jUnit runner that scans for @WTFs across project and generates metrics

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Amount of WTFs per Project

This library is a by-product that derived from what I was doing few days ago:

I was dabbling with Java and decided to take a break. I came across a well know image that depicts code review session behind closed doors. The image called "The only valid measurement of code quality: WTF/minute". I decided to make an extension to the latter concept.

This library brings you the ability to mark code smells in your source code (Classes, methods, fields etc.) with 'WTF' annotation. The WTF annotation accepts an arbitary message, if none provided, the default message 'Dude.. WTF?!' is used instead. When source compiles, the compiler generates a warning using the message from detected annotation(s) and information about marked element type. The following is a sample output from compiling a class containing WTF annotations:

Warning: : In CLASS [wtf.per.project.model.DummyPojoImpl] :
CLASS level => WTF?! Are you for real?! This naming convention is bad!
Warning: : In CLASS [wtf.per.project.model.DummyPojoImpl] :
FIELD 'SOME_CONSTANT' => WTF?! What is this non-descriptive name?
Warning: : In CLASS [wtf.per.project.model.DummyPojoImpl] :
CONSTRUCTOR 'DummyPojoImpl(java.lang.String)' => WTF?! Dude.. WTF?!

The library also provides a custom JUnit test runner class. The runner consumes package name, annotation class and search filter through @Grep annotation (used in conjunction with @RunWith). The runner scans .class files under the given package, its sub-packages and JARs for the given annotation (for example WTF.class) occurances. If String regex pattern provided in @Grep, classes are filtered out from being scanned based on the filter. The runner uses a test class internally to assert whether the code is still infested with WTFs (or any other annotation class set in @Grep).

The scanning of .class files within given package, its sub-packages and any JAR files found, is done using byte code analysis instead of reflection. In other words, the scanning is done without loading classes into JVM PermGen Space and wasting resources.

So, if runner's test assertion fails (given annotation like @WTF found present in the code), the test class generates metrics about how many WTFs are there and where. These metrics appended to the assertion failure message. For example, the following is the example of the custom JUnit runner:

@Grep(packageName = "wtf.per.project.model", classNameFilter = ".*", annotationClass = WTF.class)
public final class WTFsPerProjectRunner {


I have few POJOs marked with WTF annoation, so the following is the produced output after running the above class:


Dude.. WTF!? Sources in package [wtf.per.project.model] are infested with [19] WTFs:

[ANNOTATION] interface wtf.per.project.model.SomeAnnotation
[CLASS] class wtf.per.project.model.DummyPojoImpl
[CONSTRUCTOR] private wtf.per.project.model.DummyPojoImpl(java.lang.Integer,java.lang.String)
[CONSTRUCTOR] public wtf.per.project.model.DummyPojoChild(java.lang.String)
[CONSTRUCTOR_PARAMETER] #2 private wtf.per.project.model.DummyPojoImpl(java.lang.Integer,java.lang.String)
[ENUM] class wtf.per.project.model.DummyPojoImpl$Names
[ENUM] class wtf.per.project.model.Surnames
[FIELD] private java.lang.String
[FIELD] private static final java.lang.String wtf.per.project.model.DummyPojoImpl.SOME_CONSTANT
[FIELD] public static final wtf.per.project.model.Surnames wtf.per.project.model.Surnames.JOHNSON
[INTERFACE] interface wtf.per.project.model.DummyPojo
[INTERFACE] interface wtf.per.project.model.submodel.DummySubmodelPojo
[LOCAL_CLASS] class wtf.per.project.model.DummyPojoChild$1SomeLocalClass
[MEMBER_CLASS] class wtf.per.project.model.DummyPojoChild$SomeMemberClass
[METHOD] private static void wtf.per.project.model.DummyPojoChild.thisIsPrivateStaticMethod()
[METHOD] private void wtf.per.project.model.DummyPojoImpl.somePrivateMethod()
[METHOD] public void wtf.per.project.model.DummyPojoImpl.setName(java.lang.String,java.lang.Integer)
[METHOD_PARAMETER] #1 public void wtf.per.project.model.DummyPojoImpl.setName(java.lang.String,java.lang.Integer)
[METHOD_PARAMETER] #2 public void wtf.per.project.model.DummyPojoImpl.setName(java.lang.String,java.lang.Integer)

expected:<0> but was:<19>

Another example of the custom JUnit runner:

//Grep only inner classes                                                                           
    @Grep(packageName = "wtf.per.project.model", classNameFilter = ".*[$].*", annotationClass = WTF.class)               
    public final class WTFsPerProjectRunner {                                                                       




Dude.. WTF!? Sources in package [wtf.per.project.model] are infested with [3] WTFs:

[ENUM] class wtf.per.project.model.DummyPojoImpl$Names
[LOCAL_CLASS] class wtf.per.project.model.DummyPojoChild$1SomeLocalClass
[MEMBER_CLASS] class wtf.per.project.model.DummyPojoChild$SomeMemberClass

expected:<0> but was:<3>


I created this library for fun. Nothing more. If someone actually decides to use it - great.


  • None


  • Java 1.6 (or higher). This will not run on 1.5 or lesser.


In my implementation I am using a service provider implementation which is identified by placing a provider-configuration file in the resource directory META-INF/services. With JSR 269, annotation processors are discovered by searching the classpath for the latter file (META-INF/services/javax.annotation.processing.Processor). The contents of this file enumerate available annotation processors (in other words this file is a provider-configuration file).

If you try to compile the code using Maven, most probably you are going to get the following error:

Bad service configuration file, or exception thrown while constructing Processor object: 
javax.annotation.processing.Processor: Provider wtf.per.project.annotation.processing.WTFProcessor 
not found

RESOLUTION Apperantly Maven has a bug. The following resource talks about workaround to the problem when Maven cannot find annotation processor:

The workaround is to modify the maven build lifecycle to compile the project in two passes. The first pass compiles just the annotation processors (with annotation processing disabled), the second compiles the rest of the project (with annotation processing enabled). The first pass makes the compiled annotation processors available for the second pass. Check my POM file.

How to add support into your application

Just add the wtf-per-project-x.x.jar to your classpath and start annotating your source code away.


Sure. Let me know if you have any problems or you discovered some bugs.

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