I'm working on a project where we need to compile groovy classes at runtime and then instantiate objects from these classes and execute methods on it. The source for these classes exists as a string only in live environments.
These classes can contain pretty complex code, so there is a good chance of bugs hiding in there.
The problem with our approach is, that when we notice missbehavior in these classes, we can't use a comfortable method of debugging.
We can of course write and execute tests against these classes, but often times you just want to know what's going on step-by-step.
So my question is: Is there is a way to debug runtime generated groovy/Java classes?
The steps we currently take to track down bugs:
1) Write tests to reproduce the behavior
2) Read through the code. (obviously has a super bad success rate in complex classes)
3) Do instrumentation. We call a static "_break" method which we have written in a utils class (so no runtime generated stuff). In that _break method we can add a breakpoint. So this is almost as if we were debugging the runtime generated classes directly. The Problem with that approach is, that you have to recompile and add a new version of the groovy classes to the testsystem everytime you want to add/remove a _break call.
If you're wondering how we can even write tests for these classes, here is how:
For unit tests we copy the code from the strings into regular groovy classes. These are used for development and unit testing, because it gives us code completion and a fast way to at least execute the classes against simple tests.
We can debug the code on unit test level. The problem here is, that the data setup is too complex to reproduce certain combinations in unit tests.
For integration tests, we do the whole compilation, adding, executing process, just like it would happen in the live system.
We use Intellij 2017 as IDE and I currently have no idea if or how we could "connect" the bytecode to either the strings which is was generated from, or the copied groovy classes we use for unit testing.
Any other tool that would allow us to debug would be fine as well.
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What tools do you use to find unused/dead code in large java projects? Our product has been in development for some years, and it is getting very hard to manually detect code that is no longer in use. We do however try to delete as much unused code as possible.
Suggestions for general strategies/techniques (other than specific tools) are also appreciated.
Edit: Note that we already use code coverage tools (Clover, IntelliJ), but these are of little help. Dead code still has unit tests, and shows up as covered. I guess an ideal tool would identify clusters of code which have very little other code depending on it, allowing for docues manual inspection.
An Eclipse plugin that works reasonably well is Unused Code Detector.
It processes an entire project, or a specific file and shows various unused/dead code methods, as well as suggesting visibility changes (i.e. a public method that could be protected or private).
CodePro was recently released by Google with the Eclipse project. It is free and highly effective. The plugin has a 'Find Dead Code' feature with one/many entry point(s). Works pretty well.
I would instrument the running system to keep logs of code usage, and then start inspecting code that is not used for months or years.
For example if you are interested in unused classes, all classes could be instrumented to log when instances are created. And then a small script could compare these logs against the complete list of classes to find unused classes.
Of course, if you go at the method level you should keep performance in mind. For example, the methods could only log their first use. I dont know how this is best done in Java. We have done this in Smalltalk, which is a dynamic language and thus allows for code modification at runtime. We instrument all methods with a logging call and uninstall the logging code after a method has been logged for the first time, thus after some time no more performance penalties occur. Maybe a similar thing can be done in Java with static boolean flags...
I'm suprised ProGuard hasn't been mentioned here. It's one of the most mature products around.
ProGuard is a free Java class file shrinker, optimizer, obfuscator,
and preverifier. It detects and removes unused classes, fields,
methods, and attributes. It optimizes bytecode and removes unused
instructions. It renames the remaining classes, fields, and methods
using short meaningless names. Finally, it preverifies the processed
code for Java 6 or for Java Micro Edition.
Some uses of ProGuard are:
Creating more compact code, for smaller code archives, faster transfer across networks, faster loading, and smaller memory
footprints.
Making programs and libraries harder to reverse-engineer.
Listing dead code, so it can be removed from the source code.
Retargeting and preverifying existing class files for Java 6 or higher, to take full advantage of their faster class loading.
Here example for list dead code: https://www.guardsquare.com/en/products/proguard/manual/examples#deadcode
One thing I've been known to do in Eclipse, on a single class, is change all of its methods to private and then see what complaints I get. For methods that are used, this will provoke errors, and I return them to the lowest access level I can. For methods that are unused, this will provoke warnings about unused methods, and those can then be deleted. And as a bonus, you often find some public methods that can and should be made private.
But it's very manual.
Use a test coverage tool to instrument your codebase, then run the application itself, not the tests.
Emma and Eclemma will give you nice reports of what percentage of what classes are run for any given run of the code.
We've started to use Find Bugs to help identify some of the funk in our codebase's target-rich environment for refactorings. I would also consider Structure 101 to identify spots in your codebase's architecture that are too complicated, so you know where the real swamps are.
In theory, you can't deterministically find unused code. Theres a mathematical proof of this (well, this is a special case of a more general theorem). If you're curious, look up the Halting Problem.
This can manifest itself in Java code in many ways:
Loading classes based on user input, config files, database entries, etc;
Loading external code;
Passing object trees to third party libraries;
etc.
That being said, I use IDEA IntelliJ as my IDE of choice and it has extensive analysis tools for findign dependencies between modules, unused methods, unused members, unused classes, etc. Its quite intelligent too like a private method that isn't called is tagged unused but a public method requires more extensive analysis.
In Eclipse Goto Windows > Preferences > Java > Compiler > Errors/Warnings
and change all of them to errors. Fix all the errors. This is the simplest way. The beauty is that this will allow you to clean up the code as you write.
Screenshot Eclipse Code :
IntelliJ has code analysis tools for detecting code which is unused. You should try making as many fields/methods/classes as non-public as possible and that will show up more unused methods/fields/classes
I would also try to locate duplicate code as a way of reducing code volume.
My last suggestion is try to find open source code which if used would make your code simpler.
The Structure101 slice perspective will give a list (and dependency graph) of any "orphans" or "orphan groups" of classes or packages that have no dependencies to or from the "main" cluster.
DCD is not a plugin for some IDE but can be run from ant or standalone. It looks like a static tool and it can do what PMD and FindBugs can't. I will try it.
P.S. As mentioned in a comment below, the Project lives now in GitHub.
There are tools which profile code and provide code coverage data. This lets you see (as code is run) how much of it is being called. You can get any of these tools to find out how much orphan code you have.
FindBugs is excellent for this sort of thing.
PMD (Project Mess Detector) is another tool that can be used.
However, neither can find public static methods that are unused in a workspace. If anyone knows of such a tool then please let me know.
User coverage tools, such as EMMA. But it's not static tool (i.e. it requires to actually run the application through regression testing, and through all possible error cases, which is, well, impossible :) )
Still, EMMA is very useful.
Code coverage tools, such as Emma, Cobertura, and Clover, will instrument your code and record which parts of it gets invoked by running a suite of tests. This is very useful, and should be an integral part of your development process. It will help you identify how well your test suite covers your code.
However, this is not the same as identifying real dead code. It only identifies code that is covered (or not covered) by tests. This can give you false positives (if your tests do not cover all scenarios) as well as false negatives (if your tests access code that is actually never used in a real world scenario).
I imagine the best way to really identify dead code would be to instrument your code with a coverage tool in a live running environment and to analyse code coverage over an extended period of time.
If you are runnning in a load balanced redundant environment (and if not, why not?) then I suppose it would make sense to only instrument one instance of your application and to configure your load balancer such that a random, but small, portion of your users run on your instrumented instance. If you do this over an extended period of time (to make sure that you have covered all real world usage scenarios - such seasonal variations), you should be able to see exactly which areas of your code are accessed under real world usage and which parts are really never accessed and hence dead code.
I have never personally seen this done, and do not know how the aforementioned tools can be used to instrument and analyse code that is not being invoked through a test suite - but I am sure they can be.
There is a Java project - Dead Code Detector (DCD). For source code it doesn't seem to work well, but for .jar file - it's really good. Plus you can filter by class and by method.
Netbeans here is a plugin for Netbeans dead code detector.
It would be better if it could link to and highlight the unused code. You can vote and comment here: Bug 181458 - Find unused public classes, methods, fields
Eclipse can show/highlight code that can't be reached. JUnit can show you code coverage, but you'd need some tests and have to decide if the relevant test is missing or the code is really unused.
I found Clover coverage tool which instruments code and highlights the code that is used and that is unused. Unlike Google CodePro Analytics, it also works for WebApplications (as per my experience and I may be incorrect about Google CodePro).
The only drawback that I noticed is that it does not takes Java interfaces into account.
I use Doxygen to develop a method call map to locate methods that are never called. On the graph you will find islands of method clusters without callers. This doesn't work for libraries since you need always start from some main entry point.
I am evaluating clover currently and wonder how to use it best. First I'd like to understand how it works conceptually.
1) What does instrumentation mean? Are the test-calls attached to implementation's statements?
2) How is this done? Are the tests actually executed with some fancy execution context (similar to JRebel e.g.) for this? Or is it more like static analysis ?
3) After a "clover-run", some DB is saved to disk, and based on this, reports are generated right? Is the DB-Format accessible? I mean Can I launch my own analysis on it, e.g. using my own reporting tools ? What information does the DB contain exactly? Can I see the mapping between test and implementation there ?
4) Are there other tools that find the mapping between test and implementation? Not just the numbers, but which test, actually covers a line of code ...
Thanks, Bastl.
How is this done? Are the tests actually executed with some fancy execution context (similar to JRebel e.g.) for this? Or is it more like static analysis?
During code instrumentation by Clover it detects which methods are test methods (by default it recognizes JUnit3/4 and TestNG). Such methods gets additional instrumentation instructions. Shortly speaking, entering a test method will usually instantiate a dedicated coverage recorder which measures coverage exclusively for this test. More information about per test recording strategies available in Clover:
https://confluence.atlassian.com/display/CLOVER/Clover+Performance+Results
https://confluence.atlassian.com/display/CLOVER/About+Distributed+Per-Test+Coverage
After a "clover-run", some DB is saved to disk, and based on this, reports are generated right?
A Clover database (clover.db) contains information about code structure (packages, files, classes, methods, statements, branches), it has also information about test methods. There are also separate coverage recording files (produced at runtime) containing information about number of "hits" of given code element. Clover supports both global coverage (i.e. for the whole run) as well as per-test coverage (i.e. coverage from a single test).
More information is here:
https://confluence.atlassian.com/display/CLOVER/Managing+the+Coverage+Database
Is the DB-Format accessible?
The API is still in development (https://jira.atlassian.com/browse/CLOV-1375), but there is a possibility to get basic information. See:
https://confluence.atlassian.com/display/CLOVER/Database+Structure
for more details about DB model and code samples.
But the question is: do you really need to manually read this DB? You wrote that:
Can I see the mapping between test and implementation there ?
Such mapping is already provided by Clover - in the HTML report for example if you click on a source line it will pop up a list of test methods hitting this line.
PS: I'm a Clover developer at Atlassian, feel free to contact me if you have any questions.
What does instrumentation mean?
Additional code is woven in with your code.
Are the test-calls attached to implementation's statements?
I am not sure what you mean but it could be instructions or call to methods. Trivial methods will be inlined by the JIT at runtime.
How is this done?
There are many ways to do it, but often the Instrumentation class is to used to capture when a class is being loaded and a library like Objectweb's ASM is used to manipulate the code.
Are the tests actually executed with some fancy execution context
The context counts which lines have been executed.
Or is it more like static analysis ?
No, it is based on what is called.
After a "clover-run", some DB is saved to disk, and based on this, reports are generated right? Is the DB-Format accessible?
You had best ask the producers of clover as to the content of their files.
Are there other tools that find the mapping between test and implementation? Not just the numbers, but which test, actually covers a line of code ...
There are many code coverage tools available including EMMA, JaCoCo, Cobertura, IDEA has one builtin.
Is there a program out there that can allow me to find all ignored junits?
By this I mean, I have seen unit tests that use the #Ignore and tests with method name like ignore_testFoo() or xtestBar() or xxtestBar1(), which all get ignored and they are very hard to find sometimes.
I could grep for those cases, but I was wondering if there was an application that would find any of those situations automatically.
I tried using cobertura to obtain coverage on junits, to see which methods were being executed and which were not being executed, and picking apart the bad unit tests that was.
I was just wondering if there was a program or another method to obtain this information without hacking something up.
A static analysis tool would serve you well here. Checkstyle is a decent choice amongst them, it has a long list of modules, and worst case you can easily write your own module to validate any coding convention you need.
You would locate or create a module for it then execute to find any non-conforming code.
Edit
PMD looks to be an excellent choice to handle this task. It actually comes with a set of JUnit rules already built in and its very easy to combine rules or create new ones.
It should be easy to detect ignored tests using junit3 by a grep on your java test files. Find all lines matching test and parenthesis but with a method name that doesn't start by test.
For junit4, you could
* implement your own test runner by extending the default one, print out ignored tests
* build a small app that loads test classes, get all declared methods through introspect, print out those markedas ignored.
There may be a tool to do that, maybe even some runners already do, but actually it could take a few hours to have those tools from scratch if you really need them.
I have some fairly complex java programs with lots of if/else statements where various components interact with each other. I have some test data which exercises the code as much as possible.
Is there a way for me to run my code against this data and get information about which code paths were and were not executed?
(by test files, I mean I literally have text based csv files with hundreds of thousands of lines. Think of these lines as a collection of parameters. I try to randomly generate these parameters to make sure all parts of my code are touched, but I'd like to be more sure since these programs have a high cost of failure)
I use EclEmma (Emma Eclipse plugin) with TestNG in Eclipse. It provides a nice visual indication of what is and isn't covered, plus coverage statistics in the coverage view.
I believe JUnit is supported, too.
I'm not sure about code paths, but for simple code coverage Emma is good. Has plugins for most of the major IDEs and "just works".
I think clover can do that
http://www.atlassian.com/software/clover/