I have app which folowing by archunit rules and I get:
NO_CLASSES_SHOULD_ACCESS_STANDARD_STREAMS
failed rule - it's mean I can't use standard Java I/O Streams. But what I can use instead?
How I can avoid this architecture rule with another Java methods instead standard streams? Because My arch rules are failing
NO_CLASSES_SHOULD_ACCESS_STANDARD_STREAMS - is, the System.out, System.err, and printStackTrace methods: use a logging library instead. So I think you need remove all println System.out.println()
The documentation, i.e. the javadoc of NO_CLASSES_SHOULD_ACCESS_STANDARD_STREAMS, says:
It is generally good practice to use correct logging instead of writing to the console.
Writing to the console cannot be configured in production
Writing to the console is synchronized and can lead to bottle necks
For information about checking this rule, refer to GeneralCodingRules.
You asked how to avoid this architecture rule. Just do what it says: Use logging!
Related
I'm trying to understand if is possible to configure AssertJ to log the negative result of an assertion to a file without interrupting the routing that is running the comparison.
The reason behind this request is that we are comparing the JSON generated by two version of a software to spot differences, but instead of manually creating all the checks I would like to leverage the functionalities already available in AssertJ.
As a possible solution to this I was thinking of using a try/catch for assertion exceptions, but I'm really concerned about the overall performance of the routine.
Any idea?
You can access the error message by catching the AssertionError, then use whatever logging framework.
If you want to capture all the errors (and not fail at the first one), use soft assertions.
If we spoke about any logging frameworks:
we can use File LoggingAppender
set log level for ERROR or WARN
define TestClass or Pacakge for reduce unnecessary messages
I need to diagnose all invoked methods in a class(either declared in the class or not) using it's source code. Means that give the class source code to a method as an input and get the invoked method by the class as the output. In fact I need a class/method which operates same as java lexical analyzer .
Is there any method to diagnose all invoked methods ?
of course I tried to use Runtime.traceMethodCalls(); to solve the problem but there was no output. I've read I need to run java debug with java -g but unfortunately when I try to run java -g it makes error. Now what should I do ? Is there any approach ?
1) In the general case, no. Reflection will always allow the code to make method calls that you won't be able to analyze without actually running the code.
2) Tracing the method calls won't give you the full picture either, since a method is not in any way guaranteed (or even likely) to make all the calls it can every time you call it.
Your best bet is some kind of "best effort" code analysis. You may want to try enlisting the compiler's help with that. For example, compile the code and analyze the generated class file for all emitted external symbols. It won't guarantee catching every call (see #1), but it will get you close in most cases.
You can utilize one of the open source static analyzers for Java as a starting point. Checkstyle allows you to build your own modules. Soot has a pretty flexible API and a good example of call analysis. FindBugs might also allow you too write a custom module. AFAIK all three are embeddable in the form of a JAR, so you can incorporate whatever you come up with into your own custom program.
From your question it is hard to determine what is exactly problem you're trying to solve.
But in case:
If you want to analyze source code, to see which parts of it are redundant and may be removed, then you could use some IDE (Eclipse, IntelliJ IDEA Community Edition etc.) In IDE's you have features to search for usages of method and also you have functionality to analyze code and highlight unused methods as warnings/errors.
If you want to see where during runtime some method is called, then you could use profiling tool to collect information on those method invocations. Depending on tool you could see also from where those methods were called. But bare in mind, that when you execute program, then it is not guaranteed that your interesting method is called from every possible place.
if you are developing an automated tool for displaying calling graphs of methods. Then you need to parse source and start working with code entities. One way would be to implement your own compiler and go on from there. But easier way would be to reuse opensourced parser/compiler/analyzer and build your tool around it.
I've used IntelliJ IDEA CE that has such functionalitys and may be downloaded with source http://www.jetbrains.org/display/IJOS/Home
Also there is well known product Eclipse that has its sources available.
Both of these products have enormous code base, so isolating interesting part would be difficult. But it would still be easier than writing your own java compiler and werifying that it works for every corner case.
For analyzing the bytecode as mentioned above you could take a look at JBoss Bytecode. It is more for testing but may also be helpful for analyzing code.
sven.malvik.de
You may plug into the compiler.
Have a look the source of Project Lombok for instance.
There is no general mechanism, so they have one mechanism for javac and one for eclipse's compiler.
http://projectlombok.org/
The program I'm building seems to freeze at some points on the user's system. When I test the very same steps, I see no problem. Even though Java is supposed to be a platform-independent VM, my guess is it has to do with the systems we're using (I'm on linux, the user on Mac), maybe something with file access.
I cannot access the user's system, and the user has no idea what debugging means. In order to test where the problem is, I was thinking of writing the program's progress to a file, and having him send me the file when there's a problem. Therefore my question:
Is there some kind of library which allows writing the line by line execution of a program to a file? Ideally, the values of certain variables would also be included.
edit: I'm familiar with Logger, but (like one answer says), that would require writing a lot of log statements. Is there some way to do this automatic? Maybe line by line is overkill, but something like log each method entry/exit would definitely work.
Thanks a lot!
This might be a good use case for aspect-oriented programming. Specifically, the AspectJ library for Java might suit your needs (there are others, but this is the one I'm most familiar with). You could define a logging aspect that would automatically insert method entry/exit log messages into the methods you wish to trace, without having to modify the code for those methods. The aspect can be included or excluded as you wish whenever you build the application (eg, include it just for this user until you resolve the issue).
Something like the following might be a good start:
aspect LogAllMethods {
Log log = new Log(); // pseudocode -- replace with whatever logging mechanism you like
before(): call(public * com.mycompany.*.*(..)) {
log.log("Entered method: " + thisJoinPoint);
}
after(): call(public * com.mycomapny.*.*(..)) {
log.log("Leaving method: " + thisJoinPoint);
}
}
This basically says that, before and after any public method call in the package com.mycompany, log the entry/exit and the name of the method (thisJoinPoint is a special variable in AspectJ that refers to the point in the program's execution that the aspect is being applied to). The AspectJ documentation has some nice tutorials and examples of defining aspects and how they can be used, as well as instructions on how to introduce aspects into your application.
This might be overkill for your situation and underutilization of AspectJ, but it should allow you to do some fine-grained debugging without having to add logging calls to every method in your code.
Typically the debug information you want would be included in a log file. Logging frameworks like Java's built in Logging API allow you to configure what severity of messages to produce when the program is run. In other words, you could have it normally report severe errors only, but enable debug output selectively when you need more information.
However, logging frameworks normally require you, the programmer, to explicitly tell it what to log. It doesn't simply log everything (that would be a lot of data too!).
It sounds like what you want is logging in your application. See the Wikipedia article for Java Logging Frameworks for details.
Some of the more common logging frameworks, all mentioned in the aforementioned article, are:
Log4J
Java Logging API
Apache Commons Logging
SLF4J
I want to log information to a file and want to know is there any advantage in using the Java Logger class versus my own personal method of logging?
I know using a logger I just add my own FileHandler to the logger. My personal method is just using a FileOutputStream.
Honestly your logger may be as good, it's pretty easy to put in log levels, filtering, etc.
The problem is when you start to put together code from 10 different groups each with their own logging. Some use System.out, some use some custom logger, some use log4j, ...
How do you parse or redirect the output? How do you filter all that output to just show your messages (For instance, filtering options in log4j won't prevent messages being sent straight to System.out).
It's a pretty big bulk change depending on which system you are moving from/to. Better just to use one very common one from the beginning and hope that it's the one everybody else on the project chooses.
The real question is: why would you bother writing your own logger when there are already existing libraries for doing that? Does your logger do something that the others don't? I kind of doubt it.
Standardization is another big issue - see Bill K's answer.
For most scenarios, a standard logging framework is the way to go. They are pretty flexible. But using your own implementation can also be a valid option, specially if we are not speaking of traditional logging (global debugging, problems, warning messages) but about specific informational meesages or accounting.
Among other factors, bear in mind that the standarization of logging allows third party libraries to cooperate. For example, if you have a standard web application using (say) Hibernate, and you have configured a standard Java logging lib, then you can not only log from your own code but also tell Hibernate to log debugging info to your log files (not necessarily the same files). That is very useful - almost a must.
If you code your own logging library with a plain FileOutputStream, you must decide -among other things- if you are going to keep the file opened, or reopen-append-close in each write - and you must take of synchronization and related issues. Nothing terribly complicated, though.
The logger gives to ability to define different levels of importance of the logged messages and the ability to use different sink for the output - the console, a file, etc.
Also it's easy to enable or disable only some type of message when using a logger - for example you don't want to see every debug message in production.
A logging framework allows you specify logging levels (e.g. log only critical messages, log only debug messages etc.). It also allows you to log to multiple destinations (e.g. to a file, to syslog etc.) and you can do this even after your application is fully built by just changing a config file and not changing any code. It can also format your logs easily depending on various parameters.
There are numerous other advantages since proper logging is a rather involved problem and these packages have been written to solve them. I think the important question, why would you not use them?
Well I would always prefer tested thing and approved by community over something which still need a lot of test. Logger allows you many things which will consume you some time to implement and to test the robustness of your solution. A big plus will be the know-how of the next person who will do something with your code, in case it will be your logger, normally it would take more time to learn how its working out, since there is much more examples and documentation for java.util.logger.
Like all others mention, there are more advantages to using a more common logging system over writing your own. To be honest, the Java util logging api is not nearly as extensive and configurable as other libraries you might find out there on the internet.
Bare in mind that rolling your own always has the disadvantage of being less tested and therefore more prone to break or skip some potentially crucial messages.
Personally I prefer using SLF4J since it allows me to plug in adapters for more commonly used logging frameworks and then let's me pick my own actual logging implementation, this solves most of the problems with different library writers preferring different logging frameworks. And if you consider yourself up for the task you could writer an implementation for SLF4J yourself ;)
Have you heard of any library which would allow me to set up tracing for specific methods at runtime?
Instead of adding (and removing) lots of System.out.println in my code (and having to re-compile and re-deploy) I would like to have a magic thing which would print out a line for each call of selected method without any change in the code. This would work without re-compiling, so some kind of JVM agent (or some non-standard JVM would be needed?). Sounds like a job for aspect programming?
A typical scenario would be to start an application, configure the traced methods dynamically (in a separate file or similar) and then everytime a selected method is called a line with its name (and arguments) is printed out to System.out (or some log file).
Naturally one could think of tens of additional features, but this basic set would be a great tool. BTW, I use Eclipse interactive debugger too, not only the System.out tracing technique, but both have some advantages and sometimes Eclipse is not enough.
Yes what you are referring to is known as Aspect oriented programming. A typical library providing this for Java is AspectJ. You define what are called pointcuts, essentially regular expressions for classes and method names, including wildcards, and the code to execute at each pointcut, known as an advice. This is useful for logging and also security checks and similar cross cutting concerns.
You can turn pointcut advices on and off through configuration. You can have an advice execute before a method call, after it returns or even after it throws an exception. Arguments are also available.
An aspectj java agent is needed for this to work.
In my experience, that kind of very detailed tracing (much more detailed than one would normally use for logging) as a debugging technique is indicative of insufficient unit testing and integration testing.
You can do this using a tool called InTrace.
NOTE: InTrace is a free and open source tool which I have written.
Log4J useful for disabling logging depending on "log-level" (DEBUG, INFO, WARN, FATAL).
You specify in configuration file what the least level you want to appear in logs, e.g., don't log anything below INFO level, and voila!
Looks like there's yet another solution - called Byteman. In their own words:
Byteman is a tool which simplifies tracing and testing of Java
programs. Byteman allows you to insert extra Java code into your
application, either as it is loaded during JVM startup or even after
it has already started running. The injected code is allowed to access
any of your data and call any application methods, including where
they are private. You can inject code almost anywhere you want and
there is no need to prepare the original source code in advance nor do
you have to recompile, repackage or redeploy your application. In fact
you can remove injected code and reinstall different code while the
application continues to execute.
Jackplay is the tool you are looking for.
It allows you to enable logging on method entry and exit points without any coding or redeployment.
It also allows redefining a method body. It gives you web based UI as control panel to enable or undo tracing on your class.methods.