How to log/trace any method call of object in java

I need some thing like a Python decorator. I need to store some information, specifically the method called, its start time, its end time, and its arguments. I开发者_JS百科 cannot import anything outside of Java 1.5 libraries. Is there some thing like what is available in Python?

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Good tracing tool for Java is BTrace.

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You can try some profiler using Java Management Extensions or java agent.

See http://java.sun.com/developer/technicalArticles/releases/j2se15/#mnm

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Java Instrumentation?

http://download.oracle.com/javase/6/docs/api/java/lang/instrument/Instrumentation.html

Example:

http://today.java.net/pub/a/today/2008/04/24/add-logging-at-class-load-time-with-instrumentation.html

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No, Python decorators do not let you monitor all the code without changing anything. You still have to put your decorator everywhere (and - essentially - wrap each of your functions into a function that does the counting).

I am not sure if I understand your requirements (you do not say if you need the code for production or testing; also, the requirement "not to import anything" is bizarre: are all your classes in the default package? are you allowed to use an IDE and a compiler?), but I think the simplest way would be to use Javassist (the second link kindly provided by cschooley is a perfect introduction), but do not use the agent: instead use CtClass#write() to instrument class files and save them to disk (possibly in a custom ant task). This way the final build will not need any special set-up.

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You might get away with a Java Proxy class if you can rely on interface methods only.

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@Loggable annotation and an AspectJ aspect from jcabi-aspects may help you. Annotate all your methods and every time they are being called SLF4J will receive log messages:

@Loggable(Loggable.DEBUG)
public String load(URL url) {
  return url.openConnection().getContent();
}

In the next versions of jcabi-aspects a full logging of a class will be implemented: https://github.com/yegor256/jcabi/issues/129