使用tomcat执行Web应用程序

Question

I have started using tomcat 7 for few days. I have tried executing many JAVA BASED web application with it. I actually want to check the flow of the java based web applications. That means in which sequence the methods of web application get executed. To do this I profile tomcat server with java profiler.

My profiler works like this:

1. I deploy war file of an application into web Apps dir of tomcat.
2. I start the server by ./startup.sh
3. I access the application in browser and execute it.
4. I stop the server by ./shutdown.sh .

and after I stop the server, the profiler dumps the output in xml format(it shows heirarchy of methods as calling context tree).(MY profiler basically profiles methods of java classes.)

As you know, may be because Tomcat is based on servlet, for 2 exactly same runs of an application(I follow above 4 steps 2 times and have 2 different output for 2 same runs), profiler gives different outputs. Q.1) I dont exactly know why this happens would be very curious to know the reason behind it.

Also the output is very large (around 200 MB) even for simple application. To limit the size of the output and to have same outputs for 2 exactly same runs, I have excluded methods of org.apache.* from profiling. Because I am ultimately interested in knowing the flow of the web application itself.(to know in which sequence methods of web application get executed). For this scenario I have following questions.

Q.2) Running application by deploying war file and running it by fetching it form the directory itself can make difference in the output of the profiler ? or can it affect a sequence of methods in which they execute in both the cases ?

Q.3) I would like to know what happens when I execute jsp page of an application ? I mean how does tomcat execute them? step wise please....

Q.4) when I check the output of the profiler after executing an application, I see large no of methods from org/eclipse/jdt/internal/... get executed. So what do this classes do actually ? Why do I have them in my output ?

Please let me know if I have failed to explain my questions. I kiind of searched a lot but could not find very precise answers to my questions.

I would really appreciate your responses..

Thanks you.

Answer 1

I strongly recommend to read a bit about tomcat works. In short

Q.2 Shouldn't make any difference.

Q.3 JSPs are compiled to servlet classes when they get called. If there is no Servlet class for the JSP tomcat makes one. If there is a corresponding servlet class, tomcat looks which one is younger, the JSP or the servlet. If the JSP is younger it does a new compilation, if not it uses the servlet.

Q.1 Not sure. Could be a multithreading/timing thing, Maybe it's the way your profiler works.

Q.4 Not sure. Could a be classes from the profiler or libraries used by your servlet code?

EDIT : For Q.4 look at Ian Roberts' comment to the question.

What profiler do you use? How about going stepwise through the code by debugging it?