Question

I’m trying to optimize the startup time/class loading time of my Java web app because its on the Google App Engine and startup time is important.

Is there a way I can turn on some sort of class loading debug messages or someway to see where time is being spent while class loading? I want to see if any specific libraries take a while to load and then get rid of them if they aren’t essential.

Answer 1

If you want to see what classes were loaded and in what order you can run with the -verbose flag.

Example:

java -verbose:class <MyProgram>

Output:

[Loaded java.lang.Object from shared objects file]
[Loaded java.io.Serializable from shared objects file]
[Loaded java.lang.Comparable from shared objects file]
[Loaded java.lang.CharSequence from shared objects file]
[Loaded java.lang.String from shared objects file]
[Loaded java.lang.reflect.GenericDeclaration from shared objects file]
[Loaded java.lang.reflect.Type from shared objects file]
[Loaded java.lang.reflect.AnnotatedElement from shared objects file]
[Loaded java.lang.Class from shared objects file]
[Loaded java.lang.Cloneable from shared objects file]
[Loaded java.lang.ClassLoader from shared objects file]
[Loaded java.lang.System from shared objects file]
[Loaded java.lang.Throwable from shared objects file]
[Loaded java.lang.Error from shared objects file]
..
..
..