debug jdk source can't watch variable what it is

源地址：http://stackoverflow.com/questions/18255474/debug-jdk-source-cant-watch-variable-what-it-is

Generally speaking, to be able to watch the variables while stepping through JDK source code, you need the class files to be compiled with debug information i.e. compile using

javac
-g

.

So your best bet is to either find an already compiled version with debug information (I couldn't find anything for JDK 7) or you can try compiling the source for yourself.

According to this post (please note that I haven't tried it) you don't need to compile all
sources, only the ones you need. Putting your newly compiled classes in the

$jdk/jre/lib/

ext/

endorsed

directory,
the new classes would be used instead the ones in the original

rt.jar

.

I believe that should get you started.

Update: Actually I have just tried this process and it is not hard at all. Tested on Windows, JDK 1.7.0_11. All the commands are invoked from command line:

Create your working folder. I chose

d:\

root
folder
Inside your working folder create the source folder i.e.

jdk7_src

and
output folder

jdk_debug

From your

JDK_HOME

folder
get the

src.zip

file
and unzip it inside

jdk7_src

Select what you will compile and delete the rest. For all of them you might need additional steps. I have chosen the folders:

java

javax

org

From your

JDK_HOME\jre\lib

get
the file

rt.jar

and
put in the work folder (this is only for convenience to not specify too large file names in the command line).
Execute the command:

dir
/B /S /X jdk7_src\*.java > filelist.txt

to create a file named

filelist.txt

with
the list of all java files that will be compiled. This will be given as input to

javac

Execute

javac

using
the command:

javac
-J-Xms16m -J-Xmx1024m -sourcepath d:\jdk7_src -cp d:\rt.jar -d d:\jdk_debug -g @filelist.txt >> log.txt 2>&1

This will compile all the files in the

jdk_debug

folder
and will generate a

log.txt

file
in your working folder. Check the log contents. You should get a bunch of warnings but no error.
Go inside the

jdk_debug

folder
and run the command:

jar
cf0 rt_debug.jar *

. This will generate your new runtime library with degug information.
Copy that new jar to the folder

JDK_HOME\jre\lib\endorsed

.
If the

endorsed

folder
does not exist, create it.

Debug your program in Eclipse. Note how the variables are named normally (no more arg0, arg1 etc). Happy debugging :)