Very simple demo of using CLHSDB from HotSpot Serviceability Agent to inspect Java objects and class metadata

command_prompt1

D:\temp>notepad MysteryBox.java

D:\temp>javac MysteryBox.java

D:\temp>groovysh
Groovy Shell (1.8.4, JVM: 1.7.0_09)
Type 'help' or '\h' for help.
------------------------------------------------------------------------
groovy:000> new MysteryBox()
===> MysteryBox@7a2145e6
groovy:000> quit

D:\temp>java -version
java version "1.7.0_09"
Java(TM) SE Runtime Environment (build 1.7.0_09-b05)
Java HotSpot(TM) 64-Bit Server VM (build 23.5-b02, mixed mode)

D:\temp>

command_prompt2

D:\temp>jps
500 Jps
9016 GroovyStarter

D:\temp>java -cp .;%JAVA_HOME%\lib\sa-jdi.jar sun.jvm.hotspot.CLHSDB
hsdb> attach 9016
Attaching to process 9016, please wait...
hsdb> universe
Heap Parameters:
ParallelScavengeHeap [ PSYoungGen [ eden =  [0x00000000fd560000,0x00000000fd68e780,0x00000000ff4c0000] , from =  [0x00000000ff4c0000,0x00000000ff74e030,0x00000000ff750000] , to =  [0x00000000ffd70000,0x00000000ffd70000,0x0000000100000000]  ] PSOldGen [  [0x00000000f8000000,0x00000000f8b1bac0,0x00000000fa9b0000]  ] PSPermGen [ [0x00000000f2e00000,0x00000000f3bb4c98,0x00000000f42c0000]  ]  ] hsdb>
hsdb> scanoops 0x00000000fd560000 0x00000000fd68e780 MysteryBox
0x00000000fd5bbd68 MysteryBox
hsdb> inspect 0x00000000fd5bbd68
instance of Oop for MysteryBox @ 0x00000000fd5bbd68 @ 0x00000000fd5bbd68 (size = 40)
_mark: 524544239105
x0: 0
x1: 0
y0: false
y1: false
y2: false
y3: false
z0: 0
a: [D @ 0x00000000fd5bbd90 Oop for [D @ 0x00000000fd5bbd90
hsdb> inspect 0x00000000fd5bbd90
instance of [D @ 0x00000000fd5bbd90 @ 0x00000000fd5bbd90 (size = 80)
_mark: 1
0: 0.0
1: 0.0
2: 0.0
3: 0.0
4: 0.0
5: 0.0
6: 0.0
7: 0.0
hsdb> class MysteryBox
MysteryBox @0x00000000f3b14610
hsdb> print 0x00000000f3b14610

public class MysteryBox @0x00000000f3b14610



Super Class
public class java.lang.Object @0x00000000f2e02db0
Fields

private  long x0; (offset = 16)
private  long x1; (offset = 24)
private  boolean y0; (offset = 32)
private  boolean y1; (offset = 33)
private  boolean y2; (offset = 34)
private  boolean y3; (offset = 35)
private  int z0; (offset = 12)
private  double[] a; (offset = 36)


Methods
public void <init>() @0x00000000f3b14588;

Constant Pool
Constant Pool of [public class MysteryBox @0x00000000f3b14610] @0x00000000f3b14350

hsdb> quit

D:\temp>

MysteryBox.java

public class MysteryBox {
  private long x0, x1;
  private boolean y0, y1, y2, y3;
  private int z0;
  private double[] a = new double[8];
}