package com.vladium.utils;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Arrays;
import java.util.IdentityHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;
// ----------------------------------------------------------------------------
/**
* This non-instantiable class presents an API for object sizing and profiling
* as described in the article. See individual methods for details.<P>
*
* This implementation is J2SE 1.4+ only. You would need to code your own
* identity hashmap to port this to earlier Java versions.<P>
*
* Security: this implementation uses AccessController.doPrivileged() so it
* could be granted privileges to access non-public class fields separately
* from your main application code. The minimum set of persmissions necessary
* for this class to function correctly follows:
* <pre>
* permission java.lang.RuntimePermission "accessDeclaredMembers";
* permission java.lang.reflect.ReflectPermission "suppressAccessChecks";
* </pre>
*
* @see IObjectProfileNode
*
* @author (C) <a href="http://www.javaworld.com/columns/jw-qna-index.shtml">Vlad Roubtsov</a>, 2003
*/
public
abstract class ObjectProfiler
{
// public: ................................................................
// the following constants are physical sizes (in bytes) and are JVM-dependent:
// [the current values are Ok for most 32-bit JVMs]
public static final int OBJECT_SHELL_SIZE = 8; // java.lang.Object shell size in bytes
public static final int OBJREF_SIZE = 4;
public static final int LONG_FIELD_SIZE = 8;
public static final int INT_FIELD_SIZE = 4;
public static final int SHORT_FIELD_SIZE = 2;
public static final int CHAR_FIELD_SIZE = 2;
public static final int BYTE_FIELD_SIZE = 1;
public static final int BOOLEAN_FIELD_SIZE = 1;
public static final int DOUBLE_FIELD_SIZE = 8;
public static final int FLOAT_FIELD_SIZE = 4;
/** Set this to 'true' to make the node names default to using
* class names without package prefixing for more compact dumps */
public static final boolean SHORT_TYPE_NAMES = false;
/** If this is 'true', node names will use short class names
* for common classes in java.lang.* and java.util.*, regardless
* of {@link #SHORT_TYPE_NAMES} setting. */
public static final boolean SHORT_COMMON_TYPE_NAMES = true;
/**
* Estimates the full size of the object graph rooted at 'obj'.
* Duplicate data instances are correctly accounted for. The implementation
* is not recursive.<P>
*
* Invariant: sizeof(obj) == profile(obj).size() if 'obj' is not null
*
* @param obj input object instance to be measured
* @return 'obj' size [0 if 'obj' is null']
*/
public static int sizeof (final Object obj)
{
if (obj == null) return 0;
final IdentityHashMap visited = new IdentityHashMap ();
return computeSizeof (obj, visited, CLASS_METADATA_CACHE);
}
/**
* Estimates the full size of the object graph rooted at 'obj' by
* pre-populating the "visited" set with the object graph rooted
* at 'base'. The net effect is to compute the size of 'obj' by summing
* over all instance data contained in 'obj' but not in 'base'.
*
* @param base graph boundary [may not be null]
* @param obj input object instance to be measured
* @return 'obj' size [0 if 'obj' is null']
*/
public static int sizedelta (final Object base, final Object obj)
{
if (obj == null) return 0;
if (base == null) throw new IllegalArgumentException ("null input: base");
final IdentityHashMap visited = new IdentityHashMap ();
computeSizeof (base, visited, CLASS_METADATA_CACHE);
return visited.containsKey (obj) ? 0 : computeSizeof (obj, visited, CLASS_METADATA_CACHE);
}
/**
* Creates a spanning tree representation for instance data contained in
* 'obj'. The tree is produced using bread-first traversal over the full
* object graph implied by non-null instance and array references originating
* in 'obj'.
*
* @see IObjectProfileNode
*
* @param obj input object instance to be profiled [may not be null]
* @return the profile tree root node [never null]
*/
public static IObjectProfileNode profile (final Object obj)
{
if (obj == null) throw new IllegalArgumentException ("null input: obj");
final IdentityHashMap visited = new IdentityHashMap ();
final ObjectProfileNode root = createProfileTree (obj, visited, CLASS_METADATA_CACHE);
finishProfileTree (root);
return root;
}
// convenience methods:
public static String pathName (final IObjectProfileNode [] path)
{
final StringBuffer s = new StringBuffer ();
for (int i = 0; i < path.length; ++ i)
{
if (i != 0) s.append ('/');
s.append (path [i].name ());
}
return s.toString ();
}
public static String fieldName (final Field field, final boolean shortClassNames)
{
return typeName (field.getDeclaringClass (), shortClassNames).concat ("#").concat (field.getName ());
}
public static String typeName (Class cls, final boolean shortClassNames)
{
int dims = 0;
for ( ; cls.isArray (); ++ dims) cls = cls.getComponentType ();
String clsName = cls.getName ();
if (shortClassNames)
{
final int lastDot = clsName.lastIndexOf ('.');
if (lastDot >= 0) clsName = clsName.substring (lastDot + 1);
}
else if (SHORT_COMMON_TYPE_NAMES)
{
if (clsName.startsWith ("java.lang.")) clsName = clsName.substring (10);
else if (clsName.startsWith ("java.util.")) clsName = clsName.substring (10);
}
for (int i = 0; i < dims; ++ i) clsName = clsName.concat ("[]");
return clsName;
}
// protected: .............................................................
// package: ...............................................................
static final String INPUT_OBJECT_NAME = "<INPUT>"; // root node name
// private: ...............................................................
/*
* Internal class used to cache class metadata information.
*/
private static final class ClassMetadata
{
ClassMetadata (final int primitiveFieldCount,
final int shellSize,
final Field [] refFields)
{
m_primitiveFieldCount = primitiveFieldCount;
m_shellSize = shellSize;
m_refFields = refFields;
}
// all fields are inclusive of superclasses:
final int m_primitiveFieldCount;
final int m_shellSize; // class shell size
final Field [] m_refFields; // cached non-static fields (made accessible)
} // end of nested class
private static final class ClassAccessPrivilegedAction
implements PrivilegedExceptionAction
{
public Object run () throws Exception
{
return m_cls.getDeclaredFields ();
}
void setContext (final Class cls)
{
m_cls = cls;
}
private Class m_cls;
} // end of nested class
private static final class FieldAccessPrivilegedAction
implements PrivilegedExceptionAction
{
public Object run () throws Exception
{
m_field.setAccessible (true);
return null;
}
void setContext (final Field field)
{
m_field = field;
}
private Field m_field;
} // end of nested class
private ObjectProfiler () {} // this class is not extendible
/*
* The main worker method for sizeof() and sizedelta().
*/
private static int computeSizeof (Object obj,
final IdentityHashMap visited,
final Map /* Class->ClassMetadata */ metadataMap)
{
// this uses depth-first traversal; the exact graph traversal algorithm
// does not matter for computing the total size and this method could be
// easily adjusted to do breadth-first instead (addLast() instead of addFirst()),
// however, dfs/bfs require max queue length to be the length of the longest
// graph path/width of traversal front correspondingly, so I expect
// dfs to use fewer resources than bfs for most Java objects;
if (obj == null) return 0;
final LinkedList queue = new LinkedList ();
visited.put (obj, obj);
queue.add (obj);
int result = 0;
final ClassAccessPrivilegedAction caAction = new ClassAccessPrivilegedAction ();
final FieldAccessPrivilegedAction faAction = new FieldAccessPrivilegedAction ();
while (! queue.isEmpty ())
{
obj = queue.removeFirst ();
final Class objClass = obj.getClass ();
if (objClass.isArray ())
{
final int arrayLength = Array.getLength (obj);
final Class componentType = objClass.getComponentType ();
result += sizeofArrayShell (arrayLength, componentType);
if (! componentType.isPrimitive ())
{
// traverse each array slot:
for (int i = 0; i < arrayLength; ++ i)
{
final Object ref = Array.get (obj, i);
if ((ref != null) && ! visited.containsKey (ref))
{
visited.put (ref, ref);
queue.addFirst (ref);
}
}
}
}
else // the object is of a non-array type
{
final ClassMetadata metadata = getClassMetadata (objClass, metadataMap, caAction, faAction);
final Field [] fields = metadata.m_refFields;
result += metadata.m_shellSize;
// traverse all non-null ref fields:
for (int f = 0, fLimit = fields.length; f < fLimit; ++ f)
{
final Field field = fields [f];
final Object ref;
try // to get the field value:
{
ref = field.get (obj);
}
catch (Exception e)
{
throw new RuntimeException ("cannot get field [" + field.getName () + "] of class [" + field.getDeclaringClass ().getName () + "]: " + e.toString ());
}
if ((ref != null) && ! visited.containsKey (ref))
{
visited.put (ref, ref);
queue.addFirst (ref);
}
}
}
}
return result;
}
/*
* Performs phase 1 of profile creation: bread-first traversal and node
* creation.
*/
private static ObjectProfileNode createProfileTree (Object obj,
final IdentityHashMap visited,
final Map /* Class->ClassMetadata */ metadataMap)
{
final ObjectProfileNode root = new ObjectProfileNode (null, obj, null);
final LinkedList queue = new LinkedList ();
queue.addFirst (root);
visited.put (obj, root);
final ClassAccessPrivilegedAction caAction = new ClassAccessPrivilegedAction ();
final FieldAccessPrivilegedAction faAction = new FieldAccessPrivilegedAction ();
while (! queue.isEmpty ())
{
final ObjectProfileNode node = (ObjectProfileNode) queue.removeFirst ();
obj = node.m_obj;
final Class objClass = obj.getClass ();
if (objClass.isArray ())
{
final int arrayLength = Array.getLength (obj);
final Class componentType = objClass.getComponentType ();
// add shell pseudo-node:
final AbstractShellProfileNode shell = new ArrayShellProfileNode (node, objClass, arrayLength);
shell.m_size = sizeofArrayShell (arrayLength, componentType);
node.m_shell = shell;
node.addFieldRef (shell);
if (! componentType.isPrimitive ())
{
// traverse each array slot:
for (int i = 0; i < arrayLength; ++ i)
{
final Object ref = Array.get (obj, i);
if (ref != null)
{
ObjectProfileNode child = (ObjectProfileNode) visited.get (ref);
if (child != null)
++ child.m_refcount;
else
{
child = new ObjectProfileNode (node, ref, new ArrayIndexLink (node.m_link, i));
node.addFieldRef (child);
queue.addLast (child);
visited.put (ref, child);
}
}
}
}
}
else // the object is of a non-array type
{
final ClassMetadata metadata = getClassMetadata (objClass, metadataMap, caAction, faAction);
final Field [] fields = metadata.m_refFields;
// add shell pseudo-node:
final AbstractShellProfileNode shell = new ObjectShellProfileNode (node, metadata.m_primitiveFieldCount, metadata.m_refFields.length);
shell.m_size = metadata.m_shellSize;
node.m_shell = shell;
node.addFieldRef (shell);
// traverse all non-null ref fields:
for (int f = 0, fLimit = fields.length; f < fLimit; ++ f)
{
final Field field = fields [f];
final Object ref;
try // to get the field value:
{
ref = field.get (obj);
}
catch (Exception e)
{
throw new RuntimeException ("cannot get field [" + field.getName () + "] of class [" + field.getDeclaringClass ().getName () + "]: " + e.toString ());
}
if (ref != null)
{
ObjectProfileNode child = (ObjectProfileNode) visited.get (ref);
if (child != null)
++ child.m_refcount;
else
{
child = new ObjectProfileNode (node, ref, new ClassFieldLink (field));
node.addFieldRef (child);
queue.addLast (child);
visited.put (ref, child);
}
}
}
}
}
return root;
}
/*
* Performs phase 2 of profile creation: totalling of node sizes (via
* non-recursive post-order traversal of the tree created in phase 1)
* and 'locking down' of profile nodes into their most compact form.
*/
private static void finishProfileTree (ObjectProfileNode node)
{
final LinkedList queue = new LinkedList ();
IObjectProfileNode lastFinished = null;
while (node != null)
{
// note that an unfinished non-shell node has its child count
// in m_size and m_children[0] is its shell node:
if ((node.m_size == 1) || (lastFinished == node.m_children [1]))
{
node.finish ();
lastFinished = node;
}
else
{
queue.addFirst (node);
for (int i = 1; i < node.m_size; ++ i)
{
final IObjectProfileNode child = node.m_children [i];
queue.addFirst (child);
}
}
if (queue.isEmpty ())
return;
else
node = (ObjectProfileNode) queue.removeFirst ();
}
}
/*
* A helper method for manipulating a class metadata cache.
*/
private static ClassMetadata getClassMetadata (final Class cls,
final Map /* Class->ClassMetadata */ metadataMap,
final ClassAccessPrivilegedAction caAction,
final FieldAccessPrivilegedAction faAction)
{
if (cls == null) return null;
ClassMetadata result;
synchronized (metadataMap)
{
result = (ClassMetadata) metadataMap.get (cls);
}
if (result != null) return result;
int primitiveFieldCount = 0;
int shellSize = OBJECT_SHELL_SIZE; // java.lang.Object shell
final List /* Field */ refFields = new LinkedList ();
final Field [] declaredFields;
try
{
caAction.setContext (cls);
declaredFields = (Field []) AccessController.doPrivileged (caAction);
}
catch (PrivilegedActionException pae)
{
throw new RuntimeException ("could not access declared fields of class " + cls.getName () + ": " + pae.getException ());
}
for (int f = 0; f < declaredFields.length; ++ f)
{
final Field field = declaredFields [f];
if ((Modifier.STATIC & field.getModifiers ()) != 0) continue;
final Class fieldType = field.getType ();
if (fieldType.isPrimitive ())
{
// memory alignment ignored:
shellSize += sizeofPrimitiveType (fieldType);
++ primitiveFieldCount;
}
else
{
// prepare for graph traversal later:
if (! field.isAccessible ())
{
try
{
faAction.setContext (field);
AccessController.doPrivileged (faAction);
}
catch (PrivilegedActionException pae)
{
throw new RuntimeException ("could not make field " + field + " accessible: " + pae.getException ());
}
}
// memory alignment ignored:
shellSize += OBJREF_SIZE;
refFields.add (field);
}
}
// recurse into superclass:
final ClassMetadata superMetadata = getClassMetadata (cls.getSuperclass (), metadataMap, caAction, faAction);
if (superMetadata != null)
{
primitiveFieldCount += superMetadata.m_primitiveFieldCount;
shellSize += superMetadata.m_shellSize - OBJECT_SHELL_SIZE;
refFields.addAll (Arrays.asList (superMetadata.m_refFields));
}
final Field [] _refFields = new Field [refFields.size ()];
refFields.toArray (_refFields);
result = new ClassMetadata (primitiveFieldCount, shellSize, _refFields);
synchronized (metadataMap)
{
metadataMap.put (cls, result);
}
return result;
}
/*
* Computes the "shallow" size of an array instance.
*/
private static int sizeofArrayShell (final int length, final Class componentType)
{
// this ignores memory alignment issues by design:
final int slotSize = componentType.isPrimitive ()
? sizeofPrimitiveType (componentType)
: OBJREF_SIZE;
return OBJECT_SHELL_SIZE + INT_FIELD_SIZE + OBJREF_SIZE + length * slotSize;
}
/*
* Returns the JVM-specific size of a primitive type.
*/
private static int sizeofPrimitiveType (final Class type)
{
if (type == int.class)
return INT_FIELD_SIZE;
else if (type == long.class)
return LONG_FIELD_SIZE;
else if (type == short.class)
return SHORT_FIELD_SIZE;
else if (type == byte.class)
return BYTE_FIELD_SIZE;
else if (type == boolean.class)
return BOOLEAN_FIELD_SIZE;
else if (type == char.class)
return CHAR_FIELD_SIZE;
else if (type == double.class)
return DOUBLE_FIELD_SIZE;
else if (type == float.class)
return FLOAT_FIELD_SIZE;
else
throw new IllegalArgumentException ("not primitive: " + type);
}
// class metadata cache:
private static final Map CLASS_METADATA_CACHE = new WeakHashMap (101);
} // end of class
// ----------------------------------------------------------------------------