Heap Dumping

XML Schema

Below is the XML schema for heap dumps.

XML Schema for Heap Dumps 
<?xml version='1.0' encoding='UTF-8'?>
<!--
    Schema

    Copyright 2012 IS2T. All rights reserved.

   IS2T PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
-->

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <!-- root element: heap -->
    <xs:element name="heap">
        <xs:complexType>
            <xs:choice minOccurs="0" maxOccurs="unbounded">
                <xs:element ref="class"/>
                <xs:element ref="object"/>
                <xs:element ref="array"/>
                <xs:element ref="stringLiteral"/>
            </xs:choice>
        </xs:complexType>
    </xs:element>

<!-- class element -->
<xs:element name="class">
    <xs:complexType>
        <xs:choice minOccurs="0" maxOccurs="unbounded">
            <xs:element ref="field"/>
        </xs:choice>
        <xs:attribute name="name" type="xs:string" use = "required"/>
        <xs:attribute name="id" type="xs:string" use = "required"/>
        <xs:attribute name="superclass" type="xs:string"/>
    </xs:complexType>
</xs:element>

<!-- object element-->
<xs:element name="object">
    <xs:complexType>
        <xs:choice minOccurs="0" maxOccurs="unbounded">
            <xs:element ref="field"/>
        </xs:choice>
        <xs:attribute name="id" type="xs:string" use = "required"/>
        <xs:attribute name="class" type="xs:string" use = "required"/>
        <xs:attribute name="createdAt" type="xs:string" use = "optional"/>
        <xs:attribute name="createdInThread" type="xs:string" use = "optional"/>
        <xs:attribute name="createdInMethod" type="xs:string"/>
        <xs:attribute name="tag" type="xs:string" use = "required"/>
    </xs:complexType>
</xs:element>

<!-- array element-->
<xs:element name="array" type = "arrayTypeWithAttribute"/>
<!-- stringLiteral element-->
<xs:element name="stringLiteral">
    <xs:complexType>
        <xs:sequence>
            <xs:element minOccurs ="4" maxOccurs="4" ref="field "/>
        </xs:sequence>
        <xs:attribute name="id" type="xs:string" use = "required"/>
        <xs:attribute name="class" type="xs:string" use = "required"/>
    </xs:complexType>
</xs:element>

   <!-- field element:  child of class, object and stringLiteral-->
      <xs:element name="field">
          <xs:complexType>
              <xs:attribute name="name" type="xs:string" use = "required"/>
              <xs:attribute name="id" type="xs:string" use = "optional"/>
              <xs:attribute name="value" type="xs:string" use = "optional"/>
              <xs:attribute name="type" type="xs:string" use = "optional"/>
          </xs:complexType>
      </xs:element>

      <xs:simpleType name = "arrayType">
          <xs:list itemType="xs:integer"/>
      </xs:simpleType>



<!-- complex type "arrayTypeWithAttribute". type of array element-->
      <xs:complexType name = "arrayTypeWithAttribute">
          <xs:simpleContent>
              <xs:extension base="arrayType">
                  <xs:attribute name="id" type="xs:string" use = "required"/>
                  <xs:attribute name="class" type="xs:string" use = "required"/>
                  <xs:attribute name="createdAt" type="xs:string" use = "optional"/>
                  <xs:attribute name="createdInThread" type="xs:string" use = "optional"/>
                  <xs:attribute name="createdInMethod" type="xs:string" use = "optional"/>
                  <xs:attribute name="length" type="xs:string" use = "required"/>
                  <xs:attribute name="elementsType" type="xs:string" use = "optional"/>
                  <xs:attribute name="type" type="xs:string" use = "optional"/>
              </xs:extension>
          </xs:simpleContent>
      </xs:complexType>

  </xs:schema>

File Specification

Types referenced in heap dumps are represented in the internal classfile format (Internal classfile Format for Types). Fully qualified names are names separated by the / separator (For example, a/b/C).

Internal classfile Format for Types
Type = <BaseType> | <ClassType> | <ArrayType>
BaseType: B(byte), C(char), D(double), F(float), I(int), J(long), S(short), Z(boolean),
ClassType: L<ClassName>;
ArrayType: [<Type>

Tags used in the heap dumps are described in the table below.

Tag Descriptions

Tags

Attributes

Description

heap

The root element.

class

Element that references a Java class.

name

Class type (<ClassType>)

id

Unique identifier of the class.

superclass

Identifier of the superclass of this class.

object

Element that references a Java object.

id

Unique identifier of this object.

class

Fully qualified name of the class of this object.

array

Element that references a Java array.

id

Unique identifier of this array.

class

Fully qualified name of the class of this array.

elementsType

Type of the elements of this array.

length

Array length.

stringLiteral

Element that references a java.lang.String literal.

id

Unique identifier of this object.

class

Id of java.lang.String class.

field

Element that references the field of an object or a class.

name

Name of this field.

id

Object or Array identifier, if it holds a reference.

type

Type of this field, if it holds a base type.

value

Value of this field, if it holds a base type.