Accessing properties

Accessing fields of the heap object

[ <alias>. ] <field> . <field>. <field>

You can define an alias in the FROM clause, to identify the current object on which the OQL statement operates. Fields are attributes of the Java object in the heap dump. Without the alias, the field defaults to one of the fields of the current object. You can use the Inspector view to find out about the available fields of an object. Alternatively, in the standard edition of the product only, use the autocompletion function as described in Using the autocompletion function of the OQL view.

SELECT s.count, s.value FROM java.lang.String s

Accessing bean properties

[ <alias>. ] @<attribute> ...

SELECT s.@usedHeapSize, s.@retainedHeapSize FROM java.lang.String s

The following table lists some commonly used Java attributes. In the standard edition of the product, you can use the autocompletion function to show common bean names, as described in Using the autocompletion function of the OQL view.

Table 1. Common Java attributes

Any heap object	IObject	objectId	ID of the snapshot object
		objectAddress	address of the snapshot object
		class	Java class of this object
		clazz	IClass of this object. See also classof(object)
		usedHeapSize	shallow heap size
		retainedHeapSize	retained heap size
		displayName	display name
Class object	IClass	classLoaderId	ID of the class loader
Any array	IArray	length	length of the array
Primitive array	IPrimitiveArray	valueArray	the values in the array
Reference array	IObjectArray	referenceArray	the objects in the array (the addresses of the objects as long values). Access a particular element by using the get() method, then convert to an object by using the OBJECTS keyword.

Calling Java methods

[ <alias> . ] <method>( [ <expression>, <expression> ] ) ...

SELECT s.toString(s) FROM java.lang.String s

The following table lists some common Java methods that you can use on the underlying Java objects that are used by Memory Analyzer to represent objects in the heap dump. In the standard edition of the product, you can also use the autocompletion function to suggest some methods, as described in Using the autocompletion function of the OQL view.

Heap object	IObject	Method	Return object
${snapshot}	ISnapshot	getClasses()	A collection of all classes
		getClassesByName(String name, boolean includeSubClasses)	A collection of classes
Class object	IClass	hasSuperClass()	The result is true if the class has a super class
		isArrayType()	The result is true if the class is an array type
Any heap object	IObject	getObjectAddress()	The address of a snapshot object as a long integer
Primitive array	IPrimitiveArray	getValueAt(int index)	A value from the array
Java primitive array, Java object array, or Java list (returned from reflection)	[] or List	get(int index)	A value from the array or list

Array access

You can access primitive arrays and object arrays directly from the snapshot, and Java arrays and Java lists by using reflective method calls. You access arrays in this way by using the [index] notation. The index is an integer, which starts at 0 for the first element. If the array is null or the index is out of range, the access result is null.

You can also access a range of elements within an array, by using the [index_1:index_2] notation, where index_1 and index_2 indicate the start and end of the range, and are inclusive. Negative index values indicate that the range starts at the end of the array and moves backwards, so an index value of -1 specifies the last element in the array.

Reading values from primitive arrays

Index notation

For example:

SELECT s[2] FROM int[] s WHERE (s.@length > 2)

This example reads the value of the element at index 2 from all int[] arrays that have at least three elements.

Method call

For example:

SELECT s.getValueAt(2) FROM int[] s WHERE (s.@length > 2)

This example has the same result as the previous example.

Reading objects from object arrays

Index notation

For example:

SELECT s[2] FROM java.lang.Object[] s WHERE (s.@length > 2)

This example reads the element at index 2 from all Object arrays that have at least three elements. The element referenced by the s[2] code is an IObject object, so fields and Java bean properties can be accessed.

SELECT OBJECTS s[2] FROM java.lang.Object[] s

In this example, the OBJECTS keyword converts the object to show a tree view rather than a table result. The WHERE clause is not required because out-of-range accesses return null, and the OBJECTS keyword ignores null values.

Method call

For example:

SELECT OBJECTS s.@referenceArray.get(2) FROM java.lang.Object[] s WHERE (s.@length > 2)

This example reads, as an address of data type long, the element at index 2 from all Object arrays that have at least three elements, then converts the results into objects.

SELECT OBJECTS s.getReferenceArray(2,1) FROM java.lang.Object[] s WHERE (s.@length > 2)

This example reads, as an array of data type long, one element, starting at index 2, from all Object arrays that have at least three elements, then converts the contents of those arrays into objects.

Reading from Java arrays

Index notation

For example:

SELECT s.@GCRoots[2] FROM OBJECTS ${snapshot} s

Method call

For example:

SELECT s.@GCRoots.get(2) FROM OBJECTS ${snapshot} s  WHERE s.@GCRoots.@length > 2

Reading from Java lists

Index notation

For example:

SELECT s.@GCRoots.subList(1,3)[1] FROM OBJECTS ${snapshot} s

Method call

For example:

SELECT s.@GCRoots.subList(1,3).get(1) FROM OBJECTS ${snapshot} s

Built-in OQL functions

<function>( <parameter> )

Built-in functions:

toHex(number)

toString(object)

dominators(object)

outbounds(object)

inbounds(object)

classof(object)

dominatorof(object)

Using the autocompletion function of the OQL view