ThreadReference.frames()
StackFrames provide access to a method's local variables and their current values.
The lifetime of a StackFrame is very limited. It is available only for suspended threads and becomes invalid once its thread is resumed.
Any method on StackFrame
which
takes StackFrame
as an parameter may throw
VMDisconnectedException
if the target VM is
disconnected and the VMDisconnectEvent
has been or is
available to be read from the EventQueue
.
Any method on StackFrame
which
takes StackFrame
as an parameter may throw
VMOutOfMemoryException
if the target VM has run out of memory.
- Since:
- 1.3
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Method Summary
Modifier and TypeMethodDescriptionReturns the values of all arguments in this frame.getValue
(LocalVariable variable) Gets theValue
of aLocalVariable
in this frame.getValues
(List<? extends LocalVariable> variables) Returns the values of multiple local variables in this frame.location()
Returns theLocation
of the current instruction in the frame.void
setValue
(LocalVariable variable, Value value) Sets theValue
of aLocalVariable
in this frame.Returns the value of 'this' for the current frame.thread()
Returns the thread under which this frame's method is running.visibleVariableByName
(String name) Finds aLocalVariable
that matches the given name and is visible at the current frame location.Returns a list containing eachLocalVariable
that can be accessed from this frame's location.Methods declared in interface com.sun.jdi.Mirror
toString, virtualMachine
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Method Details
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location
Location location()Returns theLocation
of the current instruction in the frame. The method for which this frame was created can also be accessed through the returned location. For the top frame in the stack, this location identifies the next instruction to be executed. For all other frames, this location identifies the instruction that caused the next frame's method to be invoked. If the frame represents a native method invocation, the returned location indicates the class and method, but the code index will not be valid (-1).- Specified by:
location
in interfaceLocatable
- Returns:
- the
Location
of the current instruction. - Throws:
InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.
-
thread
ThreadReference thread()Returns the thread under which this frame's method is running.- Returns:
- a
ThreadReference
which mirrors the frame's thread. - Throws:
InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.
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thisObject
ObjectReference thisObject()Returns the value of 'this' for the current frame. TheObjectReference
for 'this' is only available for non-native instance methods.- Returns:
- an
ObjectReference
, or null if the frame represents a native or static method. - Throws:
InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.
-
visibleVariables
Returns a list containing eachLocalVariable
that can be accessed from this frame's location.Visibility is based on the code index of the current instruction of this StackFrame. Each variable has a range of byte code indices in which it is accessible. If this stack frame's method matches this variable's method and if the code index of this StackFrame is within the variable's byte code range, the variable is visible.
A variable's byte code range is at least as large as the scope of that variable, but can continue beyond the end of the scope under certain circumstances:
- the compiler/VM does not immediately reuse the variable's slot.
- the compiler/VM is implemented to report the extended range that would result from the item above.
- Returns:
- the list of
LocalVariable
objects currently visible; the list will be empty if there are no visible variables; specifically, frames in native methods will always return a zero-length list. - Throws:
AbsentInformationException
- if there is no local variable information for this method.InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.NativeMethodException
- if the current method is native.
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visibleVariableByName
Finds aLocalVariable
that matches the given name and is visible at the current frame location. SeevisibleVariables()
for more information on visibility.- Parameters:
name
- the variable name to find- Returns:
- the matching
LocalVariable
, or null if there is no visible variable with the given name; frames in native methods will always return null. - Throws:
AbsentInformationException
- if there is no local variable information for this method.InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.NativeMethodException
- if the current method is native.
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getValue
Gets theValue
of aLocalVariable
in this frame. The variable must be valid for this frame's method and visible according to the rules described invisibleVariables()
.- Parameters:
variable
- theLocalVariable
to be accessed- Returns:
- the
Value
of the instance field. - Throws:
IllegalArgumentException
- if the variable is either invalid for this frame's method or not visible.InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.
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getValues
Returns the values of multiple local variables in this frame. Each variable must be valid for this frame's method and visible according to the rules described invisibleVariables()
.- Parameters:
variables
- a list ofLocalVariable
objects to be accessed- Returns:
- a map associating each
LocalVariable
with itsValue
- Throws:
IllegalArgumentException
- if any variable is either invalid for this frame's method or not visible.InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.
-
setValue
void setValue(LocalVariable variable, Value value) throws InvalidTypeException, ClassNotLoadedException Sets theValue
of aLocalVariable
in this frame. The variable must be valid for this frame's method and visible according to the rules described invisibleVariables()
.In the case of virtual threads, the target VM supports setting values of local variables when this frame is the topmost frame and the thread is suspended at an event. The target VM may support setting local variables in other cases.
Object values must be assignment compatible with the variable type (This implies that the variable type must be loaded through the enclosing class's class loader). Primitive values must be either assignment compatible with the variable type or must be convertible to the variable type without loss of information. See JLS section 5.2 for more information on assignment compatibility.
- Parameters:
variable
- the field containing the requested valuevalue
- the new value to assign- Throws:
IllegalArgumentException
- if the field is not valid for this object's class.InvalidTypeException
- if the value's type does not match the variable's type.ClassNotLoadedException
- if the variable type has not yet been loaded through the appropriate class loader.InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.OpaqueFrameException
- if this frame is on the call stack of a suspended virtual thread, and the target VM does not support setting the value of local variables in this frame.VMCannotBeModifiedException
- if the VirtualMachine is read-only.- See Also:
-
getArgumentValues
Returns the values of all arguments in this frame. Values are returned even if no local variable information is present.- Returns:
- a list containing a
Value
object for each argument to this frame, in the order in which the arguments were declared. If the method corresponding to this frame has no arguments, an empty list is returned. - Throws:
InvalidStackFrameException
- if this stack frame has become invalid. Once the frame's thread is resumed, the stack frame is no longer valid.- Since:
- 1.6
-