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- All Superinterfaces:
Mirror
,ObjectReference
,Value
public interface ThreadReference extends ObjectReference
A thread object from the target VM. A ThreadReference is anObjectReference
with additional access to thread-specific information from the target VM.- Since:
- 1.3
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Field Summary
Fields Modifier and Type Field Description static int
THREAD_STATUS_MONITOR
Thread is waiting on a java monitorstatic int
THREAD_STATUS_NOT_STARTED
Thread has not yet been startedstatic int
THREAD_STATUS_RUNNING
Thread is runnablestatic int
THREAD_STATUS_SLEEPING
Thread is sleeping - Thread.sleep() or JVM_Sleep() was calledstatic int
THREAD_STATUS_UNKNOWN
Thread status is unknownstatic int
THREAD_STATUS_WAIT
Thread is waiting - Object.wait() or JVM_MonitorWait() was calledstatic int
THREAD_STATUS_ZOMBIE
Thread has completed execution-
Fields declared in interface com.sun.jdi.ObjectReference
INVOKE_NONVIRTUAL, INVOKE_SINGLE_THREADED
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description ObjectReference
currentContendedMonitor()
Returns anObjectReference
for the monitor, if any, for which this thread is currently waiting.void
forceEarlyReturn(Value value)
Force a method to return before it reaches a return statement.StackFrame
frame(int index)
Returns theStackFrame
at the given index in the thread's current call stack.int
frameCount()
Returns the number of stack frames in the thread's current call stack.List<StackFrame>
frames()
Returns a List containing eachStackFrame
in the thread's current call stack.List<StackFrame>
frames(int start, int length)
Returns a List containing a range ofStackFrame
mirrors from the thread's current call stack.void
interrupt()
Interrupts this thread unless the thread has been suspended by the debugger.boolean
isAtBreakpoint()
Determines whether the thread is suspended at a breakpoint.boolean
isSuspended()
Determines whether the thread has been suspended by the the debugger.String
name()
Returns the name of this thread.List<ObjectReference>
ownedMonitors()
Returns a List containing anObjectReference
for each monitor owned by the thread.List<MonitorInfo>
ownedMonitorsAndFrames()
Returns a List containing aMonitorInfo
object for each monitor owned by the thread.void
popFrames(StackFrame frame)
Pop stack frames.void
resume()
Resumes this thread.int
status()
Returns the thread's status.void
stop(ObjectReference throwable)
Stops this thread with an asynchronous exception.void
suspend()
Suspends this thread.int
suspendCount()
Returns the number of pending suspends for this thread.ThreadGroupReference
threadGroup()
Returns this thread's thread group.-
Methods declared in interface com.sun.jdi.Mirror
toString, virtualMachine
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Methods declared in interface com.sun.jdi.ObjectReference
disableCollection, enableCollection, entryCount, equals, getValue, getValues, hashCode, invokeMethod, isCollected, owningThread, referenceType, referringObjects, setValue, uniqueID, waitingThreads
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Field Detail
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THREAD_STATUS_UNKNOWN
static final int THREAD_STATUS_UNKNOWN
Thread status is unknown- See Also:
- Constant Field Values
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THREAD_STATUS_ZOMBIE
static final int THREAD_STATUS_ZOMBIE
Thread has completed execution- See Also:
- Constant Field Values
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THREAD_STATUS_RUNNING
static final int THREAD_STATUS_RUNNING
Thread is runnable- See Also:
- Constant Field Values
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THREAD_STATUS_SLEEPING
static final int THREAD_STATUS_SLEEPING
Thread is sleeping - Thread.sleep() or JVM_Sleep() was called- See Also:
- Constant Field Values
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THREAD_STATUS_MONITOR
static final int THREAD_STATUS_MONITOR
Thread is waiting on a java monitor- See Also:
- Constant Field Values
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THREAD_STATUS_WAIT
static final int THREAD_STATUS_WAIT
Thread is waiting - Object.wait() or JVM_MonitorWait() was called- See Also:
- Constant Field Values
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THREAD_STATUS_NOT_STARTED
static final int THREAD_STATUS_NOT_STARTED
Thread has not yet been started- See Also:
- Constant Field Values
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Method Detail
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name
String name()
Returns the name of this thread.- Returns:
- the string containing the thread name.
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suspend
void suspend()
Suspends this thread. The thread can be resumed throughresume()
or resumed with other threads throughVirtualMachine.resume()
.Unlike
Thread.suspend()
, suspends of both the virtual machine and individual threads are counted. Before a thread will run again, it must be resumed (throughresume()
orresume()
) the same number of times it has been suspended.Suspending single threads with this method has the same dangers as
Thread.suspend()
. If the suspended thread holds a monitor needed by another running thread, deadlock is possible in the target VM (at least until the suspended thread is resumed again).The suspended thread is guaranteed to remain suspended until resumed through one of the JDI resume methods mentioned above; the application in the target VM cannot resume the suspended thread through
Thread.resume()
.- Throws:
VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
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resume
void resume()
Resumes this thread. If this thread was not previously suspended throughsuspend()
or throughVirtualMachine.suspend()
, or because of a SUSPEND_ALL or SUSPEND_EVENT_THREAD event, then invoking this method has no effect. Otherwise, the count of pending suspends on this thread is decremented. If it is decremented to 0, the thread will continue to execute. Note: the normal way to resume from an event related suspension is viaEventSet.resume()
.- Throws:
VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
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suspendCount
int suspendCount()
Returns the number of pending suspends for this thread. Seesuspend()
for an explanation of counted suspends.- Returns:
- pending suspend count as an integer
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stop
void stop(ObjectReference throwable) throws InvalidTypeException
Stops this thread with an asynchronous exception. A debugger thread in the target VM will stop this thread with the givenThrowable
object.- Parameters:
throwable
- the asynchronous exception to throw.- Throws:
InvalidTypeException
- ifthrowable
is not an instance of java.lang.Throwable in the target VM.VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
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interrupt
void interrupt()
Interrupts this thread unless the thread has been suspended by the debugger.- Throws:
VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
.- See Also:
Thread.interrupt()
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status
int status()
Returns the thread's status. If the thread is not suspended the thread's current status is returned. If the thread is suspended, the thread's status before the suspension is returned (orTHREAD_STATUS_UNKNOWN
if this information is not available.isSuspended()
can be used to determine if the thread has been suspended.
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isSuspended
boolean isSuspended()
Determines whether the thread has been suspended by the the debugger.- Returns:
true
if the thread is currently suspended;false
otherwise.
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isAtBreakpoint
boolean isAtBreakpoint()
Determines whether the thread is suspended at a breakpoint.- Returns:
true
if the thread is currently stopped at a breakpoint;false
otherwise.
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threadGroup
ThreadGroupReference threadGroup()
Returns this thread's thread group.- Returns:
- a
ThreadGroupReference
that mirrors this thread's thread group in the target VM.
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frameCount
int frameCount() throws IncompatibleThreadStateException
Returns the number of stack frames in the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.- Returns:
- an integer frame count
- Throws:
IncompatibleThreadStateException
- if the thread is not suspended in the target VM
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frames
List<StackFrame> frames() throws IncompatibleThreadStateException
Returns a List containing eachStackFrame
in the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.- Returns:
- a List of
StackFrame
with the current frame first followed by each caller's frame. - Throws:
IncompatibleThreadStateException
- if the thread is not suspended in the target VM
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frame
StackFrame frame(int index) throws IncompatibleThreadStateException
Returns theStackFrame
at the given index in the thread's current call stack. Index 0 retrieves the current frame; higher indices retrieve caller frames. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.- Parameters:
index
- the desired frame- Returns:
- the requested
StackFrame
- Throws:
IncompatibleThreadStateException
- if the thread is not suspended in the target VMIndexOutOfBoundsException
- if the index is greater than or equal toframeCount()
or is negative.
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frames
List<StackFrame> frames(int start, int length) throws IncompatibleThreadStateException
Returns a List containing a range ofStackFrame
mirrors from the thread's current call stack. The thread must be suspended (normally through an interruption to the VM) to get this information, and it is only valid until the thread is resumed again.- Parameters:
start
- the index of the first frame to retrieve. Index 0 represents the current frame.length
- the number of frames to retrieve- Returns:
- a List of
StackFrame
with the current frame first followed by each caller's frame. - Throws:
IncompatibleThreadStateException
- if the thread is not suspended in the target VMIndexOutOfBoundsException
- if the specified range is not within the range of stack frame indicies. That is, the exception is thrown if any of the following are true:start < 0 start >=
frameCount()
length < 0 (start+length) >frameCount()
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ownedMonitors
List<ObjectReference> ownedMonitors() throws IncompatibleThreadStateException
Returns a List containing anObjectReference
for each monitor owned by the thread. A monitor is owned by a thread if it has been entered (via the synchronized statement or entry into a synchronized method) and has not been relinquished throughObject.wait()
.Not all target virtual machines support this operation. Use
VirtualMachine.canGetOwnedMonitorInfo()
to determine if the operation is supported.- Returns:
- a List of
ObjectReference
objects. The list has zero length if no monitors are owned by this thread. - Throws:
UnsupportedOperationException
- if the target virtual machine does not support this operation.IncompatibleThreadStateException
- if the thread is not suspended in the target VM
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ownedMonitorsAndFrames
List<MonitorInfo> ownedMonitorsAndFrames() throws IncompatibleThreadStateException
Returns a List containing aMonitorInfo
object for each monitor owned by the thread. A monitor is owned by a thread if it has been entered (via the synchronized statement or entry into a synchronized method) and has not been relinquished throughObject.wait()
.Not all target virtual machines support this operation. Use
VirtualMachine.canGetMonitorFrameInfo()
to determine if the operation is supported.- Returns:
- a List of
MonitorInfo
objects. The list has zero length if no monitors are owned by this thread. - Throws:
UnsupportedOperationException
- if the target virtual machine does not support this operation.IncompatibleThreadStateException
- if the thread is not suspended in the target VM- Since:
- 1.6
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currentContendedMonitor
ObjectReference currentContendedMonitor() throws IncompatibleThreadStateException
Returns anObjectReference
for the monitor, if any, for which this thread is currently waiting. The thread can be waiting for a monitor through entry into a synchronized method, the synchronized statement, orObject.wait()
. Thestatus()
method can be used to differentiate between the first two cases and the third.Not all target virtual machines support this operation. Use
VirtualMachine.canGetCurrentContendedMonitor()
to determine if the operation is supported.- Returns:
- the
ObjectReference
corresponding to the contended monitor, or null if it is not waiting for a monitor. - Throws:
UnsupportedOperationException
- if the target virtual machine does not support this operation.IncompatibleThreadStateException
- if the thread is not suspended in the target VM
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popFrames
void popFrames(StackFrame frame) throws IncompatibleThreadStateException
Pop stack frames.All frames up to and including the
frame
are popped off the stack. The frame previous to the parameterframe
will become the current frame.After this operation, this thread will be suspended at the invoke instruction of the target method that created
frame
. Theframe
's method can be reentered with a step into the instruction.The operand stack is restored, however, any changes to the arguments that occurred in the called method, remain. For example, if the method
foo
:void foo(int x) { System.out.println("Foo: " + x); x = 4; System.out.println("pop here"); }
was called withfoo(7)
andfoo
is popped at the secondprintln
and resumed, it will print:Foo: 4
.Locks acquired by a popped frame are released when it is popped. This applies to synchronized methods that are popped, and to any synchronized blocks within them.
Finally blocks are not executed.
No aspect of state, other than this thread's execution point and locks, is affected by this call. Specifically, the values of fields are unchanged, as are external resources such as I/O streams. Additionally, the target program might be placed in a state that is impossible with normal program flow; for example, order of lock acquisition might be perturbed. Thus the target program may proceed differently than the user would expect.
The specified thread must be suspended.
All
StackFrame
objects for this thread are invalidated.No events are generated by this method.
None of the frames through and including the frame for the caller of frame may be native.
Not all target virtual machines support this operation. Use
VirtualMachine.canPopFrames()
to determine if the operation is supported.- Parameters:
frame
- Stack frame to pop.frame
is on this thread's call stack.- Throws:
UnsupportedOperationException
- if the target virtual machine does not support this operation - seeVirtualMachine.canPopFrames()
.IncompatibleThreadStateException
- if this thread is not suspended.IllegalArgumentException
- ifframe
is not on this thread's call stack.NativeMethodException
- if one of the frames that would be popped is that of a native method or if the frame previous to frame is native.InvalidStackFrameException
- ifframe
has become invalid. Once this thread is resumed, the stack frame is no longer valid. This exception is also thrown if there are no more frames.VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
.- Since:
- 1.4
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forceEarlyReturn
void forceEarlyReturn(Value value) throws InvalidTypeException, ClassNotLoadedException, IncompatibleThreadStateException
Force a method to return before it reaches a return statement.The method which will return early is referred to as the called method. The called method is the current method (as defined by the Frames section in the Java Virtual Machine Specification) for the specified thread at the time this method is called.
The thread must be suspended. The return occurs when execution of Java programming language code is resumed on this thread. Between the call to this method and resumption of thread execution, the state of the stack is undefined.
No further instructions are executed in the called method. Specifically, finally blocks are not executed. Note: this can cause inconsistent states in the application.
A lock acquired by calling the called method (if it is a synchronized method) and locks acquired by entering synchronized blocks within the called method are released. Note: this does not apply to native locks or java.util.concurrent.locks locks.
Events, such as MethodExit, are generated as they would be in a normal return.
The called method must be a non-native Java programming language method. Forcing return on a thread with only one frame on the stack causes the thread to exit when resumed.
The
value
argument is the value that the method is to return. If the return type of the method is void, then value must be aVoidValue
. Object values must be assignment compatible with the method return type (This implies that the method return type must be loaded through the enclosing class's class loader). Primitive values must be either assignment compatible with the method return type or must be convertible to the variable type without loss of information. See JLS section 5.2 for more information on assignment compatibility.Not all target virtual machines support this operation. Use
VirtualMachine.canForceEarlyReturn()
to determine if the operation is supported.- Parameters:
value
- the value the method is to return.- Throws:
UnsupportedOperationException
- if the target virtual machine does not support this operation - seecanForceEarlyReturn()
IncompatibleThreadStateException
- if this thread is not suspended.NativeMethodException
- if the frame to be returned from is that of a native method.InvalidStackFrameException
- if there are no frames.InvalidTypeException
- if the value's type does not match the method's return type.ClassNotLoadedException
- if the method's return type has not yet been loaded through the appropriate class loader.VMCannotBeModifiedException
- if the VirtualMachine is read-only - seeVirtualMachine.canBeModified()
.- Since:
- 1.6
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