T=88>

Java Debug Wire Protocol
Specification Details


  • VirtualMachine Command Set (1)

  • ReferenceType Command Set (2)

  • ClassType Command Set (3)

  • ArrayType Command Set (4)

  • InterfaceType Command Set (5)

  • Method Command Set (6)

  • Field Command Set (8)

  • ObjectReference Command Set (9)

  • StringReference Command Set (10)

  • ThreadReference Command Set (11)

  • ThreadGroupReference Command Set (12)

  • ArrayReference Command Set (13)

  • ClassLoaderReference Command Set (14)

  • EventRequest Command Set (15)

  • StackFrame Command Set (16)

  • ClassObjectReference Command Set (17)

  • Event Command Set (64)

  • Error Constants
  • EventKind Constants
  • ThreadStatus Constants
  • SuspendStatus Constants
  • ClassStatus Constants
  • TypeTag Constants
  • Tag Constants
  • StepDepth Constants
  • StepSize Constants
  • SuspendPolicy Constants
  • InvokeOptions Constants

    VirtualMachine Command Set (1)

    Version Command (1)
    Returns the JDWP version implemented by the target VM. The version string format is implementation dependent.

    Out Data

    (None)

    Reply Data

    string description Text information on the VM version 
    int jdwpMajor Major JDWP Version number 
    int jdwpMinor Minor JDWP Version number 
    string vmVersion Target VM JRE version, as in the java.version property 
    string vmName Target VM name, as in the java.vm.name property 

    Error Data

    VM_DEAD The virtual machine is not running.
    ClassesBySignature Command (2)
    Returns reference types for all the classes loaded by the target VM which match the given signature. Multple reference types will be returned if two or more class loaders have loaded a class of the same name. The search is confined to loaded classes only; no attempt is made to load a class of the given signature.

    Out Data

    string signature top>JNI signature of the class to find (for example, "Ljava/lang/String;").  

    Reply Data

    int classes Number of reference types that follow. 
    Repeated classes times:
    byte refTypeTag Kind of following reference type.  
    referenceTypeID typeID Matching loaded reference type 
    int status The current class status.  

    Error Data

    VM_DEAD The virtual machine is not running.
    AllClasses Command (3)
    Returns reference types for all classes currently loaded by the target VM.

    Out Data

    (None)

    Reply Data

    int classes Number of reference types that follow. 
    Repeated classes times:
    byte refTypeTag Kind of following reference type.  
    referenceTypeID typeID Loaded reference type 
    string signature The JNI signature of the loaded reference type 
    int status The current class status.  

    Error Data

    VM_DEAD The virtual machine is not running.
    AllThreads Command (4)
    Returns all threads currently running in the target VM . The returned list contains threads created through java.lang.Thread, all native threads attached to the target VM through JNI, and system threads created by the target VM. Threads that have not yet been started and threads that have completed their execution are not included in the returned list.

    Out Data

    (None)

    Reply Data

    int threads Number of threads that follow. 
    Repeated threads times:
    threadID thread A running thread 

    Error Data

    VM_DEAD The virtual machine is not running.
    TopLevelThreadGroups Command (5)
    Returns all thread groups that do not have a parent. This command may be used as the first step in building a tree (or trees) of the existing thread groups.

    Out Data

    (None)

    Reply Data

    int groups Number of thread groups that follow. 
    Repeated groups times:
    threadGroupID group A top level thread group 

    Error Data

    VM_DEAD The virtual machine is not running.
    Dispose Command (6)
    Invalidates this virtual machine mirror. The communication channel to the target VM is closed, and the target VM prepares to accept another subsequent connection from this debugger or another debugger, including the following tasks:

    • All event requests are cancelled.
    • All threads suspended by the thread-level resume command or the VM-level resume command are resumed as many times as necessary for them to run.
    • Garbage collection is re-enabled in all cases where it was disabled
    Any current method invocations executing in the target VM are continued after the disconnection. Upon completion of any such method invocation, the invoking thread continues from the location where it was originally stopped.

    Resources originating in this VirtualMachine (ObjectReferences, ReferenceTypes, etc.) will become invalid.

    Out Data

    (None)

    Reply Data

    (None)

    Error Data

    (None)
    IDSizes Command (7)
    Returns the sizes of variably-sized data types in the target VM.The returned values indicate the number of bytes used by the identifiers in command and reply packets.

    Out Data

    (None)

    Reply Data

    int fieldIDSize fieldID size in bytes  
    int methodIDSize methodID size in bytes  
    int objectIDSize objectID size in bytes  
    int referenceTypeIDSize referenceTypeID size in bytes  
    int frameIDSize frameID size in bytes  

    Error Data

    VM_DEAD The virtual machine is not running.
    Suspend Command (8)
    Suspends the execution of the application running in the target VM. All Java threads currently running will be suspended.

    Unlike java.lang.Thread.suspend, suspends of both the virtual machine and individual threads are counted. Before a thread will run again, it must be resumed through the VM-level resume command or the thread-level resume command the same number of times it has been suspended.

    Out Data

    (None)

    Reply Data

    (None)

    Error Data

    VM_DEAD The virtual machine is not running.
    Resume Command (9)
    Resumes execution of the application after the suspend command or an event has stopped it. Suspensions of the Virtual Machine and individual threads are counted. If a particular thread is suspended n times, it must resumed n times before it will continue.

    Out Data

    (None)

    Reply Data

    (None)

    Error Data

    (None)
    Exit Command (10)
    Terminates the target VM with the given exit code. All ids previously returned from the target VM become invalid. Threads running in the VM are abruptly terminated. A thread death exception is not thrown and finally blocks are not run.

    Out Data

    int exitCode the exit code 

    Reply Data

    (None)

    Error Data

    (None)
    CreateString Command (11)
    Creates a new string object in the target VM and returns its id.

    Out Data

    string utf UTF-8 characters to use in the created string.  

    Reply Data

    stringID stringObject Created string (instance of java.lang.String)  

    Error Data

    VM_DEAD The virtual machine is not running.
    Capabilities Command (12)
    Retrieve this VM's capabilities. The capabilities are returned as booleans, each indicating the presence or absence of a capability. The commands associated with each capability will return the NOT_IMPLEMENTED error if the cabability is not available.

    Out Data

    (None)

    Reply Data

    boolean canWatchFieldModification Can the VM watch field modification, and therefore can it send the Modification Watchpoint Event? 
    boolean canWatchFieldAccess Can the VM watch field access, and therefore can it send the Access Watchpoint Event? 
    boolean canGetBytecodes Can the VM get the bytecodes of a given method?  
    boolean canGetSyntheticAttribute Can the VM determine whether a field or method is synthetic? (that is, can the VM determine if the method or the field was invented by the compiler?)  
    boolean canGetOwnedMonitorInfo Can the VM get the owned monitors infornation for a thread? 
    boolean canGetCurrentContendedMonitor Can the VM get the current contended monitor of a thread? 
    boolean canGetMonitorInfo Can the VM get the monitor information for a given object?  

    Error Data

    VM_DEAD The virtual machine is not running.
    ClassPaths Command (13)
    Retrieve the classpath and bootclasspath of the target VM. If the classpath is not defined, returns an empty list. If the bootclasspath is not defined returns an empty list.

    Out Data

    (None)

    Reply Data

    string baseDir Base directory used to resolve relative paths in either of the following lists. 
    int classpaths Number of paths in classpath. 
    Repeated classpaths times:
    string path One component of classpath 
    int bootclasspaths Number of paths in bootclasspath. 
    Repeated bootclasspaths times:
    string path One component of bootclasspath 

    Error Data

    VM_DEAD The virtual machine is not running.
    DisposeObjects Command (14)
    Releases a list of object IDs. For each object in the list, the following applies. The count of references held by the back-end (the reference count) will be decremented by refCnt. If thereafter the reference count is less than or equal to zero, the ID is freed. Any back-end resources associated with the freed ID may be freed, and if garbage collection was disabled for the object, it will be re-enabled. The sender of this command promises that no further commands will be sent referencing a freed ID.

    Use of this command is not required. If it is not sent, resources associated with each ID will be freed by the back-end at some time after the corresponding object is garbage collected. It is most useful to use this command to reduce the load on the back-end if a very large number of objects has been retrieved from the back-end (a large array, for example) but may not be garbage collected any time soon.

    IDs may be re-used by the back-end after they have been freed with this command.This description assumes reference counting, a back-end may use any implementation which operates equivalently.

    Out Data

    int requests Number of object dispose requests that follow 
    Repeated requests times:
    objectID object The object ID 
    int refCnt The number of times this object ID has been part of a packet received from the back-end. An accurate count prevents the object ID from being freed on the back-end if it is part of an incoming packet, not yet handled by the front-end. 

    Reply Data

    (None)

    Error Data

    (None)
    HoldEvents Command (15)
    Tells the target VM to stop sending events. Events are not discarded; they are held until a subsequent ReleaseEvents command is sent. This command is useful to control the number of events sent to the debugger VM in situations where very large numbers of events are generated. While events are held by the debugger back-end, application execution may be frozen by the debugger back-end to prevent buffer overflows on the back end. Responses to commands are never held and are not affected by this command. If events are already being held, this command is ignored.

    Out Data

    (None)

    Reply Data

    (None)

    Error Data

    (None)
    ReleaseEvents Command (16)
    Tells the target VM to continue sending events. This command is used to restore normal activity after a HoldEvents command. If there is no current HoldEvents command in effect, this command is ignored.

    Out Data

    (None)

    Reply Data

    (None)

    Error Data

    (None)
    CapabilitiesNew Command (17)
    Retrieve all of this VM's capabilities. The capabilities are returned as booleans, each indicating the presence or absence of a capability. The commands associated with each capability will return the NOT_IMPLEMENTED error if the cabability is not available.Since JDWP version 1.4.

    Out Data

    (None)

    Reply Data

    boolean canWatchFieldModification Can the VM watch field modification, and therefore can it send the Modification Watchpoint Event? 
    boolean canWatchFieldAccess Can the VM watch field access, and therefore can it send the Access Watchpoint Event? 
    boolean canGetBytecodes Can the VM get the bytecodes of a given method?  
    boolean canGetSyntheticAttribute Can the VM determine whether a field or method is synthetic? (that is, can the VM determine if the method or the field was invented by the compiler?)  
    boolean canGetOwnedMonitorInfo Can the VM get the owned monitors infornation for a thread? 
    boolean canGetCurrentContendedMonitor Can the VM get the current contended monitor of a thread? 
    boolean canGetMonitorInfo Can the VM get the monitor information for a given object?  
    boolean canRedefineClasses Can the VM redefine classes? 
    boolean canAddMethod Can the VM add methods when redefining classes? 
    boolean canUnrestrictedlyRedefineClasses Can the VM redefine classesin arbitrary ways? 
    boolean canPopFrames Can the VM pop stack frames? 
    boolean canUseInstanceFilters Can the VM filter events by specific object? 
    boolean canGetSourceDebugExtension Can the VM get the source debug extension? 
    boolean canRequestVMDeathEvent Can the VM request VM death events? 
    boolean canSetDefaultStratum Can the VM set a default stratum? 
    boolean reserved16 Reserved for future capability 
    boolean reserved17 Reserved for future capability 
    boolean reserved18 Reserved for future capability 
    boolean reserved19 Reserved for future capability 
    boolean reserved20 Reserved for future capability 
    boolean reserved21 Reserved for future capability 
    boolean reserved22 Reserved for future capability 
    boolean reserved23 Reserved for future capability 
    boolean reserved24 Reserved for future capability 
    boolean reserved25 Reserved for future capability 
    boolean reserved26 Reserved for future capability 
    boolean reserved27 Reserved for future capability 
    boolean reserved28 Reserved for future capability 
    boolean reserved29 Reserved for future capability 
    boolean reserved30 Reserved for future capability 
    boolean reserved31 Reserved for future capability 
    boolean reserved32 Reserved for future capability 

    Error Data

    VM_DEAD The virtual machine is not running.
    RedefineClasses Command (18)
    Installs new class definitions.

    Out Data

    int classes Number of reference types that follow. 
    Repeated classes times:
    referenceTypeID refType The reference type. 
    int classfile  
    Repeated classfile times:
    byte classbyte byte in JVM class file format. 

    Reply Data

    (None)

    Error Data

    INVALID_CLASS One of the refType is not the ID of a reference type.
    INVALID_OBJECT One of the refType is not a known ID.
    UNSUPPORTED_VERSION A class file has a version number not supported by this VM.
    INVALID_CLASS_FORMAT The virtual machine attempted to read a class file and determined that the file is malformed or otherwise cannot be interpreted as a class file.
    CIRCULAR_CLASS_DEFINITION A circularity has been detected while initializing a class.
    FAILS_VERIFICATION The verifier detected that a class file, though well formed, contained some sort of internal inconsistency or security problem.
    NAMES_DONT_MATCH The class name defined in the new class file is different from the name in the old class object.
    NOT_IMPLEMENTED No aspect of this functionality is implemented (CapabilitiesNew.canRedefineClasses is false)
    ADD_METHOD_NOT_IMPLEMENTED Adding methods has not been implemented.
    SCHEMA_CHANGE_NOT_IMPLEMENTED Schema change has not been implemented.
    HIERARCHY_CHANGE_NOT_IMPLEMENTED A direct superclass is different for the new class version, or the set of directly implemented interfaces is different and canUnrestrictedlyRedefineClasses is false.
    DELETE_METHOD_NOT_IMPLEMENTED The new class version does not declare a method declared in the old class version and canUnrestrictedlyRedefineClasses is false.
    CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTED The new class version has different modifiers and and canUnrestrictedlyRedefineClasses is false.
    METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTED A method in the new class version has different modifiers than its counterpart in the old class version and and canUnrestrictedlyRedefineClasses is false.
    VM_DEAD The virtual machine is not running.
    SetDefaultStratum Command (19)
    Set the default stratum.

    Out Data

    string stratumID default stratum, or empty string to use reference type default. 

    Reply Data

    (None)

    Error Data

    NOT_IMPLEMENTED The functionality is not implemented in this virtual machine.
    VM_DEAD The virtual machine is not running.

    ReferenceType Command Set (2)

    Signature Command (1)
    Returns the JNI signature of a reference type. JNI signature formats are described in the Java Native Inteface Specification

    For primitive classes the returned signature is the signature of the corresponding primitive type; for example, "I" is returned as the signature of the class represented by java.lang.Integer.TYPE.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    string signature The JNI signature for the reference type. 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    ClassLoader Command (2)
    Returns the instance of java.lang.ClassLoader which loaded a given reference type. If the reference type was loaded by the system class loader, the returned object ID is null.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    classLoaderID classLoader The class loader for the reference type.  

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    Modifiers Command (3)
    Returns the modifiers (also known as access flags) for a reference type. The returned bit mask contains information on the declaration of the reference type. If the reference type is an array or a primitive class (for example, java.lang.Integer.TYPE), the value of the returned bit mask is undefined.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int modBits Modifier bits as defined in the VM Specification 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    Fields Command (4)
    Returns information for each field in a reference type. Inherited fields are not included. The field list will include any synthetic fields created by the compiler. Fields are returned in the order they occur in the class file.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int declared Number of declared fields. 
    Repeated declared times:
    fieldID fieldID Field ID. 
    string name Name of field. 
    string signature top>JNI Signature of field. 
    int modBits The modifier bit flags (also known as access flags) which provide additional information on the field declaration. Individual flag values are defined in the VM Specification.In addition, The 0xf0000000 bit identifies the field as synthetic, if the synthetic attribute capability is available. 

    Error Data

    CLASS_NOT_PREPARED Class has been loaded but not yet prepared.
    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    Methods Command (5)
    Returns information for each method in a reference type. Inherited methodss are not included. The list of methods will include constructors (identified with the name "<init>"), the initialization method (identified with the name "<clinit>") if present, and any synthetic methods created by the compiler. Methods are returned in the order they occur in the class file.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int declared Number of declared methods. 
    Repeated declared times:
    methodID methodID Method ID. 
    string name Name of method. 
    string signature top>JNI signature of method. 
    int modBits The modifier bit flags (also known as access flags) which provide additional information on the method declaration. Individual flag values are defined in the VM Specification.In addition, The 0xf0000000 bit identifies the method as synthetic, if the synthetic attribute capability is available. 

    Error Data

    CLASS_NOT_PREPARED Class has been loaded but not yet prepared.
    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    GetValues Command (6)
    Returns the value of one or more static fields of the reference type. Each field must be member of the reference type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be obtained.

    Out Data

    referenceTypeID refType The reference type ID. 
    int fields The number of values to get 
    Repeated fields times:
    fieldID fieldID A field to get 

    Reply Data

    int values The number of values returned 
    Repeated values times:
    value value The field value 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    INVALID_FIELDID Invalid field.
    VM_DEAD The virtual machine is not running.
    SourceFile Command (7)
    Returns the name of source file in which a reference type was declared.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    string sourceFile The source file name. No path information for the file is included 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    NestedTypes Command (8)
    Returns the classes and interfaces directly nested within this type.Types further nested within those types are not included.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int classes The number of nested classes and interfaces 
    Repeated classes times:
    byte refTypeTag Kind of following reference type.  
    referenceTypeID typeID The nested class or interface ID. 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    Status Command (9)
    Returns the current status of the reference type. The status indicates the extent to which the reference type has been initialized, as described in the VM specification. The returned status bits are undefined for array types and for primitive classes (such as java.lang.Integer.TYPE).

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int status Status bits:See JDWP.ClassStatus 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    Interfaces Command (10)
    Returns the interfaces declared as implemented by this class. Interfaces indirectly implemented (extended by the implemented interface or implemented by a superclass) are not included.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    int interfaces The number of implemented interfaces 
    Repeated interfaces times:
    interfaceID interfaceType implemented interface. 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    ClassObject Command (11)
    Returns the class object corresponding to this type.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    classObjectID classObject class object. 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    VM_DEAD The virtual machine is not running.
    SourceDebugExtension Command (12)
    Returns the value of the SourceDebugExtension attribute. Since JDWP version 1.4.

    Out Data

    referenceTypeID refType The reference type ID. 

    Reply Data

    string extension extension attribute 

    Error Data

    INVALID_CLASS refType is not the ID of a reference type.
    INVALID_OBJECT refType is not a known ID.
    ABSENT_INFORMATION If the extension is not specified.
    NOT_IMPLEMENTED The functionality is not implemented in this virtual machine.
    VM_DEAD The virtual machine is not running.

    ClassType Command Set (3)

    Superclass Command (1)
    Returns the immediate superclass of a class.

    Out Data

    classID clazz The class type ID. 

    Reply Data

    classID superclass The superclass (null if the class ID for java.lang.Object is specified). 

    Error Data

    INVALID_CLASS clazz is not the ID of a class.
    INVALID_OBJECT clazz is not a known ID.
    VM_DEAD The virtual machine is not running.
    SetValues Command (2)
    Sets the value of one or more static fields. Each field must be member of the class type or one of its superclasses, superinterfaces, or implemented interfaces. Access control is not enforced; for example, the values of private fields can be set. Final fields cannot be set.For primitive values, the value's type must match the field's type exactly. For object values, there must exist a widening reference conversion from the value's type to the field's type and the field's type must be loaded.

    Out Data

    classID clazz The class type ID. 
    int values The number of fields to set. 
    Repeated values times:
    fieldID fieldID Field to s