Java Debug Interface

com.sun.jdi
Interface ReferenceType

All Superinterfaces:
Accessible, Comparable<ReferenceType>, Mirror, Type
All Known Subinterfaces:
ArrayType, ClassType, InterfaceType

public interface ReferenceType
extends Type, Comparable<ReferenceType>, Accessible

The type of an object in a target VM. ReferenceType encompasses classes, interfaces, and array types as defined in the JavaTM Language Specification. All ReferenceType objects belong to one of the following subinterfaces: ClassType for classes, InterfaceType for interfaces, and ArrayType for arrays. Note that primitive classes (for example, the reflected type of Integer.TYPE) are represented as ClassType. The VM creates Class objects for all three, so from the VM perspective, each ReferenceType maps to a distinct Class object.

ReferenceTypes can be obtained by querying a particular ObjectReference for its type or by getting a list of all reference types from the VirtualMachine.

ReferenceType provides access to static type information such as methods and fields and provides access to dynamic type information such as the corresponding Class object and the classloader.

Any method on ReferenceType which directly or indirectly takes ReferenceType 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 ReferenceType which directly or indirectly takes ReferenceType as an parameter may throw VMOutOfMemoryException if the target VM has run out of memory.

Any method on ReferenceType or which directly or indirectly takes ReferenceType as parameter may throw ObjectCollectedException if the mirrored type has been unloaded.

Since:
1.3
See Also:
ObjectReference, ObjectReference.referenceType(), VirtualMachine, VirtualMachine.allClasses()

Method Summary
 List<Field> allFields()
          Returns a list containing each Field declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces.
 List<Location> allLineLocations()
          Returns a list containing a Location object for each executable source line in this reference type.
 List<Location> allLineLocations(String stratum, String sourceName)
          Returns a list containing a Location object for each executable source line in this reference type.
 List<Method> allMethods()
          Returns a list containing each Method declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces.
 List<String> availableStrata()
          Return the available strata for this reference type.
 ClassLoaderReference classLoader()
          Gets the classloader object which loaded the class corresponding to this type.
 ClassObjectReference classObject()
          Returns the class object that corresponds to this type in the target VM.
 byte[] constantPool()
          Returns the raw bytes of the constant pool in the format of the constant_pool item of the Class File Format in the Java Virtual Machine Specification.
 int constantPoolCount()
          Returns the number of entries in the constant pool plus one.
 String defaultStratum()
          Returns the default stratum for this reference type.
 boolean equals(Object obj)
          Compares the specified Object with this ReferenceType for equality.
 boolean failedToInitialize()
          Determines if initialization failed for this class.
 Field fieldByName(String fieldName)
          Finds the visible Field with the given non-ambiguous name.
 List<Field> fields()
          Returns a list containing each Field declared in this type.
 String genericSignature()
          Gets the generic signature for this type if there is one.
 Value getValue(Field field)
          Gets the Value of a given static Field in this type.
 Map<Field,Value> getValues(List<? extends Field> fields)
          Returns a map containing the Value of each static Field in the given list.
 int hashCode()
          Returns the hash code value for this ObjectReference.
 List<ObjectReference> instances(long maxInstances)
          Returns instances of this ReferenceType.
 boolean isAbstract()
          Determines if this type was declared abstract.
 boolean isFinal()
          Determines if this type was declared final.
 boolean isInitialized()
          Determines if this type has been initialized.
 boolean isPrepared()
          Determines if this type has been prepared.
 boolean isStatic()
          Determines if this type was declared static.
 boolean isVerified()
          Determines if this type has been verified.
 List<Location> locationsOfLine(int lineNumber)
          Returns a List containing all Location objects that map to the given line number.
 List<Location> locationsOfLine(String stratum, String sourceName, int lineNumber)
          Returns a List containing all Location objects that map to the given line number.
 int majorVersion()
          Returns the class major version number, as defined in the class file format of the Java Virtual Machine Specification.
 List<Method> methods()
          Returns a list containing each Method declared directly in this type.
 List<Method> methodsByName(String name)
          Returns a List containing each visible Method that has the given name.
 List<Method> methodsByName(String name, String signature)
          Returns a List containing each visible Method that has the given name and signature.
 int minorVersion()
          Returns the class minor version number, as defined in the class file format of the Java Virtual Machine Specification.
 String name()
          Gets the fully qualified name of this type.
 List<ReferenceType> nestedTypes()
          Returns a List containing ReferenceType objects that are declared within this type and are currently loaded into the Virtual Machine.
 String sourceDebugExtension()
          Get the source debug extension of this type.
 String sourceName()
          Gets an identifying name for the source corresponding to the declaration of this type.
 List<String> sourceNames(String stratum)
          Gets the identifying names for all the source corresponding to the declaration of this type.
 List<String> sourcePaths(String stratum)
          Gets the paths to the source corresponding to the declaration of this type.
 List<Field> visibleFields()
          Returns a list containing each unhidden and unambiguous Field in this type.
 List<Method> visibleMethods()
          Returns a list containing each Method declared or inherited by this type.
 
Methods inherited from interface com.sun.jdi.Type
signature
 
Methods inherited from interface com.sun.jdi.Mirror
toString, virtualMachine
 
Methods inherited from interface java.lang.Comparable
compareTo
 
Methods inherited from interface com.sun.jdi.Accessible
isPackagePrivate, isPrivate, isProtected, isPublic, modifiers
 

Method Detail

name

String name()
Gets the fully qualified name of this type. The returned name is formatted as it might appear in a Java programming langauge declaration for objects of this type.

For primitive classes the returned name is the name of the corresponding primitive type; for example, "int" is returned as the name of the class represented by Integer.TYPE.

Specified by:
name in interface Type
Returns:
a string containing the type name.

genericSignature

String genericSignature()
Gets the generic signature for this type if there is one. Generic signatures are described in the "JavaTM Virtual Machine Specification, 3rd Edition.

Returns:
a string containing the generic signature, or null if there is no generic signature.
Since:
1.5

classLoader

ClassLoaderReference classLoader()
Gets the classloader object which loaded the class corresponding to this type.

Returns:
a ClassLoaderReference which mirrors the classloader, or null if the class was loaded through the bootstrap class loader.

sourceName

String sourceName()
                  throws AbsentInformationException
Gets an identifying name for the source corresponding to the declaration of this type. Interpretation of this string is the responsibility of the source repository mechanism.

The returned name is dependent on VM's default stratum (VirtualMachine.getDefaultStratum()). In the reference implementation, when using the base stratum, the returned string is the unqualified name of the source file containing the declaration of this type. In other strata the returned source name is the first source name for that stratum. Since other languages may have more than one source name for a reference type, the use of Location.sourceName() or sourceNames(String) is preferred.

For arrays (ArrayType) and primitive classes, AbsentInformationException is always thrown.

Returns:
the string source file name
Throws:
AbsentInformationException - if the source name is not known

sourceNames

List<String> sourceNames(String stratum)
                         throws AbsentInformationException
Gets the identifying names for all the source corresponding to the declaration of this type. Interpretation of these names is the responsibility of the source repository mechanism.

The returned names are for the specified stratum (see Location for a description of strata). In the reference implementation, when using the Java programming language stratum, the returned List contains one element: a String which is the unqualified name of the source file containing the declaration of this type. In other strata the returned source names are all the source names defined for that stratum.

Parameters:
stratum - The stratum to retrieve information from or null for the declaring type's default stratum.
Returns:
a List of String objects each representing a source name
Throws:
AbsentInformationException - if the source names are not known.

For arrays (ArrayType) and primitive classes, AbsentInformationException is always thrown.

Since:
1.4

sourcePaths

List<String> sourcePaths(String stratum)
                         throws AbsentInformationException
Gets the paths to the source corresponding to the declaration of this type. Interpretation of these paths is the responsibility of the source repository mechanism.

The returned paths are for the specified stratum (see Location for a description of strata). In the reference implementation, for strata which do not explicitly specify source path (the Java programming language stratum never does), the returned strings are the sourceNames(String) prefixed by the package name of this ReferenceType converted to a platform dependent path. For example, on a Windows platform, java.lang.Thread would return a List containing one element: "java\lang\Thread.java".

Parameters:
stratum - The stratum to retrieve information from or null for the declaring type's default stratum.
Returns:
a List of String objects each representing a source path
Throws:
AbsentInformationException - if the source names are not known.

For arrays (ArrayType) and primitive classes, AbsentInformationException is always thrown.

Since:
1.4

sourceDebugExtension

String sourceDebugExtension()
                            throws AbsentInformationException
Get the source debug extension of this type.

Not all target virtual machines support this operation. Use canGetSourceDebugExtension() to determine if the operation is supported.

Returns:
as a string the source debug extension attribute
Throws:
AbsentInformationException - if the extension is not specified
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetSourceDebugExtension(),

isStatic

boolean isStatic()
Determines if this type was declared static. Only nested types, can be declared static, so false is returned for any package-level type, array type, or primitive class.

Returns:
true if this type is static; false otherwise.

isAbstract

boolean isAbstract()
Determines if this type was declared abstract.

For arrays (ArrayType) and primitive classes, the return value is undefined.

Returns:
true if this type is abstract; false otherwise.

isFinal

boolean isFinal()
Determines if this type was declared final.

For arrays (ArrayType) and primitive classes, the return value is always true.

Returns:
true if this type is final; false otherwise.

isPrepared

boolean isPrepared()
Determines if this type has been prepared. See the JVM specification for a definition of class preparation.

For arrays (ArrayType) and primitive classes, the return value is undefined.

Returns:
true if this type is prepared; false otherwise.

isVerified

boolean isVerified()
Determines if this type has been verified. See the JVM specification for a definition of class verification.

For arrays (ArrayType) and primitive classes, the return value is undefined.

Returns:
true if this type is verified; false otherwise.

isInitialized

boolean isInitialized()
Determines if this type has been initialized. See the JVM specification for a definition of class verification. For InterfaceType, this method always returns the same value as isPrepared().

For arrays (ArrayType) and primitive classes, the return value is undefined.

Returns:
true if this type is initialized; false otherwise.

failedToInitialize

boolean failedToInitialize()
Determines if initialization failed for this class. See the JVM specification for details on class initialization.

For arrays (ArrayType) and primitive classes, the return value is undefined.

Returns:
true if initialization was attempted and failed; false otherwise.

fields

List<Field> fields()
Returns a list containing each Field declared in this type. Inherited fields are not included. Any synthetic fields created by the compiler are included in the list.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a list Field objects; the list has length 0 if no fields exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

visibleFields

List<Field> visibleFields()
Returns a list containing each unhidden and unambiguous Field in this type. Each field that can be accessed from the class or its instances with its simple name is included. Fields that are ambiguously multiply inherited or fields that are hidden by fields with the same name in a more recently inherited class cannot be accessed by their simple names and are not included in the returned list. All other inherited fields are included. See JLS section 8.3 for details.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a List of Field objects; the list has length 0 if no visible fields exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

allFields

List<Field> allFields()
Returns a list containing each Field declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces. All declared and inherited fields are included, regardless of whether they are hidden or multiply inherited.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a List of Field objects; the list has length 0 if no fields exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

fieldByName

Field fieldByName(String fieldName)
Finds the visible Field with the given non-ambiguous name. This method follows the inheritance rules specified in the JLS (8.3.3) to determine visibility.

For arrays (ArrayType) and primitive classes, the returned value is always null.

Parameters:
fieldName - a String containing the name of desired field.
Returns:
a Field object which mirrors the found field, or null if there is no field with the given name or if the given name is ambiguous.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

methods

List<Method> methods()
Returns a list containing each Method declared directly in this type. Inherited methods are not included. Constructors, the initialization method if any, and any synthetic methods created by the compiler are included in the list.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a list Method objects; the list has length 0 if no methods exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

visibleMethods

List<Method> visibleMethods()
Returns a list containing each Method declared or inherited by this type. Methods from superclasses or superinterfaces that that have been hidden or overridden are not included.

Note that despite this exclusion, multiple inherited methods with the same signature can be present in the returned list, but at most one can be a member of a ClassType. See JLS section 8.4.6 for details.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a List of Method objects; the list has length 0 if no visible methods exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

allMethods

List<Method> allMethods()
Returns a list containing each Method declared in this type, and its superclasses, implemented interfaces, and/or superinterfaces. All declared and inherited methods are included, regardless of whether they are hidden or overridden.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a List of Method objects; the list has length 0 if no methods exist.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

methodsByName

List<Method> methodsByName(String name)
Returns a List containing each visible Method that has the given name. This is most commonly used to find overloaded methods.

Overridden and hidden methods are not included. See JLS (8.4.6) for details.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Parameters:
name - the name of the method to find.
Returns:
a List of Method objects that match the given name; the list has length 0 if no matching methods are found.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

methodsByName

List<Method> methodsByName(String name,
                           String signature)
Returns a List containing each visible Method that has the given name and signature. The signature string is the JNI signature for the target method: This method follows the inheritance rules specified in the JLS (8.4.6) to determine visibility.

At most one method in the list is a concrete method and a component of ClassType; any other methods in the list are abstract. Use ClassType.concreteMethodByName(java.lang.String, java.lang.String) to retrieve only the matching concrete method.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Parameters:
name - the name of the method to find.
signature - the signature of the method to find
Returns:
a List of Method objects that match the given name and signature; the list has length 0 if no matching methods are found.
Throws:
ClassNotPreparedException - if this class not yet been prepared.

nestedTypes

List<ReferenceType> nestedTypes()
Returns a List containing ReferenceType objects that are declared within this type and are currently loaded into the Virtual Machine. Both static nested types and non-static nested types (that is, inner types) are included. Local inner types (declared within a code block somewhere in this reference type) are also included in the returned list.

For arrays (ArrayType) and primitive classes, the returned list is always empty.

Returns:
a List of nested ReferenceType objects; the list has 0 length if there are no nested types.

getValue

Value getValue(Field field)
Gets the Value of a given static Field in this type. The Field must be valid for this type; that is, it must be declared in this type, a superclass, a superinterface, or an implemented interface.

Parameters:
field - the field containing the requested value
Returns:
the Value of the instance field.
Throws:
IllegalArgumentException - if the field is not valid for this object's class.

getValues

Map<Field,Value> getValues(List<? extends Field> fields)
Returns a map containing the Value of each static Field in the given list. The Fields must be valid for this type; that is, they must be declared in this type, a superclass, a superinterface, or an implemented interface.

Parameters:
fields - a list of Field objects containing the requested values.
Returns:
a Map of the requested Field objects with their Value.
Throws:
IllegalArgumentException - if any field is not valid for this object's class.
VMMismatchException - if a Mirror argument and this mirror do not belong to the same VirtualMachine.

classObject

ClassObjectReference classObject()
Returns the class object that corresponds to this type in the target VM. The VM creates class objects for every kind of ReferenceType: classes, interfaces, and array types.

Returns:
the ClassObjectReference for this reference type in the target VM.

allLineLocations

List<Location> allLineLocations()
                                throws AbsentInformationException
Returns a list containing a Location object for each executable source line in this reference type.

This method is equivalent to allLineLocations(vm.getDefaultStratum(),null) - see allLineLocations(String,String) for more information.

Throws:
AbsentInformationException - if there is no line number information for this class and there are non-native, non-abstract executable members of this class.
ClassNotPreparedException - if this class not yet been prepared.

allLineLocations

List<Location> allLineLocations(String stratum,
                                String sourceName)
                                throws AbsentInformationException
Returns a list containing a Location object for each executable source line in this reference type. Each location maps a source line to a range of code indices. The beginning of the range can be determined through Location.codeIndex(). The returned list may contain multiple locations for a particular line number, if the compiler and/or VM has mapped that line to two or more disjoint code index ranges. Note that it is possible for the same source line to represent different code index ranges in different methods.

For arrays (ArrayType) and primitive classes, the returned list is always empty. For interfaces (InterfaceType), the returned list will be non-empty only if the interface has executable code in its class initialization.

Returned list is for the specified stratum (see Location for a description of strata).

Parameters:
stratum - The stratum to retrieve information from or null for the defaultStratum().
sourceName - Return locations only within this source file or null to return locations.
Returns:
a List of all source line Location objects.
Throws:
AbsentInformationException - if there is no line number information for this class and there are non-native, non-abstract executable members of this class. Or if sourceName is non-null and source name information is not present.
ClassNotPreparedException - if this class not yet been prepared.
Since:
1.4

locationsOfLine

List<Location> locationsOfLine(int lineNumber)
                               throws AbsentInformationException
Returns a List containing all Location objects that map to the given line number.

This method is equivalent to locationsOfLine(vm.getDefaultStratum(), null, lineNumber) - see locationsOfLine(java.lang.String,java.lang.String,int) for more information.

Parameters:
lineNumber - the line number
Returns:
a List of all Location objects that map to the given line.
Throws:
AbsentInformationException - if there is no line number information for this class.
ClassNotPreparedException - if this class not yet been prepared.
See Also:
VirtualMachine.getDefaultStratum()

locationsOfLine

List<Location> locationsOfLine(String stratum,
                               String sourceName,
                               int lineNumber)
                               throws AbsentInformationException
Returns a List containing all Location objects that map to the given line number.

For arrays (ArrayType) and primitive classes, the returned list is always empty. For interfaces (InterfaceType), the returned list will be non-empty only if the interface has executable code in its class initialization at the specified line number. An empty list will be returned if there is no executable code at the specified line number.

Returned list is for the specified stratum (see Location for a description of strata).

Parameters:
stratum - the stratum to use for comparing line number and source name, or null to use the defaultStratum().
sourceName - the source name containing the line number, or null to match all source names
lineNumber - the line number
Returns:
a List of all Location objects that map to the given line.
Throws:
AbsentInformationException - if there is no line number information for this class. Or if sourceName is non-null and source name information is not present.
ClassNotPreparedException - if this class not yet been prepared.
Since:
1.4

availableStrata

List<String> availableStrata()
Return the available strata for this reference type.

See the Location for a description of strata.

Returns:
List of java.lang.String, each representing a stratum
Since:
1.4

defaultStratum

String defaultStratum()
Returns the default stratum for this reference type. This value is specified in the class file and cannot be set by the user. If the class file does not specify a default stratum the base stratum ("Java") will be returned.

See the Location for a description of strata.

Since:
1.4

instances

List<ObjectReference> instances(long maxInstances)
Returns instances of this ReferenceType. Only instances that are reachable for the purposes of garbage collection are returned.

Not all target virtual machines support this operation. Use VirtualMachine.canGetInstanceInfo() to determine if the operation is supported.

Parameters:
maxInstances - the maximum number of instances to return. Must be non-negative. If zero, all instances are returned.
Returns:
a List of ObjectReference objects. If there are no instances of this ReferenceType, a zero-length list is returned.
Throws:
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetInstanceInfo()
IllegalArgumentException - if maxInstances is less than zero.
Since:
1.6
See Also:
VirtualMachine.instanceCounts(List), ObjectReference.referringObjects(long)

equals

boolean equals(Object obj)
Compares the specified Object with this ReferenceType for equality.

Overrides:
equals in class Object
Returns:
true if the Object is a ReferenceType, if the ReferenceTypes belong to the same VM, and if they mirror classes which correspond to the same instance of java.lang.Class in that VM.

hashCode

int hashCode()
Returns the hash code value for this ObjectReference.

Overrides:
hashCode in class Object
Returns:
the integer hash code

majorVersion

int majorVersion()
Returns the class major version number, as defined in the class file format of the Java Virtual Machine Specification. For arrays (ArrayType) and primitive classes, the returned major version number value is zero. Not all target virtual machines support this operation. Use VirtualMachine.canGetClassFileVersion() to determine if the operation is supported.

Returns:
the major version number of the class.
Throws:
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetClassFileVersion()
Since:
1.6

minorVersion

int minorVersion()
Returns the class minor version number, as defined in the class file format of the Java Virtual Machine Specification. For arrays (ArrayType) and primitive classes, the returned minor version number value is zero. Not all target virtual machines support this operation. Use VirtualMachine.canGetClassFileVersion() to determine if the operation is supported.

Returns:
the minor version number of the class.
Throws:
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetClassFileVersion()
Since:
1.6

constantPoolCount

int constantPoolCount()
Returns the number of entries in the constant pool plus one. This corresponds to the constant_pool_count item of the Class File Format in the Java Virtual Machine Specification. For arrays (ArrayType) and primitive classes, the returned constant pool count value is zero. Not all target virtual machines support this operation. Use VirtualMachine.canGetConstantPool() to determine if the operation is supported.

Returns:
total number of constant pool entries for a class plus one.
Throws:
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetConstantPool()
Since:
1.6
See Also:
constantPool()

constantPool

byte[] constantPool()
Returns the raw bytes of the constant pool in the format of the constant_pool item of the Class File Format in the Java Virtual Machine Specification. The format of the constant pool may differ between versions of the Class File Format, so, the minor and major class version numbers should be checked for compatibility. For arrays (ArrayType) and primitive classes, a zero length byte array is returned. Not all target virtual machines support this operation. Use VirtualMachine.canGetConstantPool() to determine if the operation is supported.

Returns:
the raw bytes of constant pool.
Throws:
UnsupportedOperationException - if the target virtual machine does not support this operation - see canGetConstantPool()
Since:
1.6
See Also:
constantPoolCount()

Java Debug Interface

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