javacard.framework
Class JCSystem

java.lang.Object
  javacard.framework.JCSystem

public final class JCSystem

extends Object

The JCSystem class includes a collection of methods to control applet execution, resource management, atomic transaction management, object deletion mechanism and inter-applet object sharing in the Java Card environment. All methods in JCSystem class are static methods.

This class also includes methods to control the persistence and transience of objects. The term persistent means that objects and their values persist from one CAD session to the next, indefinitely. Persistent object values are updated atomically using transactions.

The makeTransient...Array() methods can be used to create transient arrays. Transient array data is lost (in an undefined state, but the real data is unavailable) immediately upon power loss, and is reset to the default value at the occurrence of certain events such as card reset or deselect. Updates to the values of transient arrays are not atomic and are not affected by transactions.

The Java Card runtime environment maintains an atomic transaction commit buffer which is initialized on card reset (or power on). When a transaction is in progress, the Java Card runtime environment journals all updates to persistent data space into this buffer so that it can always guarantee, at commit time, that everything in the buffer is written or nothing at all is written. The JCSystem includes methods to control an atomic transaction. See Runtime Environment Specification for the Java Card Platform for details.

See Also:

SystemException

Field Summary

static byte	CLEAR_ON_DESELECT This event code indicates that the contents of the transient object are cleared to the default value on applet deselection event or in CLEAR_ON_RESET cases.
static byte	CLEAR_ON_RESET This event code indicates that the contents of the transient object are cleared to the default value on card reset (or power on) event.
static byte	MEMORY_TYPE_PERSISTENT Constant to indicate persistent memory type.
static byte	MEMORY_TYPE_TRANSIENT_DESELECT Constant to indicate transient memory of CLEAR_ON_DESELECT type.
static byte	MEMORY_TYPE_TRANSIENT_RESET Constant to indicate transient memory of CLEAR_ON_RESET type.
static byte	NOT_A_TRANSIENT_OBJECT This event code indicates that the object is not transient.

Method Summary

static void	abortTransaction() Aborts the atomic transaction.
static void	beginTransaction() Begins an atomic transaction.
static void	commitTransaction() Commits an atomic transaction.
static AID	getAID() Returns the Java Card runtime environment-owned instance of the AID object associated with the current applet context, or null if the Applet.register() method has not yet been invoked.
static Shareable	getAppletShareableInterfaceObject(AID serverAID, byte parameter) Called by a client applet to get a server applet's shareable interface object.
static byte	getAssignedChannel() This method is called to obtain the logical channel number assigned to the currently selected applet instance.
static short	getAvailableMemory(byte memoryType) Obtains the amount of memory of the specified type that is available to the applet.
static short	getMaxCommitCapacity() Returns the total number of bytes in the commit buffer.
static AID	getPreviousContextAID() Obtains the Java Card runtime environment-owned instance of the AID object associated with the previously active applet context.
static byte	getTransactionDepth() Returns the current transaction nesting depth level.
static short	getUnusedCommitCapacity() Returns the number of bytes left in the commit buffer.
static short	getVersion() Returns the current major and minor version of the Java Card API.
static boolean	isAppletActive(AID theApplet) This method is used to determine if the specified applet is active on the card.
static boolean	isObjectDeletionSupported() This method is used to determine if the implementation for the Java Card platform supports the object deletion mechanism.
static byte	isTransient(Object theObj) Checks if the specified object is transient.
static AID	lookupAID(byte[] buffer, short offset, byte length) Returns the Java Card runtime environment-owned instance of the AID object, if any, encapsulating the specified AID bytes in the buffer parameter if there exists a successfully installed applet on the card whose instance AID exactly matches that of the specified AID bytes.
static boolean[]	makeTransientBooleanArray(short length, byte event) Creates a transient boolean array with the specified array length.
static byte[]	makeTransientByteArray(short length, byte event) Creates a transient byte array with the specified array length.
static Object[]	makeTransientObjectArray(short length, byte event) Creates a transient array of Object with the specified array length.
static short[]	makeTransientShortArray(short length, byte event) Creates a transient short array with the specified array length.
static void	requestObjectDeletion() This method is invoked by the applet to trigger the object deletion service of the Java Card runtime environment.

Methods inherited from class java.lang.Object

equals

Field Detail

CLEAR_ON_RESET

public static final byte CLEAR_ON_RESET

This event code indicates that the contents of the transient object are cleared to the default value on card reset (or power on) event.

See Also:

Constant Field Values

NOT_A_TRANSIENT_OBJECT

public static final byte NOT_A_TRANSIENT_OBJECT

This event code indicates that the object is not transient.

See Also:

Constant Field Values

MEMORY_TYPE_TRANSIENT_RESET

public static final byte MEMORY_TYPE_TRANSIENT_RESET

Constant to indicate transient memory of CLEAR_ON_RESET type.

See Also:

Constant Field Values

CLEAR_ON_DESELECT

public static final byte CLEAR_ON_DESELECT

This event code indicates that the contents of the transient object are cleared to the default value on applet deselection event or in CLEAR_ON_RESET cases.

Notes:

• CLEAR_ON_DESELECT transient objects can be accessed only when the applet which created the object is in the same context as the currently selected applet.
• The Java Card runtime environment will throw a SecurityException if a CLEAR_ON_DESELECT transient object is accessed when the currently selected applet is not in the same context as the applet which created the object.

See Also:

Constant Field Values

MEMORY_TYPE_PERSISTENT

public static final byte MEMORY_TYPE_PERSISTENT

Constant to indicate persistent memory type.

See Also:

Constant Field Values

MEMORY_TYPE_TRANSIENT_DESELECT

public static final byte MEMORY_TYPE_TRANSIENT_DESELECT

Constant to indicate transient memory of CLEAR_ON_DESELECT type.

See Also:

Constant Field Values

Method Detail

getMaxCommitCapacity

public static short getMaxCommitCapacity()

Returns the total number of bytes in the commit buffer. This is approximately the maximum number of bytes of persistent data which can be modified during a transaction. However, the transaction subsystem requires additional bytes of overhead data to be included in the commit buffer, and this depends on the number of fields modified and the implementation of the transaction subsystem. The application cannot determine the actual maximum amount of data which can be modified during a transaction without taking these overhead bytes into consideration.

Note:

• If the total number of bytes in the commit buffer is greater than 32767, then this method returns 32767.

Returns:

the total number of bytes in the commit buffer

See Also:

getUnusedCommitCapacity()

getTransactionDepth

public static byte getTransactionDepth()

Returns the current transaction nesting depth level. At present, only 1 transaction can be in progress at a time.

Returns:

1 if transaction in progress, 0 if not

isAppletActive

public static boolean isAppletActive(AID theApplet)

This method is used to determine if the specified applet is active on the card.

Note:

• This method returns false if the specified applet is not active, even if its context is active.

Parameters:

theApplet - the AID of the applet object being queried

Returns:

true if and only if the applet specified by the AID parameter is currently active on this or another logical channel

See Also:

lookupAID(byte[], short, byte)

isTransient

public static byte isTransient(Object theObj)

Checks if the specified object is transient.

Note:

This method returns NOT_A_TRANSIENT_OBJECT if the specified object is null or is not an array type.

Parameters:

theObj - the object being queried

Returns:

NOT_A_TRANSIENT_OBJECT, CLEAR_ON_RESET, or CLEAR_ON_DESELECT

See Also:

makeTransientBooleanArray(short, byte)

getAID

public static AID getAID()

Returns the Java Card runtime environment-owned instance of the AID object associated with the current applet context, or null if the Applet.register() method has not yet been invoked.

Java Card runtime environment-owned instances of AID are permanent Java Card runtime environment Entry Point Objects and can be accessed from any applet context. References to these permanent objects can be stored and re-used.

See Runtime Environment Specification for the Java Card Platform, section 6.2.1 for details.

Returns:

the AID object

getUnusedCommitCapacity

public static short getUnusedCommitCapacity()

Returns the number of bytes left in the commit buffer.

Note:

• If the number of bytes left in the commit buffer is greater than 32767, then this method returns 32767.

Returns:

the number of bytes left in the commit buffer

See Also:

getMaxCommitCapacity()

requestObjectDeletion

public static void requestObjectDeletion()
                                  throws SystemException

This method is invoked by the applet to trigger the object deletion service of the Java Card runtime environment. If the Java Card runtime environment implements the object deletion mechanism, the request is merely logged at this time. The Java Card runtime environment must schedule the object deletion service prior to the next invocation of the Applet.process() method. The object deletion mechanism must ensure that :

• Any unreferenced persistent object owned by the current applet context is deleted and the associated space is recovered for reuse prior to the next invocation of the Applet.process() method.
• Any unreferenced CLEAR_ON_DESELECT or CLEAR_ON_RESET transient object owned by the current applet context is deleted and the associated space is recovered for reuse before the next card reset session.

Throws:

SystemException - with the following reason codes:

• SystemException.ILLEGAL_USE if the object deletion mechanism is not implemented.

makeTransientByteArray

public static byte[] makeTransientByteArray(short length,
                                            byte event)
                                     throws NegativeArraySizeException,
                                            SystemException

Creates a transient byte array with the specified array length.

Parameters:

length - the length of the byte array

event - the CLEAR_ON... event which causes the array elements to be cleared

Returns:

the new transient byte array

Throws:

NegativeArraySizeException - if the length parameter is negative

SystemException - with the following reason codes:

• SystemException.ILLEGAL_VALUE if event is not a valid event code.
• SystemException.NO_TRANSIENT_SPACE if sufficient transient space is not available.
• SystemException.ILLEGAL_TRANSIENT if the current applet context is not the currently selected applet context and CLEAR_ON_DESELECT is specified.

getAssignedChannel

public static byte getAssignedChannel()

This method is called to obtain the logical channel number assigned to the currently selected applet instance. The assigned logical channel is the logical channel on which the currently selected applet instance is or will be the active applet instance. This logical channel number is always equal to the origin logical channel number returned by the APDU.getCLAChannel() method except during selection and deselection via the MANAGE CHANNEL APDU command. If this method is called from the Applet.select(), Applet.deselect(), MultiSelectable.select(boolean) and MultiSelectable.deselect(boolean) methods during MANAGE CHANNEL APDU command processing, the logical channel number returned may be different.

Returns:

the logical channel number in the range 0-3 assigned to the currently selected applet instance

getVersion

public static short getVersion()

Returns the current major and minor version of the Java Card API.

Returns:

version number as byte.byte (major.minor)

commitTransaction

public static void commitTransaction()
                              throws TransactionException

Commits an atomic transaction. The contents of commit buffer is atomically committed. If a transaction is not in progress (transaction nesting depth level == 0) then a TransactionException is thrown.

Note:

• This method may do nothing if the Applet.register() method has not yet been invoked. In case of tear or failure prior to successful registration, the Java Card runtime environment will roll back all atomically updated persistent state.

Throws:

TransactionException - with the following reason codes:

• TransactionException.NOT_IN_PROGRESS if a transaction is not in progress.

See Also:

beginTransaction()

getPreviousContextAID

public static AID getPreviousContextAID()

Obtains the Java Card runtime environment-owned instance of the AID object associated with the previously active applet context. This method is typically used by a server applet, while executing a shareable interface method to determine the identity of its client and thereby control access privileges.

Java Card runtime environment-owned instances of AID are permanent Java Card runtime environment Entry Point Objects and can be accessed from any applet context. References to these permanent objects can be stored and re-used.

See Runtime Environment Specification for the Java Card Platform, section 6.2.1 for details.

Returns:

the AID object of the previous context, or null if Java Card runtime environment

isObjectDeletionSupported

public static boolean isObjectDeletionSupported()

This method is used to determine if the implementation for the Java Card platform supports the object deletion mechanism.

Returns:

true if the object deletion mechanism is supported, false otherwise

beginTransaction

public static void beginTransaction()
                             throws TransactionException

Begins an atomic transaction. If a transaction is already in progress (transaction nesting depth level != 0), a TransactionException is thrown.

Note:

• This method may do nothing if the Applet.register() method has not yet been invoked. In case of tear or failure prior to successful registration, the Java Card runtime environment will roll back all atomically updated persistent state.

Throws:

TransactionException - with the following reason codes:

• TransactionException.IN_PROGRESS if a transaction is already in progress.

See Also:

commitTransaction()

makeTransientBooleanArray

public static boolean[] makeTransientBooleanArray(short length,
                                                  byte event)
                                           throws NegativeArraySizeException,
                                                  SystemException

Creates a transient boolean array with the specified array length.

Parameters:

length - the length of the boolean array

event - the CLEAR_ON... event which causes the array elements to be cleared

Returns:

the new transient boolean array

Throws:

NegativeArraySizeException - if the length parameter is negative

SystemException - with the following reason codes:

• SystemException.ILLEGAL_VALUE if event is not a valid event code.
• SystemException.NO_TRANSIENT_SPACE if sufficient transient space is not available.
• SystemException.ILLEGAL_TRANSIENT if the current applet context is not the currently selected applet context and CLEAR_ON_DESELECT is specified.

getAvailableMemory

public static short getAvailableMemory(byte memoryType)
                                throws SystemException

Obtains the amount of memory of the specified type that is available to the applet. Note that implementation-dependent memory overhead structures may also use the same memory pool.

Notes:

• The number of bytes returned is only an upper bound on the amount of memory available due to overhead requirements.
• Allocation of CLEAR_ON_RESET transient objects may affect the amount of CLEAR_ON_DESELECT transient memory available.
• Allocation of CLEAR_ON_DESELECT transient objects may affect the amount of CLEAR_ON_RESET transient memory available.
• If the number of available bytes is greater than 32767, then this method returns 32767.
• The returned count is not an indicator of the size of object which may be created since memory fragmentation is possible.

Parameters:

memoryType - the type of memory being queried. One of the MEMORY_TYPE_.. constants defined above. See MEMORY_TYPE_PERSISTENT

Returns:

the upper bound on available bytes of memory for the specified type

Throws:

SystemException - with the following reason codes:

• SystemException.ILLEGAL_VALUE if memoryType is not a valid memory type.

makeTransientObjectArray

public static Object[] makeTransientObjectArray(short length,
                                                byte event)
                                         throws NegativeArraySizeException,
                                                SystemException

Creates a transient array of Object with the specified array length.

Parameters:

length - the length of the Object array

event - the CLEAR_ON... event which causes the array elements to be cleared

Returns:

the new transient Object array

Throws:

NegativeArraySizeException - if the length parameter is negative

SystemException - with the following reason codes:

• SystemException.ILLEGAL_VALUE if event is not a valid event code.
• SystemException.NO_TRANSIENT_SPACE if sufficient transient space is not available.
• SystemException.ILLEGAL_TRANSIENT if the current applet context is not the currently selected applet context and CLEAR_ON_DESELECT is specified.

abortTransaction

public static void abortTransaction()
                             throws TransactionException

Aborts the atomic transaction. The contents of the commit buffer is discarded.

Note:

• This method may do nothing if the Applet.register() method has not yet been invoked. In case of tear or failure prior to successful registration, the Java Card runtime environment will roll back all atomically updated persistent state.
• Do not call this method from within a transaction which creates new objects because the Java Card runtime environment may not recover the heap space used by the new object instances.
• Do not call this method from within a transaction which creates new objects because the Java Card runtime environment may, to ensure the security of the card and to avoid heap space loss, lock up the card session to force tear/reset processing.
• The Java Card runtime environment ensures that any variable of reference type which references an object instantiated from within this aborted transaction is equivalent to a null reference.

Throws:

TransactionException - with the following reason codes:

• TransactionException.NOT_IN_PROGRESS if a transaction is not in progress.

See Also:

beginTransaction()

getAppletShareableInterfaceObject

public static Shareable getAppletShareableInterfaceObject(AID serverAID,
                                                          byte parameter)

Called by a client applet to get a server applet's shareable interface object.

This method returns null if:

• the Applet.register() has not yet been invoked
• the server does not exist
• the server returns null

Parameters:

serverAID - the AID of the server applet

parameter - optional parameter data

Returns:

the shareable interface object or null

See Also:

Applet.getShareableInterfaceObject(javacard.framework.AID, byte)

makeTransientShortArray

public static short[] makeTransientShortArray(short length,
                                              byte event)
                                       throws NegativeArraySizeException,
                                              SystemException

Creates a transient short array with the specified array length.

Parameters:

length - the length of the short array

event - the CLEAR_ON... event which causes the array elements to be cleared

Returns:

the new transient short array

Throws:

NegativeArraySizeException - if the length parameter is negative

SystemException - with the following reason codes:

• SystemException.ILLEGAL_VALUE if event is not a valid event code.
• SystemException.NO_TRANSIENT_SPACE if sufficient transient space is not available.
• SystemException.ILLEGAL_TRANSIENT if the current applet context is not the currently selected applet context and CLEAR_ON_DESELECT is specified.

lookupAID

public static AID lookupAID(byte[] buffer,
                            short offset,
                            byte length)

Returns the Java Card runtime environment-owned instance of the AID object, if any, encapsulating the specified AID bytes in the buffer parameter if there exists a successfully installed applet on the card whose instance AID exactly matches that of the specified AID bytes.

Java Card runtime environment-owned instances of AID are permanent Java Card runtime environment Entry Point Objects and can be accessed from any applet context. References to these permanent objects can be stored and re-used.

See Runtime Environment Specification for the Java Card Platform, section 6.2.1 for details.

Parameters:

buffer - byte array containing the AID bytes

offset - offset within buffer where AID bytes begin

length - length of AID bytes in buffer

Returns:

the AID object, if any; null otherwise. A VM exception is thrown if buffer is null, or if offset or length are out of range.