jcsystem.html

JAVA CARD 开发包规格说明,版本为2.2.2

</DD>
</DL>
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<A NAME="getMaxCommitCapacity()"><!-- --></A><H3>
getMaxCommitCapacity</H3>
<PRE>
public static short <B>getMaxCommitCapacity</B>()</PRE>
<DL>
<DD>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.
 <p> Note:<ul>
 <li><em>If the total number of bytes in the commit buffer is greater than
 32767, then this method returns 32767.</em>
 </ul>
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the total number of bytes in the commit buffer<DT><B>See Also:</B><DD><A HREF="../../javacard/framework/JCSystem.html#getUnusedCommitCapacity()"><CODE>getUnusedCommitCapacity()</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="getPreviousContextAID()"><!-- --></A><H3>
getPreviousContextAID</H3>
<PRE>
public static <A HREF="../../javacard/framework/AID.html" title="class in javacard.framework">AID</A> <B>getPreviousContextAID</B>()</PRE>
<DL>
<DD>Obtains the Java Card runtime environment-owned instance of the <code>AID</code> 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.
 <p>Java Card runtime environment-owned instances of <code>AID</code> 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.
 <p>See <em>Runtime Environment Specification for the Java Card Platform</em>, section 6.2.1 for details.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the <code>AID</code> object of the previous context, or <code>null</code> if Java Card runtime environment</DL>
</DD>
</DL>
<HR>

<A NAME="getAvailableMemory(byte)"><!-- --></A><H3>
getAvailableMemory</H3>
<PRE>
public static short <B>getAvailableMemory</B>(byte&nbsp;memoryType)
                                throws <A HREF="../../javacard/framework/SystemException.html" title="class in javacard.framework">SystemException</A></PRE>
<DL>
<DD>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.
 <p>Notes:<ul>
 <li><em>The number of bytes returned is only an upper bound on the amount
 of memory available due to overhead requirements.</em>
 <li><em>Allocation of CLEAR_ON_RESET transient objects may affect the
 amount of CLEAR_ON_DESELECT transient memory available.</em>
 <li><em>Allocation of CLEAR_ON_DESELECT transient objects may affect the
 amount of CLEAR_ON_RESET transient memory available.</em>
 <li><em>If the number of available bytes is greater than 32767, then
 this method returns 32767.</em>
 <li><em>The returned count is not an indicator of the size of object which
 may be created since memory fragmentation is possible.</em>
 </ul>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>memoryType</CODE> - the type of memory being queried. One of the <CODE>MEMORY_TYPE_*</CODE>
 constants defined above. See <A HREF="../../javacard/framework/JCSystem.html#MEMORY_TYPE_PERSISTENT"><CODE>MEMORY_TYPE_PERSISTENT</CODE></A>.
<DT><B>Returns:</B><DD>the upper bound on available bytes of memory for the specified type
<DT><B>Throws:</B>
<DD><CODE><A HREF="../../javacard/framework/SystemException.html" title="class in javacard.framework">SystemException</A></CODE> - with the following reason codes:<ul>
 <li><code>SystemException.ILLEGAL_VALUE</code> if <code>memoryType</code> is not a
 valid memory type.
 </ul></DL>
</DD>
</DL>
<HR>

<A NAME="getAppletShareableInterfaceObject(javacard.framework.AID, byte)"><!-- --></A><H3>
getAppletShareableInterfaceObject</H3>
<PRE>
public static <A HREF="../../javacard/framework/Shareable.html" title="interface in javacard.framework">Shareable</A> <B>getAppletShareableInterfaceObject</B>(<A HREF="../../javacard/framework/AID.html" title="class in javacard.framework">AID</A>&nbsp;serverAID,
                                                          byte&nbsp;parameter)</PRE>
<DL>
<DD>Called by a client applet to get a server applet's
 shareable interface object. <p>This method returns <code>null</code>
 if:
 <ul>
   <li>the <code>Applet.register()</code> has not yet been invoked</li>
   <li>the server applet does not exist</li>
   <li>the server applet returns <code>null</code></li>
   <li>the server applet throws an uncaught exception</li>
 </ul>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>serverAID</CODE> - the AID of the server applet<DD><CODE>parameter</CODE> - optional parameter data
<DT><B>Returns:</B><DD>the shareable interface object or <code>null</code>
<DT><B>Throws:</B>
<DD><CODE><A HREF="../../java/lang/SecurityException.html" title="class in java.lang">SecurityException</A></CODE> - if the server applet is not multiselectable and
 is currently active on another logical channel
 </ul><DT><B>See Also:</B><DD><A HREF="../../javacard/framework/Applet.html#getShareableInterfaceObject(javacard.framework.AID, byte)"><CODE>Applet.getShareableInterfaceObject(AID, byte)</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="isObjectDeletionSupported()"><!-- --></A><H3>
isObjectDeletionSupported</H3>
<PRE>
public static boolean <B>isObjectDeletionSupported</B>()</PRE>
<DL>
<DD>This method is used to determine if the implementation for the Java Card platform supports
 the object deletion mechanism.
<P>
<DD><DL>

<DT><B>Returns:</B><DD><CODE>true</CODE> if the object deletion mechanism is supported, <CODE>false</CODE> otherwise</DL>
</DD>
</DL>
<HR>

<A NAME="requestObjectDeletion()"><!-- --></A><H3>
requestObjectDeletion</H3>
<PRE>
public static void <B>requestObjectDeletion</B>()
                                  throws <A HREF="../../javacard/framework/SystemException.html" title="class in javacard.framework">SystemException</A></PRE>
<DL>
<DD>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 <CODE>Applet.process()</CODE> method. The object deletion
 mechanism must ensure that : <ul>
 <li>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 <CODE>Applet.process()</CODE> method.
 <li>Any unreferenced <CODE>CLEAR_ON_DESELECT</CODE> or <CODE>CLEAR_ON_RESET</CODE>
 transient object owned by the current applet context is deleted
 and the associated space is recovered for reuse before the next card reset session.
 </ul>
<P>
<DD><DL>

<DT><B>Throws:</B>
<DD><CODE><A HREF="../../javacard/framework/SystemException.html" title="class in javacard.framework">SystemException</A></CODE> - with the following reason codes:<ul>
 <li><code>SystemException.ILLEGAL_USE</code> if the object deletion mechanism is
 not implemented.
 </ul></DL>
</DD>
</DL>
<HR>

<A NAME="getAssignedChannel()"><!-- --></A><H3>
getAssignedChannel</H3>
<PRE>
public static byte <B>getAssignedChannel</B>()</PRE>
<DL>
<DD>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 <CODE>Applet.select()</CODE>, <CODE>Applet.deselect(</CODE>),
 <CODE>MultiSelectable.select(boolean)</CODE> and <CODE>MultiSelectable.deselect(boolean)</CODE> methods
 during MANAGE CHANNEL APDU command processing, the logical channel number
 returned may be different.
<P>
<DD><DL>

<DT><B>Returns:</B><DD>the logical channel number in the range 0-19 assigned to the
 currently selected applet instance</DL>
</DD>
</DL>
<HR>

<A NAME="isAppletActive(javacard.framework.AID)"><!-- --></A><H3>
isAppletActive</H3>
<PRE>
public static boolean <B>isAppletActive</B>(<A HREF="../../javacard/framework/AID.html" title="class in javacard.framework">AID</A>&nbsp;theApplet)</PRE>
<DL>
<DD>This method is used to determine if the specified applet is
 active on the card.
 <p>Note:<ul>
 <li><em>This method returns <code>false</code> if the specified applet is
 not active, even if its context is active.</em>
 </ul>
<P>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>theApplet</CODE> - the AID of the applet object being queried
<DT><B>Returns:</B><DD><code>true</code> if and only if the applet specified by the
 AID parameter is currently active on this or another logical channel<DT><B>See Also:</B><DD><A HREF="../../javacard/framework/JCSystem.html#lookupAID(byte[], short, byte)"><CODE>lookupAID( byte[] buffer, short offset, byte length )</CODE></A></DL>
</DD>
</DL>
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