我想获取Mifare Ultralight NFC标签的UID。在Java中，我有以下代码：
TerminalFactory factory = TerminalFactory.getDefault();
List<CardTerminal> terminals = factory.terminals().list();
System.out.println("Terminals: " + terminals);
CardTerminal terminal = terminals.get(0);
Card card = terminal.connect("*");
System.out.println("card: " + card);
CardChannel channel = card.getBasicChannel();
ResponseAPDU answer = channel.transmit(new CommandAPDU(0xFF, 0xCA, 0x00, 0x00, 0x00));
byte[] uid = answer.getBytes();
问题是我收到两个字节而不是 UID。怎么了？APDU 是否正确？
您实际使用的命令不是您所期望的。
使用此读取器获取 UID/序列号/枚举标识符的正确命令 APDU 是：
+------+------+------+------+------+
| CLA | INS | P1 | P2 | Le |
+------+------+------+------+------+
| 0xFF | 0xCA | 0x00 | 0x00 | 0x00 |
+------+------+------+------+------+
但是，您使用的构造函数定义为：
public CommandAPDU(int cla, int ins, int p1, int p2, int ne);
所以用
new CommandAPDU(0xFF, 0xCA, 0x00, 0x00, 0x00)
您正在创建一个具有以下参数的 C-APDU CLA = 0xFF 、 INS = 0xCA 、 P1 = 0x00 、 P2 = 0x00 。到目前为止，这与上述APDU相同。但是最后一个参数是 Ne = 0x00 . Ne = 0 表示预期响应字节数为零（而 Le = 0 表示预期响应字节数（最多）256）。
这将有效地创建以下案例 1 APDU：
+------+------+------+------+
| CLA | INS | P1 | P2 |
+------+------+------+------+
| 0xFF | 0xCA | 0x00 | 0x00 |
+------+------+------+------+
因此，您最多会得到 2 字节的状态字作为响应（表示 0x90 0x00 成功或指示状态代码的错误，如 0x6X 0xXX ）。
因此，您可以使用字节数组来形成您的 APDU：
new CommandAPDU(new byte[] { (byte)0xFF, (byte)0xCA, (byte)0x00, (byte)0x00, (byte)0x00 } )
或者，您可以为Ne指定适当的值：
new CommandAPDU(0xFF, 0xCA, 0x00, 0x00, 256)
import java.nio.ByteBuffer;
import java.util.List;
import javax.smartcardio.Card;
import javax.smartcardio.CardChannel;
import javax.smartcardio.CardException;
import javax.smartcardio.CardTerminal;
import javax.smartcardio.TerminalFactory;
public class Read {
public Read() {
try {
CardTerminal terminal = null;
// show the list of available terminals
TerminalFactory factory = TerminalFactory.getDefault();
List<CardTerminal> terminals = factory.terminals().list();
String readerName = "";
for (int i = 0; i < terminals.size(); i++) {
readerName = terminals.get(i).toString()
.substring(terminals.get(i).toString().length() - 2);
//terminal = terminals.get(i);
if (readerName.equalsIgnoreCase(" 0")) {
terminal = terminals.get(i);
}
}
// Establish a connection with the card
System.out.println("Waiting for a card..");
if(terminal==null)
return;
terminal.waitForCardPresent(0);
Card card = terminal.connect("T=0");
CardChannel channel = card.getBasicChannel();
// Start with something simple, read UID, kinda like Hello World!
byte[] baReadUID = new byte[5];
baReadUID = new byte[] { (byte) 0xFF, (byte) 0xCA, (byte) 0x00,
(byte) 0x00, (byte) 0x00 };
System.out.println("UID: " + send(baReadUID, channel));
// If successfull, the output will end with 9000
// OK, now, the real work
} catch (Exception ex) {
ex.printStackTrace();
}
}
public String send(byte[] cmd, CardChannel channel) {
String res = "";
byte[] baResp = new byte[258];
ByteBuffer bufCmd = ByteBuffer.wrap(cmd);
ByteBuffer bufResp = ByteBuffer.wrap(baResp);
// output = The length of the received response APDU
int output = 0;
try {
output = channel.transmit(bufCmd, bufResp);
}` catch (CardException ex) {
ex.printStackTrace();
}`
for (int i = 0; i < output; i++) {
res += String.format("%02X", baResp[i]);
// The result is formatted as a hexadecimal integer
}
return res;
}
public static void main(String[] args) {
new Read();
}
}
阅读此代码后 出于读写目的，请使用以下命令。
并从页面读取：04到页面：07命令是：
read_four_to_seven = new byte[]{(byte) 0xFF, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x05, (byte) 0x0D4, (byte) 0x40, (byte) 0x01,
(byte) 0x30, (byte) 0x04, (byte) 0x07 };
System.out.println("Read : " + send(read_four_to_seven, channel));
写到第04页：
Write_Page_Four = new byte[] { (byte) 0xFF, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x15, (byte) 0xD4, (byte) 0x40,
(byte) 0x01, (byte) 0xA0, (byte) 0x04, (byte) 0x4D,
(byte) 0x65, (byte) 0x73, (byte) 0x75, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x00,
(byte) 0x00, (byte) 0x00, (byte) 0x00 };
System.out.println("Read : " + send(Write_Page_Four, channel));