移动支付之智能IC卡与Android手机进行NFC通信
智能IC卡的Applet不能自己启动，必须由外部终端（比如POS机，地铁刷卡终端等）向卡片发送Select命令，由此选中卡片的Applet，Applet才干执行。Appplet側重于数据的处理。没有花销的I/O功能。
Applet的程序有生命周期和指定入口，当中最基本的几个方法例如以下：
- public static void install(byte[] bArray, short bOffset, byte bLength)
构建了Applet子类的实例，JCRE将会最先调用这个；全部的初始化和分配内存的操作应该在这个里面实现；能够获取卡外实体传进来的一些应用初始化參数。
- public void process(APDU apdu)
相似于正常java class的main，在安装后，APDU的执行将在这里实现。- protected final void register()
applet用来在JCRE中注冊该applet实例- register(byte[] bArray, short bOffset, byte bLength)
register( )功能一样，添加了能够分配其特定的AID的功能。- public boolean select()
JCRE一旦接收到SELECT[by name]命令时，将寻找命令中指示的AID相应的Applet。使之处于活跃状态，接收并处理接下来的APDU命令。在选择新的Applet前。JCRE先调用当前Applet的 deselect 方法；Applet能够拒绝被选择，此时 select 方法返回false。SELECT[by name]命令本身也将传递给applet处理，此时通过 selectingApplet 用以推断当前状态。 本文的DEMO执行效果例如以下。包括一个JavaCard的Applet实现和一个Android端的NFC读敲代码，实现智能IC卡与Android手机的简单通信。
接下来贴段简单的Applet 源代码。下载地址：http://download.csdn.net/detail/hellogv/8090041。
大概的思路是：Applet定义了2个开头标识皆为CMD_CLA的自己定义命令CMD_INS_1和CMD_INS_2，当Android手机通过NFC分别发送CMD_INS_1和CMD_INS_2，Applet分别返回strHello和strWorld。
核心源代码例如以下：
public class mytest extends Applet {
private static final byte[] strHello= { (byte) 'H', (byte) 'e',
(byte) 'l', (byte) 'l', (byte) 'o'};
private static final byte[] strWorld = {(byte) 'W',
(byte) 'o', (byte) 'r', (byte) 'l', (byte) 'd', };
private static final byte CMD_CLA = (byte) 0x80;
private static final byte CMD_INS_1 = (byte) 0x10;
private static final byte CMD_INS_2 = (byte) 0x20;
public static void install(byte[] bArray, short bOffset, byte bLength) {
// GP-compliant JavaCard applet registration
new mytest().register(bArray, (short) (bOffset + 1), bArray[bOffset]);
}
/*
* 当Java卡Applet被选中时，由JCRE调用。Java卡Applet能够定义select()完毕初始化。
* 否则。JCRE调用父类的select()。
* @see javacard.framework.Applet#select()
*/
public boolean select() {
short debug=100;
debug++;//用于断点调试，当被select时触发。
return super.select();
}
/*
* 当Java卡Applet被放弃时，由JCRE调用。
Java卡Applet能够定义deselect()完毕清除。
* 否则，JCRE调用父类的deselect()。
* @see javacard.framework.Applet#deselect()
*/
public void deselect() {
short debug=100;
debug++;//用于断点调试
super.deselect();
}
/*
* 每次收到APDU命令。都会执行
* @see javacard.framework.Applet#process(javacard.framework.APDU)
*/
public void process(APDU apdu) {
if (selectingApplet()) {
return;
}
//获取外部终端发过来的数据
byte[] buffer = apdu.getBuffer();
//获取第一位数据
byte CLA = (byte) (buffer[ISO7816.OFFSET_CLA] & 0xFF);
//获取第二位数据
byte INS = (byte) (buffer[ISO7816.OFFSET_INS] & 0xFF);
if (CLA != CMD_CLA) {//格式不正确
ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);
}
switch (INS) {
case CMD_INS_1:
sendBytes(apdu,strHello);
break;
case CMD_INS_2:
sendBytes(apdu,strWorld);
break;
default:
ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
}
}
private void sendBytes(APDU apdu,byte[] arrays) {
byte[] buffer = apdu.getBuffer();
short length = (short) arrays.length;
Util.arrayCopyNonAtomic(arrays, (short) 0, buffer, (short) 0,
(short) length);
apdu.setOutgoingAndSend((short) 0, length);
}
}
接下来贴出Android端的核心代码。下载地址：http://download.csdn.net/detail/hellogv/8090053。
大概的思路是：Android端的NFC读敲代码定义1个Applet的ID（AID）。SELECT命令的报文头（SELECT_APDU_HEADER），2个自己定义命令CMD_INS_1和CMD_INS_2。首先使用AID和SELECT_APDU_HEADER生成完整的SELECT命令。transceive（发送）到卡片，用于启动卡片里的AID相应的Applet。启动卡片里的Applet后，NFC读敲代码发送SAMPLE_COMMAND里面的2条自己定义命令，Applet分别返回"Hello""World"。
核心源代码例如以下：
public final class CardReader {
private static final String TAG = "LoyaltyCardReader";
// AID for our loyalty card service.
private static final String SAMPLE_CARD_AID = "1122001122";
// ISO-DEP command HEADER for selecting an AID.
// Format: [Class | Instruction | Parameter 1 | Parameter 2]
private static final String SELECT_APDU_HEADER = "00A40400";
// "OK" status word sent in response to SELECT AID command (0x9000)
private static final byte[] SELECT_OK_SW = {(byte) 0x90, (byte) 0x00};
//自己定义的命令
private static final String[] SAMPLE_COMMAND={"8010000000",//卡片收到后返回"Hello"
"8020000000"};//卡片收到后返回"World"
public static String[][] TECHLISTS;
public static IntentFilter[] FILTERS;
static {
try {
//the tech lists used to perform matching for dispatching of the ACTION_TECH_DISCOVERED intent
TECHLISTS = new String[][] { { IsoDep.class.getName() }};
FILTERS = new IntentFilter[] { new IntentFilter(
NfcAdapter.ACTION_TECH_DISCOVERED, "*/*") };
} catch (Exception e) {
}
}
static public String tagDiscovered(Tag tag) {
Log.e(TAG, "New tag discovered");
String strResult="";
IsoDep isoDep = IsoDep.get(tag);
if (isoDep != null) {
try {
// Connect to the remote NFC device
isoDep.connect();
//发送select 命令,卡片会返回SELECT_OK_SW（90 00）
byte[] cmdSelect = BuildSelectApdu(SAMPLE_CARD_AID);
Log.e(TAG, "Sending: " + ByteArrayToHexString(cmdSelect));
byte[] result = isoDep.transceive(cmdSelect);
Log.e(TAG, "Receive: " + ByteArrayToHexString(result));
byte[][] response = getResponse(result);
byte[] statusWord =response[0];
if (Arrays.equals(SELECT_OK_SW, statusWord) == false)
return "";
//循环发送自己定义命令
for(int i=0;i<SAMPLE_COMMAND.length;i++){
String command = SAMPLE_COMMAND[i];
result = HexStringToByteArray(command);
Log.e(TAG, "Sending: " + command);
result = isoDep.transceive(result);
Log.e(TAG, "Receive: " + ByteArrayToHexString(result));
response = getResponse(result);
byte[] body =response[1];
strResult=strResult+new String(body)+":"+ByteArrayToHexString(body)+"\r\n";
}
return strResult;
} catch (IOException e) {
Log.e(TAG, "Error communicating with card: " + e.toString());
}
}
return null;
}
/***
* 分解卡片返回的数据
* @param b
* @return [0]表示返回的状态值，[1]表示返回的正文
*/
private static byte[][] getResponse(byte[] b){
byte[][] result = new byte[2][];
int length = b.length;
byte[] status = { b[length - 2],b[length - 1] };
byte[] body = Arrays.copyOf(b, length - 2);
result[0]=status;
result[1]=body;
return result;
}
public static String load(Parcelable parcelable) {
// 从Parcelable筛选出各类NFC标准数据
final Tag tag = (Tag) parcelable;
return tagDiscovered(tag);
}
/**
* Build APDU for SELECT AID command. This command indicates which service a reader is
* interested in communicating with. See ISO 7816-4.
*
* @param aid Application ID (AID) to select
* @return APDU for SELECT AID command
*/
public static byte[] BuildSelectApdu(String aid) {
// Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA]
return HexStringToByteArray(SELECT_APDU_HEADER + String.format("%02X", aid.length() / 2) + aid);
}
/**
* Utility class to convert a byte array to a hexadecimal string.
*
* @param bytes Bytes to convert
* @return String, containing hexadecimal representation.
*/
public static String ByteArrayToHexString(byte[] bytes) {
final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
char[] hexChars = new char[bytes.length * 2];
int v;
for ( int j = 0; j < bytes.length; j++ ) {
v = bytes[j] & 0xFF;
hexChars[j * 2] = hexArray[v >>> 4];
hexChars[j * 2 + 1] = hexArray[v & 0x0F];
}
return new String(hexChars);
}
/**
* Utility class to convert a hexadecimal string to a byte string.
*
* <p>Behavior with input strings containing non-hexadecimal characters is undefined.
*
* @param s String containing hexadecimal characters to convert
* @return Byte array generated from input
*/
public static byte[] HexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}
}