tlv 格式解析

/**
 * 将字符串转换为TLV对象
 * 
 */
public abstract class TlvUtils {

	/**
	 * 将16进制字符串转换为TLV对象列表
	 * @param hexString
	 * @return
	 */
	public static List builderTlvList(String hexString) {
		List tlvs = new ArrayList();

		int position = 0;
		while (position != StringUtils.length(hexString)) {
			String _hexTag = getTag(hexString, position);
			position += _hexTag.length();

			LPositon l_position = getLengthAndPosition(hexString, position);
			int _vl = l_position.get_vL();

			position = l_position.get_position();

			String _value = StringUtils.substring(hexString, position, position + _vl * 2);

			position = position + _value.length();

			tlvs.add(new Tlv(_hexTag, _vl, _value));
		}
		return tlvs;
	}
	
	/**
	 * 将16进制字符串转换为TLV对象MAP
	 * @param hexString
	 * @return
	 */
	public static Map builderTlvMap(String hexString) {

		Map tlvs = new HashMap();

		int position = 0;
		while (position != hexString.length()) {
			String _hexTag = getTag(hexString, position);
			
			position += _hexTag.length();
			
			LPositon l_position = getLengthAndPosition(hexString, position);
			
			int _vl = l_position.get_vL();
			position = l_position.get_position();
			String _value = hexString.substring(position, position + _vl * 2);
			position = position + _value.length();
			
			tlvs.put(_hexTag, new Tlv(_hexTag, _vl, _value));
		}
		return tlvs;
	}
	
	/**
	 * 返回最后的Value的长度
	 * 
	 * @param hexString
	 * @param position
	 * @return 
	 */
	private static LPositon getLengthAndPosition(String hexString, int position) {
		String firstByteString = hexString.substring(position, position + 2);
		int i = Integer.parseInt(firstByteString, 16);
		String hexLength = "";

		if (((i >>> 7) & 1) == 0) {
			hexLength = hexString.substring(position, position + 2);
			position = position + 2;
		} else {
			// 当最左侧的bit位为1的时候，取得后7bit的值，
			int _L_Len = i & 127;
			position = position + 2;
			hexLength = hexString.substring(position, position + _L_Len * 2);
			// position表示第一个字节，后面的表示有多少个字节来表示后面的Value值
			position = position + _L_Len * 2;
		}
		return new LPositon(Integer.parseInt(hexLength, 16), position);

	}

	/**
	 * 取得子域Tag标签
	 * 
	 * @param hexString
	 * @param position
	 * @return
	 */
	private static String getTag(String hexString, int position) {
		String firstByte = StringUtils.substring(hexString, position, position + 2);
		int i = Integer.parseInt(firstByte, 16);
		if ((i & 0x1f) == 0x1f) {
			return hexString.substring(position, position + 4);

		} else {
			return hexString.substring(position, position + 2);
		}
	}
}
 
  
 
  
 
  
 
  
 
  
/**
 * value的长度
 */
public class LPositon {

	private int _vL;
	private int _position;

	public LPositon(int _vL, int position) {
		this._vL = _vL;
		this._position = position;
	}

	public int get_vL() {
		return _vL;
	}

	public void set_vL(int _vL) {
		this._vL = _vL;
	}

	public int get_position() {
		return _position;
	}

	public void set_position(int _position) {
		this._position = _position;
	}
}
 
  
 TLV：TLV格式数据是指由Tag，Length，Value组成的数据。具体说明如下： 
  
 
  

 
  
 
  
 Type和Length的长度固定，一般那是2、4个字节（这里统一采用4个字节）；
 
  
 Value的长度有Length指定
 
  
 编码格式：
 
  
 1.       将类型type转换为网络字节顺序，指针偏移+4
 
  
 2.       将长度length转换为网络字节顺序，指针偏移+4
 
  
 3.       若值value数据类型为int、char、short，则将其转换为网络字节顺序，指针偏移+4；若值为字符串类型，写进后，指针偏移+length
 
  
 ……继续处理后面的tlv；
 
  
 解码格式：（和编码格式相反）
 
  
 
 
  
 
 
  
 类型(Type)字段是关于标签和编码格式的信息；
 
  
 长度 (Length)字段定义数值的长度；
 
  
 内容(Value)字段表示实际的数值。
 
  
 
  
 public class Tlv {


/** 子域Tag标签 */
private String tag;


/** 子域取值的长度 */
private int length;


/** 子域取值 */
private String value;


public Tlv(String tag, int length, String value) {
this.length = length;
this.tag = tag;
this.value = value;
}


public String getTag() {
return tag;
}


public void setTag(String tag) {
this.tag = tag;
}


public int getLength() {
return length;
}


public void setLength(int length) {
this.length = length;
}


public String getValue() {
return value;
}


public void setValue(String value) {
this.value = value;
}


@Override
public String toString() {
return "tag=[" + this.tag + "]," + "length=[" + this.length + "]," + "value=[" + this.value + "]";
}
 }
 
  
 
 
  
 http://my.oschina.net/maxid/blog/206546