XAXid.java

package cn.dreampie.common.plugin.db.tx;

import java.net.Inet4Address;
import java.util.Random;

/**
 * Created by wangrenhui on 2014/5/9.
 */
public class XAXid implements javax.transaction.xa.Xid {

    int formatId;
    byte[] globalTransactionId;
    byte[] branchQualifier;

    public XAXid(int formatId, byte[] globalTransactionId, byte[] branchQualifier) {
        this.formatId = formatId;
        this.globalTransactionId = globalTransactionId;
        this.branchQualifier = branchQualifier;
    }

    @Override
    public int getFormatId() {
        return formatId;
    }

    @Override
    public byte[] getGlobalTransactionId() {
        return globalTransactionId;
    }

    @Override
    public byte[] getBranchQualifier() {
        return branchQualifier;
    }

    // Returns a globally unique transaction id.
    static byte[] localIP = null;
    static int txnUniqueID = 0;

    public static XAXid uniqueXid(int tid) {

        Random rnd = new Random(System.currentTimeMillis());
        txnUniqueID++;
        int txnUID = txnUniqueID;
        int tidID = tid;
        int randID = rnd.nextInt();
        byte[] gtrid = new byte[64];
        byte[] bqual = new byte[64];
        if (null == localIP) {
            try {
                localIP = Inet4Address.getLocalHost().getAddress();
            } catch (Exception ex) {
                localIP = new byte[]{0x01, 0x02, 0x03, 0x04};
            }
        }
        System.arraycopy(localIP, 0, gtrid, 0, 4);
        System.arraycopy(localIP, 0, bqual, 0, 4);

        // Bytes 4 -> 7 - unique transaction id.
        // Bytes 8 ->11 - thread id.
        // Bytes 12->15 - random number generated by using seed from current time in milliseconds.
        for (int i = 0; i <= 3; i++) {
            gtrid[i + 4] = (byte) (txnUID % 0x100);
            bqual[i + 4] = (byte) (txnUID % 0x100);
            txnUID >>= 8;
            gtrid[i + 8] = (byte) (tidID % 0x100);
            bqual[i + 8] = (byte) (tidID % 0x100);
            tidID >>= 8;
            gtrid[i + 12] = (byte) (randID % 0x100);
            bqual[i + 12] = (byte) (randID % 0x100);
            randID >>= 8;
        }
        return new XAXid(0x1234, gtrid, bqual);
    }
}