=== modified file 'src/com/mysql/jdbc/jdbc2/optional/MysqlXAConnection.java'
--- src/com/mysql/jdbc/jdbc2/optional/MysqlXAConnection.java	2013-09-18 10:45:06 +0000
+++ src/com/mysql/jdbc/jdbc2/optional/MysqlXAConnection.java	2014-02-07 11:53:10 +0000
@@ -379,9 +379,9 @@
 	 *             XAER_PROTO.
 	 */
 	public int prepare(Xid xid) throws XAException {
-		StringBuffer commandBuf = new StringBuffer();
+		StringBuilder commandBuf = new StringBuilder(210);
 		commandBuf.append("XA PREPARE ");
-		commandBuf.append(xidToString(xid));
+        appendXid(xid, commandBuf);
 
 		dispatchCommand(commandBuf.toString());
 
@@ -421,9 +421,9 @@
 	 * has released all held resources.
 	 */
 	public void rollback(Xid xid) throws XAException {
-		StringBuffer commandBuf = new StringBuffer();
+		StringBuilder commandBuf = new StringBuilder(211);
 		commandBuf.append("XA ROLLBACK ");
-		commandBuf.append(xidToString(xid));
+        appendXid(xid, commandBuf);
 
 		try {
 			dispatchCommand(commandBuf.toString());
@@ -460,9 +460,9 @@
 	 *             or XA_RB*.
 	 */
 	public void end(Xid xid, int flags) throws XAException {
-		StringBuffer commandBuf = new StringBuffer();
+		StringBuilder commandBuf = new StringBuilder(206);
 		commandBuf.append("XA END ");
-		commandBuf.append(xidToString(xid));
+        appendXid(xid, commandBuf);
 
 		switch (flags) {
 		case TMSUCCESS:
@@ -503,9 +503,9 @@
 	 *             XAER_INVAL, or XAER_PROTO.
 	 */
 	public void start(Xid xid, int flags) throws XAException {
-		StringBuffer commandBuf = new StringBuffer();
+		StringBuilder commandBuf = new StringBuilder(208);
 		commandBuf.append("XA START ");
-		commandBuf.append(xidToString(xid));
+        appendXid(xid, commandBuf);
 
 		switch (flags) {
 		case TMJOIN:
@@ -548,16 +548,16 @@
 	 */
 
 	public void commit(Xid xid, boolean onePhase) throws XAException {
-		StringBuffer commandBuf = new StringBuffer();
+		StringBuilder commandBuf = new StringBuilder(219);
 		commandBuf.append("XA COMMIT ");
-		commandBuf.append(xidToString(xid));
+        appendXid(xid, commandBuf);
 
 		if (onePhase) {
 			commandBuf.append(" ONE PHASE");
 		}
 
 		try {
-			dispatchCommand(commandBuf.toString());
+            dispatchCommand(commandBuf.toString());
 		} finally {
 			this.underlyingConnection.setInGlobalTx(false);
 		}
@@ -605,7 +605,7 @@
 		return new MysqlXAException(sqlEx.getMessage(), null);
 	}
 
-	private static String xidToString(Xid xid) {
+	private static void appendXid(Xid xid, StringBuilder toAppendTo) {
 		byte[] gtrid = xid.getGlobalTransactionId();
 
 		byte[] btrid = xid.getBranchQualifier();
@@ -620,48 +620,60 @@
 			lengthAsString += (2 * btrid.length);
 		}
 
-		String formatIdInHex = Integer.toHexString(xid.getFormatId());
-
-		lengthAsString += formatIdInHex.length();
+		lengthAsString += 8; // for formatId
 		lengthAsString += 3; // for the '.' after formatId
 
-		StringBuffer asString = new StringBuffer(lengthAsString);
+        toAppendTo.ensureCapacity(lengthAsString + toAppendTo.length());
 
-		asString.append("0x");
+		toAppendTo.append("0x");
 
 		if (gtrid != null) {
-			for (int i = 0; i < gtrid.length; i++) {
-				String asHex = Integer.toHexString(gtrid[i] & 0xff);
-
-				if (asHex.length() == 1) {
-					asString.append("0");
-				}
-
-				asString.append(asHex);
-			}
+            encode(toAppendTo, gtrid);
 		}
 
-		asString.append(",");
+		toAppendTo.append(',');
 
 		if (btrid != null) {
-			asString.append("0x");
-
-			for (int i = 0; i < btrid.length; i++) {
-				String asHex = Integer.toHexString(btrid[i] & 0xff);
-
-				if (asHex.length() == 1) {
-					asString.append("0");
-				}
-
-				asString.append(asHex);
-			}
+			toAppendTo.append("0x");
+            encode(toAppendTo, btrid);
 		}
 
-		asString.append(",0x");
-		asString.append(formatIdInHex);
-
-		return asString.toString();
-	}
+		toAppendTo.append(",0x");
+
+        int formatId = xid.getFormatId();
+
+        byte int3 = (byte) (formatId >> 24);
+        byte int2 = (byte) (formatId >> 16);
+        byte int1 = (byte) (formatId >>  8);
+        byte int0 = (byte) (formatId      );
+        if (int3 != 0) {
+            toAppendTo.append(DIGITS[(0xF0 & int3) >>> 4])
+                      .append(DIGITS[0x0F & int3]);
+        }
+        if (int2 != 0) {
+            toAppendTo.append(DIGITS[(0xF0 & int2) >>> 4])
+                      .append(DIGITS[0x0F & int2]);
+        }
+        if (int1 != 0) {
+            toAppendTo.append(DIGITS[(0xF0 & int1) >>> 4])
+                      .append(DIGITS[0x0F & int1]);
+        }
+        toAppendTo.append(DIGITS[(0xF0 & int0) >>> 4])
+                  .append(DIGITS[0x0F & int0]);
+    }
+
+    private static final char[] DIGITS = {
+        '0', '1', '2', '3', '4', '5', '6', '7',
+        '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+    private static void encode(StringBuilder builder, byte[] bytes) {
+        byte b;
+        for (int i = 0, l = bytes.length; i < l; i++) {
+            b = bytes[i];
+            builder.append(DIGITS[(0xF0 & b) >>> 4])
+                   .append(DIGITS[0x0F & b]);
+        }
+    }
 
 	/*
 	 * (non-Javadoc)