Java tutorial
package com.fasterxml.jackson.databind.deser.std; import java.io.IOException; import java.util.Arrays; import java.util.UUID; import com.fasterxml.jackson.core.Base64Variants; import com.fasterxml.jackson.databind.DeserializationContext; public class UUIDDeserializer extends FromStringDeserializer<UUID> { private static final long serialVersionUID = 1L; final static int[] HEX_DIGITS = new int[127]; static { Arrays.fill(HEX_DIGITS, -1); for (int i = 0; i < 10; ++i) { HEX_DIGITS['0' + i] = i; } for (int i = 0; i < 6; ++i) { HEX_DIGITS['a' + i] = 10 + i; HEX_DIGITS['A' + i] = 10 + i; } } public UUIDDeserializer() { super(UUID.class); } @Override protected UUID _deserialize(String id, DeserializationContext ctxt) throws IOException { // Adapted from java-uuid-generator (https://github.com/cowtowncoder/java-uuid-generator) // which is 5x faster than UUID.fromString(value), as oper "ManualReadPerfWithUUID" if (id.length() != 36) { /* 14-Sep-2013, tatu: One trick we do allow, Base64-encoding, since we know * length it must have... */ if (id.length() == 24) { byte[] stuff = Base64Variants.getDefaultVariant().decode(id); return _fromBytes(stuff, ctxt); } _badFormat(id); } // verify hyphens first: if ((id.charAt(8) != '-') || (id.charAt(13) != '-') || (id.charAt(18) != '-') || (id.charAt(23) != '-')) { _badFormat(id); } long l1 = intFromChars(id, 0); l1 <<= 32; long l2 = ((long) shortFromChars(id, 9)) << 16; l2 |= shortFromChars(id, 14); long hi = l1 + l2; int i1 = (shortFromChars(id, 19) << 16) | shortFromChars(id, 24); l1 = i1; l1 <<= 32; l2 = intFromChars(id, 28); l2 = (l2 << 32) >>> 32; // sign removal, Java-style. Ugh. long lo = l1 | l2; return new UUID(hi, lo); } @Override protected UUID _deserializeEmbedded(Object ob, DeserializationContext ctxt) throws IOException { if (ob instanceof byte[]) { return _fromBytes((byte[]) ob, ctxt); } super._deserializeEmbedded(ob, ctxt); return null; // never gets here } private void _badFormat(String uuidStr) { throw new NumberFormatException("UUID has to be represented by the standard 36-char representation"); } static int intFromChars(String str, int index) { return (byteFromChars(str, index) << 24) + (byteFromChars(str, index + 2) << 16) + (byteFromChars(str, index + 4) << 8) + byteFromChars(str, index + 6); } static int shortFromChars(String str, int index) { return (byteFromChars(str, index) << 8) + byteFromChars(str, index + 2); } static int byteFromChars(String str, int index) { final char c1 = str.charAt(index); final char c2 = str.charAt(index + 1); if (c1 <= 127 && c2 <= 127) { int hex = (HEX_DIGITS[c1] << 4) | HEX_DIGITS[c2]; if (hex >= 0) { return hex; } } if (c1 > 127 || HEX_DIGITS[c1] < 0) { return _badChar(str, index, c1); } return _badChar(str, index + 1, c2); } static int _badChar(String uuidStr, int index, char c) { throw new NumberFormatException("Non-hex character '" + c + "', not valid character for a UUID String" + "' (value 0x" + Integer.toHexString(c) + ") for UUID String \"" + uuidStr + "\""); } private UUID _fromBytes(byte[] bytes, DeserializationContext ctxt) throws IOException { if (bytes.length != 16) { ctxt.mappingException("Can only construct UUIDs from byte[16]; got " + bytes.length + " bytes"); } return new UUID(_long(bytes, 0), _long(bytes, 8)); } private static long _long(byte[] b, int offset) { long l1 = ((long) _int(b, offset)) << 32; long l2 = _int(b, offset + 4); // faster to just do it than check if it has sign l2 = (l2 << 32) >>> 32; // to get rid of sign return l1 | l2; } private static int _int(byte[] b, int offset) { return (b[offset] << 24) | ((b[offset + 1] & 0xFF) << 16) | ((b[offset + 2] & 0xFF) << 8) | (b[offset + 3] & 0xFF); } }