src/be/nikiroo/utils/serial/SerialUtils.java

   1 package be.nikiroo.utils.serial;
   2
   3 import java.io.IOException;
   4 import java.io.InputStream;
   5 import java.io.NotSerializableException;
   6 import java.io.OutputStream;
   7 import java.lang.reflect.Array;
   8 import java.lang.reflect.Constructor;
   9 import java.lang.reflect.Field;
  10 import java.lang.reflect.Modifier;
  11 import java.net.URL;
  12 import java.util.ArrayList;
  13 import java.util.HashMap;
  14 import java.util.List;
  15 import java.util.Map;
  16 import java.util.UnknownFormatConversionException;
  17
  18 import be.nikiroo.utils.IOUtils;
  19 import be.nikiroo.utils.Image;
  20 import be.nikiroo.utils.StringUtils;
  21 import be.nikiroo.utils.streams.Base64InputStream;
  22 import be.nikiroo.utils.streams.Base64OutputStream;
  23 import be.nikiroo.utils.streams.BufferedInputStream;
  24 import be.nikiroo.utils.streams.NextableInputStream;
  25 import be.nikiroo.utils.streams.NextableInputStreamStep;
  26
  27 /**
  28  * Small class to help with serialisation.
  29  * <p>
  30  * Note that we do not support inner classes (but we do support nested classes)
  31  * and all objects require an empty constructor to be deserialised.
  32  * <p>
  33  * It is possible to add support to custom types (both the encoder and the
  34  * decoder will require the custom classes) -- see {@link CustomSerializer}.
  35  * <p>
  36  * Default supported types are:
  37  * <ul>
  38  * <li>NULL (as a null value)</li>
  39  * <li>String</li>
  40  * <li>Boolean</li>
  41  * <li>Byte</li>
  42  * <li>Character</li>
  43  * <li>Short</li>
  44  * <li>Long</li>
  45  * <li>Float</li>
  46  * <li>Double</li>
  47  * <li>Integer</li>
  48  * <li>Enum (any enum whose name and value is known by the caller)</li>
  49  * <li>java.awt.image.BufferedImage (as a {@link CustomSerializer})</li>
  50  * <li>An array of the above (as a {@link CustomSerializer})</li>
  51  * <li>URL</li>
  52  * </ul>
  53  *
  54  * @author niki
  55  */
  56 public class SerialUtils {
  57         private static Map<String, CustomSerializer> customTypes;
  58
  59         static {
  60                 customTypes = new HashMap<String, CustomSerializer>();
  61
  62                 // Array types:
  63                 customTypes.put("[]", new CustomSerializer() {
  64                         @Override
  65                         protected void toStream(OutputStream out, Object value)
  66                                         throws IOException {
  67
  68                                 String type = value.getClass().getCanonicalName();
  69                                 type = type.substring(0, type.length() - 2); // remove the []
  70
  71                                 write(out, type);
  72                                 try {
  73                                         for (int i = 0; true; i++) {
  74                                                 Object item = Array.get(value, i);
  75
  76                                                 // encode it normally if direct value
  77                                                 write(out, "\r");
  78                                                 if (!SerialUtils.encode(out, item)) {
  79                                                         try {
  80                                                                 write(out, "B64:");
  81                                                                 OutputStream out64 = new Base64OutputStream(
  82                                                                                 out, true);
  83                                                                 new Exporter(out64).append(item);
  84                                                                 out64.flush();
  85                                                         } catch (NotSerializableException e) {
  86                                                                 throw new UnknownFormatConversionException(e
  87                                                                                 .getMessage());
  88                                                         }
  89                                                 }
  90                                         }
  91                                 } catch (ArrayIndexOutOfBoundsException e) {
  92                                         // Done.
  93                                 }
  94                         }
  95
  96                         @Override
  97                         protected Object fromStream(InputStream in) throws IOException {
  98                                 NextableInputStream stream = new NextableInputStream(in,
  99                                                 new NextableInputStreamStep('\r'));
 100
 101                                 try {
 102                                         List<Object> list = new ArrayList<Object>();
 103                                         stream.next();
 104                                         String type = IOUtils.readSmallStream(stream);
 105
 106                                         while (stream.next()) {
 107                                                 Object value = new Importer().read(stream).getValue();
 108                                                 list.add(value);
 109                                         }
 110
 111                                         Object array = Array.newInstance(
 112                                                         SerialUtils.getClass(type), list.size());
 113                                         for (int i = 0; i < list.size(); i++) {
 114                                                 Array.set(array, i, list.get(i));
 115                                         }
 116
 117                                         return array;
 118                                 } catch (Exception e) {
 119                                         if (e instanceof IOException) {
 120                                                 throw (IOException) e;
 121                                         }
 122                                         throw new IOException(e.getMessage());
 123                                 }
 124                         }
 125
 126                         @Override
 127                         protected String getType() {
 128                                 return "[]";
 129                         }
 130                 });
 131
 132                 // URL:
 133                 customTypes.put("java.net.URL", new CustomSerializer() {
 134                         @Override
 135                         protected void toStream(OutputStream out, Object value)
 136                                         throws IOException {
 137                                 String val = "";
 138                                 if (value != null) {
 139                                         val = ((URL) value).toString();
 140                                 }
 141
 142                                 out.write(StringUtils.getBytes(val));
 143                         }
 144
 145                         @Override
 146                         protected Object fromStream(InputStream in) throws IOException {
 147                                 String val = IOUtils.readSmallStream(in);
 148                                 if (!val.isEmpty()) {
 149                                         return new URL(val);
 150                                 }
 151
 152                                 return null;
 153                         }
 154
 155                         @Override
 156                         protected String getType() {
 157                                 return "java.net.URL";
 158                         }
 159                 });
 160
 161                 // Images (this is currently the only supported image type by default)
 162                 customTypes.put("be.nikiroo.utils.Image", new CustomSerializer() {
 163                         @Override
 164                         protected void toStream(OutputStream out, Object value)
 165                                         throws IOException {
 166                                 Image img = (Image) value;
 167                                 OutputStream encoded = new Base64OutputStream(out, true);
 168                                 try {
 169                                         InputStream in = img.newInputStream();
 170                                         try {
 171                                                 IOUtils.write(in, encoded);
 172                                         } finally {
 173                                                 in.close();
 174                                         }
 175                                 } finally {
 176                                         encoded.flush();
 177                                         // Cannot close!
 178                                 }
 179                         }
 180
 181                         @Override
 182                         protected String getType() {
 183                                 return "be.nikiroo.utils.Image";
 184                         }
 185
 186                         @Override
 187                         protected Object fromStream(InputStream in) throws IOException {
 188                                 try {
 189                                         // Cannot close it!
 190                                         InputStream decoded = new Base64InputStream(in, false);
 191                                         return new Image(decoded);
 192                                 } catch (IOException e) {
 193                                         throw new UnknownFormatConversionException(e.getMessage());
 194                                 }
 195                         }
 196                 });
 197         }
 198
 199         /**
 200          * Create an empty object of the given type.
 201          *
 202          * @param type
 203          *            the object type (its class name)
 204          *
 205          * @return the new object
 206          *
 207          * @throws ClassNotFoundException
 208          *             if the class cannot be found
 209          * @throws NoSuchMethodException
 210          *             if the given class is not compatible with this code
 211          */
 212         public static Object createObject(String type)
 213                         throws ClassNotFoundException, NoSuchMethodException {
 214
 215                 String desc = null;
 216                 try {
 217                         Class<?> clazz = getClass(type);
 218                         String className = clazz.getName();
 219                         List<Object> args = new ArrayList<Object>();
 220                         List<Class<?>> classes = new ArrayList<Class<?>>();
 221                         Constructor<?> ctor = null;
 222                         if (className.contains("$")) {
 223                                 for (String parentName = className.substring(0,
 224                                                 className.lastIndexOf('$'));; parentName = parentName
 225                                                 .substring(0, parentName.lastIndexOf('$'))) {
 226                                         Object parent = createObject(parentName);
 227                                         args.add(parent);
 228                                         classes.add(parent.getClass());
 229
 230                                         if (!parentName.contains("$")) {
 231                                                 break;
 232                                         }
 233                                 }
 234
 235                                 // Better error description in case there is no empty
 236                                 // constructor:
 237                                 desc = "";
 238                                 String end = "";
 239                                 for (Class<?> parent = clazz; parent != null
 240                                                 && !parent.equals(Object.class); parent = parent
 241                                                 .getSuperclass()) {
 242                                         if (!desc.isEmpty()) {
 243                                                 desc += " [:";
 244                                                 end += "]";
 245                                         }
 246                                         desc += parent;
 247                                 }
 248                                 desc += end;
 249                                 //
 250
 251                                 try {
 252                                         ctor = clazz.getDeclaredConstructor(classes
 253                                                         .toArray(new Class[] {}));
 254                                 } catch (NoSuchMethodException nsme) {
 255                                         // TODO: it seems we do not always need a parameter for each
 256                                         // level, so we currently try "ALL" levels or "FIRST" level
 257                                         // only -> we should check the actual rule and use it
 258                                         ctor = clazz.getDeclaredConstructor(classes.get(0));
 259                                         Object firstParent = args.get(0);
 260                                         args.clear();
 261                                         args.add(firstParent);
 262                                 }
 263                                 desc = null;
 264                         } else {
 265                                 ctor = clazz.getDeclaredConstructor();
 266                         }
 267
 268                         ctor.setAccessible(true);
 269                         return ctor.newInstance(args.toArray());
 270                 } catch (ClassNotFoundException e) {
 271                         throw e;
 272                 } catch (NoSuchMethodException e) {
 273                         if (desc != null) {
 274                                 throw new NoSuchMethodException("Empty constructor not found: "
 275                                                 + desc);
 276                         }
 277                         throw e;
 278                 } catch (Exception e) {
 279                         throw new NoSuchMethodException("Cannot instantiate: " + type);
 280                 }
 281         }
 282
 283         /**
 284          * Insert a custom serialiser that will take precedence over the default one
 285          * or the target class.
 286          *
 287          * @param serializer
 288          *            the custom serialiser
 289          */
 290         static public void addCustomSerializer(CustomSerializer serializer) {
 291                 customTypes.put(serializer.getType(), serializer);
 292         }
 293
 294         /**
 295          * Serialise the given object into this {@link OutputStream}.
 296          * <p>
 297          * <b>Important: </b>If the operation fails (with a
 298          * {@link NotSerializableException}), the {@link StringBuilder} will be
 299          * corrupted (will contain bad, most probably not importable data).
 300          *
 301          * @param out
 302          *            the output {@link OutputStream} to serialise to
 303          * @param o
 304          *            the object to serialise
 305          * @param map
 306          *            the map of already serialised objects (if the given object or
 307          *            one of its descendant is already present in it, only an ID
 308          *            will be serialised)
 309          *
 310          * @throws NotSerializableException
 311          *             if the object cannot be serialised (in this case, the
 312          *             {@link StringBuilder} can contain bad, most probably not
 313          *             importable data)
 314          * @throws IOException
 315          *             in case of I/O errors
 316          */
 317         static void append(OutputStream out, Object o, Map<Integer, Object> map)
 318                         throws NotSerializableException, IOException {
 319
 320                 Field[] fields = new Field[] {};
 321                 String type = "";
 322                 String id = "NULL";
 323
 324                 if (o != null) {
 325                         int hash = System.identityHashCode(o);
 326                         fields = o.getClass().getDeclaredFields();
 327                         type = o.getClass().getCanonicalName();
 328                         if (type == null) {
 329                                 // Anonymous inner classes support
 330                                 type = o.getClass().getName();
 331                         }
 332                         id = Integer.toString(hash);
 333                         if (map.containsKey(hash)) {
 334                                 fields = new Field[] {};
 335                         } else {
 336                                 map.put(hash, o);
 337                         }
 338                 }
 339
 340                 write(out, "{\nREF ");
 341                 write(out, type);
 342                 write(out, "@");
 343                 write(out, id);
 344                 write(out, ":");
 345
 346                 if (!encode(out, o)) { // check if direct value
 347                         try {
 348                                 for (Field field : fields) {
 349                                         field.setAccessible(true);
 350
 351                                         if (field.getName().startsWith("this$")
 352                                                         || field.isSynthetic()
 353                                                         || (field.getModifiers() & Modifier.STATIC) == Modifier.STATIC) {
 354                                                 // Do not keep this links of nested classes
 355                                                 // Do not keep synthetic fields
 356                                                 // Do not keep final fields
 357                                                 continue;
 358                                         }
 359
 360                                         write(out, "\n^");
 361                                         write(out, field.getName());
 362                                         write(out, ":");
 363
 364                                         Object value = field.get(o);
 365
 366                                         if (!encode(out, value)) {
 367                                                 write(out, "\n");
 368                                                 append(out, value, map);
 369                                         }
 370                                 }
 371                         } catch (IllegalArgumentException e) {
 372                                 e.printStackTrace(); // should not happen (see
 373                                                                                 // setAccessible)
 374                         } catch (IllegalAccessException e) {
 375                                 e.printStackTrace(); // should not happen (see
 376                                                                                 // setAccessible)
 377                         }
 378
 379                         write(out, "\n}");
 380                 }
 381         }
 382
 383         /**
 384          * Encode the object into the given {@link OutputStream} if possible and if
 385          * supported.
 386          * <p>
 387          * A supported object in this context means an object we can directly
 388          * encode, like an Integer or a String. Custom objects and arrays are also
 389          * considered supported, but <b>compound objects are not supported here</b>.
 390          * <p>
 391          * For compound objects, you should use {@link Exporter}.
 392          *
 393          * @param out
 394          *            the {@link OutputStream} to append to
 395          * @param value
 396          *            the object to encode (can be NULL, which will be encoded)
 397          *
 398          * @return TRUE if success, FALSE if not (the content of the
 399          *         {@link OutputStream} won't be changed in case of failure)
 400          *
 401          * @throws IOException
 402          *             in case of I/O error
 403          */
 404         static boolean encode(OutputStream out, Object value) throws IOException {
 405                 if (value == null) {
 406                         write(out, "NULL");
 407                 } else if (value.getClass().getSimpleName().endsWith("[]")) {
 408                         // Simple name does support [] suffix and do not return NULL for
 409                         // inner anonymous classes
 410                         customTypes.get("[]").encode(out, value);
 411                 } else if (customTypes.containsKey(value.getClass().getCanonicalName())) {
 412                         customTypes.get(value.getClass().getCanonicalName())//
 413                                         .encode(out, value);
 414                 } else if (value instanceof String) {
 415                         encodeString(out, (String) value);
 416                 } else if (value instanceof Boolean) {
 417                         write(out, value);
 418                 } else if (value instanceof Byte) {
 419                         write(out, "b");
 420                         write(out, value);
 421                 } else if (value instanceof Character) {
 422                         write(out, "c");
 423                         encodeString(out, "" + value);
 424                 } else if (value instanceof Short) {
 425                         write(out, "s");
 426                         write(out, value);
 427                 } else if (value instanceof Integer) {
 428                         write(out, "i");
 429                         write(out, value);
 430                 } else if (value instanceof Long) {
 431                         write(out, "l");
 432                         write(out, value);
 433                 } else if (value instanceof Float) {
 434                         write(out, "f");
 435                         write(out, value);
 436                 } else if (value instanceof Double) {
 437                         write(out, "d");
 438                         write(out, value);
 439                 } else if (value instanceof Enum) {
 440                         write(out, "E:");
 441                         String type = value.getClass().getCanonicalName();
 442                         write(out, type);
 443                         write(out, ".");
 444                         write(out, ((Enum<?>) value).name());
 445                         write(out, ";");
 446                 } else {
 447                         return false;
 448                 }
 449
 450                 return true;
 451         }
 452
 453         static boolean isDirectValue(BufferedInputStream encodedValue)
 454                         throws IOException {
 455                 if (CustomSerializer.isCustom(encodedValue)) {
 456                         return false;
 457                 }
 458
 459                 for (String fullValue : new String[] { "NULL", "null", "true", "false" }) {
 460                         if (encodedValue.is(fullValue)) {
 461                                 return true;
 462                         }
 463                 }
 464
 465                 for (String prefix : new String[] { "c\"", "\"", "b", "s", "i", "l",
 466                                 "f", "d", "E:" }) {
 467                         if (encodedValue.startsWith(prefix)) {
 468                                 return true;
 469                         }
 470                 }
 471
 472                 return false;
 473         }
 474
 475         /**
 476          * Decode the data into an equivalent supported source object.
 477          * <p>
 478          * A supported object in this context means an object we can directly
 479          * encode, like an Integer or a String (see
 480          * {@link SerialUtils#decode(String)}.
 481          * <p>
 482          * Custom objects and arrays are also considered supported here, but
 483          * <b>compound objects are not</b>.
 484          * <p>
 485          * For compound objects, you should use {@link Importer}.
 486          *
 487          * @param encodedValue
 488          *            the encoded data, cannot be NULL
 489          *
 490          * @return the object (can be NULL for NULL encoded values)
 491          *
 492          * @throws IOException
 493          *             if the content cannot be converted
 494          */
 495         static Object decode(BufferedInputStream encodedValue) throws IOException {
 496                 if (CustomSerializer.isCustom(encodedValue)) {
 497                         // custom^TYPE^ENCODED_VALUE
 498                         NextableInputStream content = new NextableInputStream(encodedValue,
 499                                         new NextableInputStreamStep('^'));
 500                         try {
 501                                 content.next();
 502                                 @SuppressWarnings("unused")
 503                                 String custom = IOUtils.readSmallStream(content);
 504                                 content.next();
 505                                 String type = IOUtils.readSmallStream(content);
 506                                 content.nextAll();
 507                                 if (customTypes.containsKey(type)) {
 508                                         return customTypes.get(type).decode(content);
 509                                 }
 510                                 content.end();
 511                                 throw new IOException("Unknown custom type: " + type);
 512                         } finally {
 513                                 content.close(false);
 514                                 // TODO: check what happens with thrown Exception in finally
 515                                 encodedValue.end();
 516                         }
 517                 }
 518
 519                 String encodedString = IOUtils.readSmallStream(encodedValue);
 520                 return decode(encodedString);
 521         }
 522
 523         /**
 524          * Decode the data into an equivalent supported source object.
 525          * <p>
 526          * A supported object in this context means an object we can directly
 527          * encode, like an Integer or a String.
 528          * <p>
 529          * For custom objects and arrays, you should use
 530          * {@link SerialUtils#decode(InputStream)} or directly {@link Importer}.
 531          * <p>
 532          * For compound objects, you should use {@link Importer}.
 533          *
 534          * @param encodedValue
 535          *            the encoded data, cannot be NULL
 536          *
 537          * @return the object (can be NULL for NULL encoded values)
 538          *
 539          * @throws IOException
 540          *             if the content cannot be converted
 541          */
 542         static Object decode(String encodedValue) throws IOException {
 543                 try {
 544                         String cut = "";
 545                         if (encodedValue.length() > 1) {
 546                                 cut = encodedValue.substring(1);
 547                         }
 548
 549                         if (encodedValue.equals("NULL") || encodedValue.equals("null")) {
 550                                 return null;
 551                         } else if (encodedValue.startsWith("\"")) {
 552                                 return decodeString(encodedValue);
 553                         } else if (encodedValue.equals("true")) {
 554                                 return true;
 555                         } else if (encodedValue.equals("false")) {
 556                                 return false;
 557                         } else if (encodedValue.startsWith("b")) {
 558                                 return Byte.parseByte(cut);
 559                         } else if (encodedValue.startsWith("c")) {
 560                                 return decodeString(cut).charAt(0);
 561                         } else if (encodedValue.startsWith("s")) {
 562                                 return Short.parseShort(cut);
 563                         } else if (encodedValue.startsWith("l")) {
 564                                 return Long.parseLong(cut);
 565                         } else if (encodedValue.startsWith("f")) {
 566                                 return Float.parseFloat(cut);
 567                         } else if (encodedValue.startsWith("d")) {
 568                                 return Double.parseDouble(cut);
 569                         } else if (encodedValue.startsWith("i")) {
 570                                 return Integer.parseInt(cut);
 571                         } else if (encodedValue.startsWith("E:")) {
 572                                 cut = cut.substring(1);
 573                                 return decodeEnum(cut);
 574                         } else {
 575                                 throw new IOException("Unrecognized value: " + encodedValue);
 576                         }
 577                 } catch (Exception e) {
 578                         if (e instanceof IOException) {
 579                                 throw (IOException) e;
 580                         }
 581                         throw new IOException(e.getMessage(), e);
 582                 }
 583         }
 584
 585         /**
 586          * Write the given {@link String} into the given {@link OutputStream} in
 587          * UTF-8.
 588          *
 589          * @param out
 590          *            the {@link OutputStream}
 591          * @param data
 592          *            the data to write, cannot be NULL
 593          *
 594          * @throws IOException
 595          *             in case of I/O error
 596          */
 597         static void write(OutputStream out, Object data) throws IOException {
 598                 out.write(StringUtils.getBytes(data.toString()));
 599         }
 600
 601         /**
 602          * Return the corresponding class or throw an {@link Exception} if it
 603          * cannot.
 604          *
 605          * @param type
 606          *            the class name to look for
 607          *
 608          * @return the class (will never be NULL)
 609          *
 610          * @throws ClassNotFoundException
 611          *             if the class cannot be found
 612          * @throws NoSuchMethodException
 613          *             if the class cannot be created (usually because it or its
 614          *             enclosing class doesn't have an empty constructor)
 615          */
 616         static private Class<?> getClass(String type)
 617                         throws ClassNotFoundException, NoSuchMethodException {
 618                 Class<?> clazz = null;
 619                 try {
 620                         clazz = Class.forName(type);
 621                 } catch (ClassNotFoundException e) {
 622                         int pos = type.length();
 623                         pos = type.lastIndexOf(".", pos);
 624                         if (pos >= 0) {
 625                                 String parentType = type.substring(0, pos);
 626                                 String nestedType = type.substring(pos + 1);
 627                                 Class<?> javaParent = null;
 628                                 try {
 629                                         javaParent = getClass(parentType);
 630                                         parentType = javaParent.getName();
 631                                         clazz = Class.forName(parentType + "$" + nestedType);
 632                                 } catch (Exception ee) {
 633                                 }
 634
 635                                 if (javaParent == null) {
 636                                         throw new NoSuchMethodException(
 637                                                         "Class not found: "
 638                                                                         + type
 639                                                                         + " (the enclosing class cannot be created: maybe it doesn't have an empty constructor?)");
 640                                 }
 641                         }
 642                 }
 643
 644                 if (clazz == null) {
 645                         throw new ClassNotFoundException("Class not found: " + type);
 646                 }
 647
 648                 return clazz;
 649         }
 650
 651         @SuppressWarnings({ "unchecked", "rawtypes" })
 652         static private Enum<?> decodeEnum(String escaped) {
 653                 // escaped: be.xxx.EnumType.VALUE;
 654                 int pos = escaped.lastIndexOf(".");
 655                 String type = escaped.substring(0, pos);
 656                 String name = escaped.substring(pos + 1, escaped.length() - 1);
 657
 658                 try {
 659                         return Enum.valueOf((Class<Enum>) getClass(type), name);
 660                 } catch (Exception e) {
 661                         throw new UnknownFormatConversionException("Unknown enum: <" + type
 662                                         + "> " + name);
 663                 }
 664         }
 665
 666         // aa bb -> "aa\tbb"
 667         static void encodeString(OutputStream out, String raw) throws IOException {
 668                 // TODO: not. efficient.
 669                 out.write('\"');
 670                 for (char car : raw.toCharArray()) {
 671                         encodeString(out, car);
 672                 }
 673                 out.write('\"');
 674         }
 675
 676         // for encoding string, NOT to encode a char by itself!
 677         static void encodeString(OutputStream out, char raw) throws IOException {
 678                 switch (raw) {
 679                 case '\\':
 680                         out.write('\\');
 681                         out.write('\\');
 682                         break;
 683                 case '\r':
 684                         out.write('\\');
 685                         out.write('r');
 686                         break;
 687                 case '\n':
 688                         out.write('\\');
 689                         out.write('n');
 690                         break;
 691                 case '"':
 692                         out.write('\\');
 693                         out.write('\"');
 694                         break;
 695                 default:
 696                         out.write(raw);
 697                         break;
 698                 }
 699         }
 700
 701         // "aa\tbb" -> aa bb
 702         static String decodeString(String escaped) {
 703                 StringBuilder builder = new StringBuilder();
 704
 705                 boolean escaping = false;
 706                 for (char car : escaped.toCharArray()) {
 707                         if (!escaping) {
 708                                 if (car == '\\') {
 709                                         escaping = true;
 710                                 } else {
 711                                         builder.append(car);
 712                                 }
 713                         } else {
 714                                 switch (car) {
 715                                 case '\\':
 716                                         builder.append('\\');
 717                                         break;
 718                                 case 'r':
 719                                         builder.append('\r');
 720                                         break;
 721                                 case 'n':
 722                                         builder.append('\n');
 723                                         break;
 724                                 case '"':
 725                                         builder.append('"');
 726                                         break;
 727                                 }
 728                                 escaping = false;
 729                         }
 730                 }
 731
 732                 return builder.substring(1, builder.length() - 1);
 733         }
 734 }