Java tutorial
/* * Copyright (C) 2011 Google Inc. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.cardinity.json; import com.google.gson.JsonParseException; import com.google.gson.TypeAdapter; import com.google.gson.stream.JsonReader; import com.google.gson.stream.JsonWriter; import java.io.IOException; import java.text.ParseException; import java.text.ParsePosition; import java.util.*; public final class UtcDateTypeAdapter extends TypeAdapter<Date> { private final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone("UTC"); @Override public void write(JsonWriter out, Date date) throws IOException { if (date == null) { out.nullValue(); } else { String value = format(date, true, UTC_TIME_ZONE); out.value(value); } } @Override public Date read(JsonReader in) throws IOException { try { switch (in.peek()) { case NULL: in.nextNull(); return null; default: String date = in.nextString(); // Instead of using iso8601Format.parse(value), we use Jackson's date parsing // This is because Android doesn't support XXX because it is JDK 1.6 return parse(date, new ParsePosition(0)); } } catch (ParseException e) { throw new JsonParseException(e); } } // Date parsing code from Jackson databind ISO8601Utils.java // https://github.com/FasterXML/jackson-databind/blob/master/src/main/java/com/fasterxml/jackson/databind/util // /ISO8601Utils.java private static final String GMT_ID = "GMT"; /** * Format date into yyyy-MM-ddThh:mm:ss[.sss][Z|[+-]hh:mm] * * @param date the date to format * @param millis true to include millis precision otherwise false * @param tz timezone to use for the formatting (GMT will produce 'Z') * @return the date formatted as yyyy-MM-ddThh:mm:ss[.sss][Z|[+-]hh:mm] */ private static String format(Date date, boolean millis, TimeZone tz) { Calendar calendar = new GregorianCalendar(tz, Locale.US); calendar.setTime(date); // estimate capacity of buffer as close as we can (yeah, that's pedantic ;) int capacity = "yyyy-MM-ddThh:mm:ss".length(); capacity += millis ? ".sss".length() : 0; capacity += tz.getRawOffset() == 0 ? "Z".length() : "+hh:mm".length(); StringBuilder formatted = new StringBuilder(capacity); padInt(formatted, calendar.get(Calendar.YEAR), "yyyy".length()); formatted.append('-'); padInt(formatted, calendar.get(Calendar.MONTH) + 1, "MM".length()); formatted.append('-'); padInt(formatted, calendar.get(Calendar.DAY_OF_MONTH), "dd".length()); formatted.append('T'); padInt(formatted, calendar.get(Calendar.HOUR_OF_DAY), "hh".length()); formatted.append(':'); padInt(formatted, calendar.get(Calendar.MINUTE), "mm".length()); formatted.append(':'); padInt(formatted, calendar.get(Calendar.SECOND), "ss".length()); if (millis) { formatted.append('.'); padInt(formatted, calendar.get(Calendar.MILLISECOND), "sss".length()); } int offset = tz.getOffset(calendar.getTimeInMillis()); if (offset != 0) { int hours = Math.abs((offset / (60 * 1000)) / 60); int minutes = Math.abs((offset / (60 * 1000)) % 60); formatted.append(offset < 0 ? '-' : '+'); padInt(formatted, hours, "hh".length()); formatted.append(':'); padInt(formatted, minutes, "mm".length()); } else { formatted.append('Z'); } return formatted.toString(); } /** * Zero pad a number to a specified length * * @param buffer buffer to use for padding * @param value the integer value to pad if necessary. * @param length the length of the string we should zero pad */ private static void padInt(StringBuilder buffer, int value, int length) { String strValue = Integer.toString(value); for (int i = length - strValue.length(); i > 0; i--) { buffer.append('0'); } buffer.append(strValue); } /** * Parse a date from ISO-8601 formatted string. It expects a format * [yyyy-MM-dd|yyyyMMdd][T(hh:mm[:ss[.sss]]|hhmm[ss[.sss]])]?[Z|[+-]hh:mm]] * * @param date ISO string to parse in the appropriate format. * @param pos The position to start parsing from, updated to where parsing stopped. * @return the parsed date * @throws ParseException if the date is not in the appropriate format */ private static Date parse(String date, ParsePosition pos) throws ParseException { Exception fail; try { int offset = pos.getIndex(); // extract year int year = parseInt(date, offset, offset += 4); if (checkOffset(date, offset, '-')) { offset += 1; } // extract month int month = parseInt(date, offset, offset += 2); if (checkOffset(date, offset, '-')) { offset += 1; } // extract day int day = parseInt(date, offset, offset += 2); // default time value int hour = 0; int minutes = 0; int seconds = 0; int milliseconds = 0; // always use 0 otherwise returned date will include millis of current time if (checkOffset(date, offset, 'T')) { // extract hours, minutes, seconds and milliseconds hour = parseInt(date, offset += 1, offset += 2); if (checkOffset(date, offset, ':')) { offset += 1; } minutes = parseInt(date, offset, offset += 2); if (checkOffset(date, offset, ':')) { offset += 1; } // second and milliseconds can be optional if (date.length() > offset) { char c = date.charAt(offset); if (c != 'Z' && c != '+' && c != '-') { seconds = parseInt(date, offset, offset += 2); // milliseconds can be optional in the format if (checkOffset(date, offset, '.')) { int count = 1; while (!checkOffset(date, offset + count, 'Z') && count < 4) count++; milliseconds = parseInt(date, offset + 1, offset += count); } } } } // extract timezone String timezoneId; if (date.length() <= offset) { throw new IllegalArgumentException("No time zone indicator"); } char timezoneIndicator = date.charAt(offset); if (timezoneIndicator == '+' || timezoneIndicator == '-') { String timezoneOffset = date.substring(offset); timezoneId = GMT_ID + timezoneOffset; offset += timezoneOffset.length(); } else if (timezoneIndicator == 'Z') { timezoneId = GMT_ID; offset += 1; } else { throw new IndexOutOfBoundsException("Invalid time zone indicator " + timezoneIndicator); } TimeZone timezone = TimeZone.getTimeZone(timezoneId); if (!timezone.getID().equals(timezoneId)) { throw new IndexOutOfBoundsException(); } Calendar calendar = new GregorianCalendar(timezone); calendar.setLenient(false); calendar.set(Calendar.YEAR, year); calendar.set(Calendar.MONTH, month - 1); calendar.set(Calendar.DAY_OF_MONTH, day); calendar.set(Calendar.HOUR_OF_DAY, hour); calendar.set(Calendar.MINUTE, minutes); calendar.set(Calendar.SECOND, seconds); calendar.set(Calendar.MILLISECOND, milliseconds); pos.setIndex(offset); return calendar.getTime(); // If we get a ParseException it'll already have the right message/offset. // Other exception types can convert here. } catch (IndexOutOfBoundsException e) { fail = e; } catch (NumberFormatException e) { fail = e; } catch (IllegalArgumentException e) { fail = e; } String input = (date == null) ? null : ('"' + date + "'"); throw new ParseException("Failed to parse date [" + input + "]: " + fail.getMessage(), pos.getIndex()); } /** * Check if the expected character exist at the given offset in the value. * * @param value the string to check at the specified offset * @param offset the offset to look for the expected character * @param expected the expected character * @return true if the expected character exist at the given offset */ private static boolean checkOffset(String value, int offset, char expected) { return (offset < value.length()) && (value.charAt(offset) == expected); } /** * Parse an integer located between 2 given offsets in a string * * @param value the string to parse * @param beginIndex the start index for the integer in the string * @param endIndex the end index for the integer in the string * @return the int * @throws NumberFormatException if the value is not a number */ private static int parseInt(String value, int beginIndex, int endIndex) throws NumberFormatException { if (beginIndex < 0 || endIndex > value.length() || beginIndex > endIndex) { throw new NumberFormatException(value); } // use same logic as in Integer.parseInt() but less generic we're not supporting negative values int i = beginIndex; int result = 0; int digit; if (i < endIndex) { digit = Character.digit(value.charAt(i++), 10); if (digit < 0) { throw new NumberFormatException("Invalid number: " + value); } result = -digit; } while (i < endIndex) { digit = Character.digit(value.charAt(i++), 10); if (digit < 0) { throw new NumberFormatException("Invalid number: " + value); } result *= 10; result -= digit; } return -result; } }