Java tutorial
/* * Copyright 2008-present MongoDB, 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.mongodb.util; import org.bson.BSONCallback; /** * Helper methods for JSON serialization and de-serialization * * @see org.bson.json.JsonReader * @see org.bson.json.JsonWriter * @see com.mongodb.BasicDBObject#toJson() * @see com.mongodb.BasicDBObject#parse(String) * * @deprecated This class has been superseded by to toJson and parse methods on BasicDBObject */ @Deprecated @SuppressWarnings("deprecation") public class JSON { /** * <p>Serializes an object into its JSON form.</p> * * <p>This method delegates serialization to {@code JSONSerializers.getLegacy}</p> * * @param object object to serialize * @return String containing JSON form of the object * @see JSONSerializers#getLegacy() */ public static String serialize(final Object object) { StringBuilder buf = new StringBuilder(); serialize(object, buf); return buf.toString(); } /** * <p>Serializes an object into its JSON form.</p> * * <p>This method delegates serialization to {@code JSONSerializers.getLegacy}</p> * * @param object object to serialize * @param buf StringBuilder containing the JSON representation under construction * @see JSONSerializers#getLegacy() */ public static void serialize(final Object object, final StringBuilder buf) { JSONSerializers.getLegacy().serialize(object, buf); } /** * <p>Parses a JSON string and returns a corresponding Java object. The returned value is either a {@link com.mongodb.DBObject DBObject} * (if the string is a JSON object or array), or a boxed primitive value according to the following mapping:</p> * <ul> * <li>{@code java.lang.Boolean} for {@code true} or {@code false}</li> * <li>{@code java.lang.Integer} for integers between Integer.MIN_VALUE and Integer.MAX_VALUE</li> * <li>{@code java.lang.Long} for integers outside of this range</li> * <li>{@code java.lang.Double} for floating point numbers</li> * </ul> * If the parameter is a string that contains a single-quoted or double-quoted string, it is returned as an unquoted {@code * java.lang.String}. Parses a JSON string representing a JSON value * * @param jsonString the string to parse * @return a Java object representing the JSON data * @throws JSONParseException if jsonString is not valid JSON */ public static Object parse(final String jsonString) { return parse(jsonString, null); } /** * Parses a JSON string and constructs a corresponding Java object by calling the methods of a {@link org.bson.BSONCallback * BSONCallback} during parsing. If the callback {@code c} is null, this method is equivalent to {@link JSON#parse(String) * parse(String)}. * * @param s the string to parse * @param c the BSONCallback to call during parsing * @return a Java object representing the JSON data * @throws JSONParseException if s is not valid JSON */ public static Object parse(final String s, final BSONCallback c) { if (s == null || (s.trim()).equals("")) { return null; } JSONParser p = new JSONParser(s, c); return p.parse(); } static void string(final StringBuilder a, final String s) { a.append("\""); for (int i = 0; i < s.length(); ++i) { char c = s.charAt(i); if (c == '\\') { a.append("\\\\"); } else if (c == '"') { a.append("\\\""); } else if (c == '\n') { a.append("\\n"); } else if (c == '\r') { a.append("\\r"); } else if (c == '\t') { a.append("\\t"); } else if (c == '\b') { a.append("\\b"); } else if (c < 32) { continue; } else { a.append(c); } } a.append("\""); } } /** * <p>Parser for JSON objects.</p> * * <p>Supports all types described at www.json.org, except for numbers with "e" or "E" in them.</p> */ class JSONParser { final String s; int pos = 0; final BSONCallback _callback; JSONParser(final String s) { this(s, null); } @SuppressWarnings("deprecation") JSONParser(final String s, final BSONCallback callback) { this.s = s; _callback = (callback == null) ? new JSONCallback() : callback; } /** * Parse an unknown type. * * @return Object the next item * @throws JSONParseException if invalid JSON is found */ public Object parse() { return parse(null); } /** * Parse an unknown type. * * @return Object the next item * @throws JSONParseException if invalid JSON is found */ protected Object parse(final String name) { Object value = null; char current = get(); switch (current) { // null case 'n': read('n'); read('u'); read('l'); read('l'); value = null; break; // NaN case 'N': read('N'); read('a'); read('N'); value = Double.NaN; break; // true case 't': read('t'); read('r'); read('u'); read('e'); value = true; break; // false case 'f': read('f'); read('a'); read('l'); read('s'); read('e'); value = false; break; // string case '\'': case '\"': value = parseString(true); break; // number case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': case '+': case '-': value = parseNumber(); break; // array case '[': value = parseArray(name); break; // object case '{': value = parseObject(name); break; default: throw new JSONParseException(s, pos); } return value; } /** * Parses an object for the form <i>{}</i> and <i>{ members }</i>. * * @return DBObject the next object * @throws JSONParseException if invalid JSON is found */ public Object parseObject() { return parseObject(null); } /** * Parses an object for the form <i>{}</i> and <i>{ members }</i>. * * @return DBObject the next object * @throws JSONParseException if invalid JSON is found */ protected Object parseObject(final String name) { if (name != null) { _callback.objectStart(name); } else { _callback.objectStart(); } read('{'); char current = get(); while (get() != '}') { String key = parseString(false); read(':'); Object value = parse(key); doCallback(key, value); if ((current = get()) == ',') { read(','); } else { break; } } read('}'); return _callback.objectDone(); } protected void doCallback(final String name, final Object value) { if (value == null) { _callback.gotNull(name); } else if (value instanceof String) { _callback.gotString(name, (String) value); } else if (value instanceof Boolean) { _callback.gotBoolean(name, (Boolean) value); } else if (value instanceof Integer) { _callback.gotInt(name, (Integer) value); } else if (value instanceof Long) { _callback.gotLong(name, (Long) value); } else if (value instanceof Double) { _callback.gotDouble(name, (Double) value); } } /** * Read the current character, making sure that it is the expected character. Advances the pointer to the next character. * * @param ch the character expected * @throws JSONParseException if the current character does not match the given character */ public void read(final char ch) { if (!check(ch)) { throw new JSONParseException(s, pos); } pos++; } public char read() { if (pos >= s.length()) { throw new IllegalStateException("string done"); } return s.charAt(pos++); } /** * Read the current character, making sure that it is a hexidecimal character. * * @throws JSONParseException if the current character is not a hexidecimal character */ public void readHex() { if (pos < s.length() && ((s.charAt(pos) >= '0' && s.charAt(pos) <= '9') || (s.charAt(pos) >= 'A' && s.charAt(pos) <= 'F') || (s.charAt(pos) >= 'a' && s.charAt(pos) <= 'f'))) { pos++; } else { throw new JSONParseException(s, pos); } } /** * Checks the current character, making sure that it is the expected character. * * @param ch the character expected * @throws JSONParseException if the current character does not match the given character */ public boolean check(final char ch) { return get() == ch; } /** * Advances the position in the string past any whitespace. */ public void skipWS() { while (pos < s.length() && Character.isWhitespace(s.charAt(pos))) { pos++; } } /** * Returns the current character. Returns -1 if there are no more characters. * * @return the next character */ public char get() { skipWS(); if (pos < s.length()) { return s.charAt(pos); } return (char) -1; } /** * Parses a string. * * @return the next string. * @throws JSONParseException if invalid JSON is found */ public String parseString(final boolean needQuote) { char quot = 0; if (check('\'')) { quot = '\''; } else if (check('\"')) { quot = '\"'; } else if (needQuote) { throw new JSONParseException(s, pos); } char current; if (quot > 0) { read(quot); } StringBuilder buf = new StringBuilder(); int start = pos; while (pos < s.length()) { current = s.charAt(pos); if (quot > 0) { if (current == quot) { break; } } else { if (current == ':' || current == ' ') { break; } } if (current == '\\') { pos++; char x = get(); char special = 0; //CHECKSTYLE:OFF switch (x) { case 'u': // decode unicode buf.append(s.substring(start, pos - 1)); pos++; int tempPos = pos; readHex(); readHex(); readHex(); readHex(); int codePoint = Integer.parseInt(s.substring(tempPos, tempPos + 4), 16); buf.append((char) codePoint); start = pos; continue; case 'n': special = '\n'; break; case 'r': special = '\r'; break; case 't': special = '\t'; break; case 'b': special = '\b'; break; case '"': special = '\"'; break; case '\\': special = '\\'; break; default: break; } //CHECKSTYLE:ON buf.append(s.substring(start, pos - 1)); if (special != 0) { pos++; buf.append(special); } start = pos; continue; } pos++; } buf.append(s.substring(start, pos)); if (quot > 0) { read(quot); } return buf.toString(); } /** * Parses a number. * * @return the next number (int or double). * @throws JSONParseException if invalid JSON is found */ public Number parseNumber() { get(); int start = this.pos; boolean isDouble = false; if (check('-') || check('+')) { pos++; } outer: while (pos < s.length()) { switch (s.charAt(pos)) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': pos++; break; case '.': isDouble = true; parseFraction(); break; case 'e': case 'E': isDouble = true; parseExponent(); break; default: break outer; } } try { if (isDouble) { return Double.valueOf(s.substring(start, pos)); } Long val = Long.valueOf(s.substring(start, pos)); if (val <= Integer.MAX_VALUE && val >= Integer.MIN_VALUE) { return val.intValue(); } return val; } catch (NumberFormatException e) { throw new JSONParseException(s, start, e); } } /** * Advances the pointed through <i>.digits</i>. */ public void parseFraction() { // get past . pos++; outer: while (pos < s.length()) { switch (s.charAt(pos)) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': pos++; break; case 'e': case 'E': parseExponent(); break; default: break outer; } } } /** * Advances the pointer through the exponent. */ public void parseExponent() { // get past E pos++; if (check('-') || check('+')) { pos++; } outer: while (pos < s.length()) { switch (s.charAt(pos)) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': pos++; break; default: break outer; } } } /** * Parses the next array. * * @return the array * @throws JSONParseException if invalid JSON is found */ public Object parseArray() { return parseArray(null); } /** * Parses the next array. * * @return the array * @throws JSONParseException if invalid JSON is found */ protected Object parseArray(final String name) { if (name != null) { _callback.arrayStart(name); } else { _callback.arrayStart(); } read('['); int i = 0; char current = get(); while (current != ']') { String elemName = String.valueOf(i++); Object elem = parse(elemName); doCallback(elemName, elem); if ((current = get()) == ',') { read(','); } else if (current == ']') { break; } else { throw new JSONParseException(s, pos); } } read(']'); return _callback.arrayDone(); } }