/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.felix.utils.json;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* A very small JSON parser.
*
* The JSON input is parsed into an object structure in the following way:
* <ul>
* <li>Object names are represented as a {@link String}.
* <li>String values are represented as a {@link String}.
* <li>Numeric values without a decimal separator are represented as a {@link Long}.
* <li>Numeric values with a decimal separator are represented as a {@link Double}.
* <li>Boolean values are represented as a {@link Boolean}.
* <li>Nested JSON objects are parsed into a {@link java.util.Map Map<String, Object>}.
* <li>JSON lists are parsed into a {@link java.util.List} which may contain any of the above values.
* </ul>
*/
public class JSONParser {
private static final Pattern KEY_VALUE_PATTERN = Pattern.compile("^\\s*[\"](.+?)[\"]\\s*[:]\\s*(.+)$");
private enum Scope { QUOTE, CURLY, BRACKET;
static Scope getScope(char c) {
switch (c) {
case '"':
return QUOTE;
case '[':
case ']':
return BRACKET;
case '{':
case '}':
return CURLY;
default:
return null;
}
}
}
static class Pair<K, V> {
final K key;
final V value;
Pair(K k, V v) {
key = k;
value = v;
}
}
private final Map<String, Object> parsed;
public JSONParser(CharSequence json) {
String str = json.toString();
str = str.trim().replace('\n', ' ').replace('\r', ' ');
parsed = parseObject(str);
}
public JSONParser(InputStream is) throws IOException {
this(readStreamAsString(is));
}
public Map<String, Object> getParsed() {
return parsed;
}
private static Pair<String, Object> parseKeyValue(String jsonKeyValue) {
Matcher matcher = KEY_VALUE_PATTERN.matcher(jsonKeyValue);
if (!matcher.matches() || matcher.groupCount() < 2) {
throw new IllegalArgumentException("Malformatted JSON key-value pair: " + jsonKeyValue);
}
return new Pair<String, Object>(unEscapeString(matcher.group(1)), parseValue(matcher.group(2)));
}
private static Object parseValue(String jsonValue) {
jsonValue = jsonValue.trim();
switch (jsonValue.charAt(0)) {
case '\"':
if (!jsonValue.endsWith("\""))
throw new IllegalArgumentException("Malformatted JSON string: " + jsonValue);
return unEscapeString(jsonValue.substring(1, jsonValue.length() - 1));
case '[':
List<Object> entries = new ArrayList<Object>();
for (String v : parseListValuesRaw(jsonValue)) {
entries.add(parseValue(v));
}
return entries;
case '{':
return parseObject(jsonValue);
case 't':
case 'T':
case 'f':
case 'F':
return Boolean.parseBoolean(jsonValue);
case 'n':
case 'N':
return null;
default:
if (jsonValue.contains(".")) {
return Double.parseDouble(jsonValue);
}
return Long.parseLong(jsonValue);
}
}
private static String unEscapeString(String s) {
StringBuilder sb = new StringBuilder(s);
for (int i = 0; i<sb.length(); i++) {
if (sb.charAt(i) == '\\' && sb.length() > i+1) {
sb.deleteCharAt(i);
char nextChar = sb.charAt(i);
switch (nextChar) {
case 'b':
sb.setCharAt(i, '\b');
break;
case 'f':
sb.setCharAt(i, '\f');
break;
case 'n':
sb.setCharAt(i, '\n');
break;
case 'r':
sb.setCharAt(i, '\r');
break;
case 't':
sb.setCharAt(i, '\t');
break;
case 'u':
if (sb.length() > i+4) {
int uc = Integer.parseInt(sb.substring(i+1, i+5), 16);
sb.replace(i, i+5, "" + (char) uc);
}
break;
}
}
}
return sb.toString();
}
private static Map<String, Object> parseObject(String jsonObject) {
if (!(jsonObject.startsWith("{") && jsonObject.endsWith("}")))
throw new IllegalArgumentException("Malformatted JSON object: " + jsonObject);
Map<String, Object> values = new HashMap<String, Object>();
jsonObject = jsonObject.substring(1, jsonObject.length() - 1).trim();
if (jsonObject.length() == 0)
return values;
for (String element : parseKeyValueListRaw(jsonObject)) {
Pair<String, Object> pair = parseKeyValue(element);
values.put(pair.key, pair.value);
}
return values;
}
private static List<String> parseKeyValueListRaw(String jsonKeyValueList) {
if (jsonKeyValueList.trim().length() == 0)
return Collections.emptyList();
jsonKeyValueList = jsonKeyValueList + ","; // append comma to simplify parsing
List<String> elements = new ArrayList<String>();
int i=0;
int start=0;
Stack<Scope> scopeStack = new Stack<Scope>();
while (i < jsonKeyValueList.length()) {
char curChar = jsonKeyValueList.charAt(i);
switch (curChar) {
case '"':
if (i > 0 && jsonKeyValueList.charAt(i-1) == '\\') {
// it's escaped, ignore for now
} else {
if (!scopeStack.empty() && scopeStack.peek() == Scope.QUOTE) {
scopeStack.pop();
} else {
scopeStack.push(Scope.QUOTE);
}
}
break;
case '[':
case '{':
if ((scopeStack.empty() ? null : scopeStack.peek()) == Scope.QUOTE) {
// inside quotes, ignore
} else {
scopeStack.push(Scope.getScope(curChar));
}
break;
case ']':
case '}':
Scope curScope = scopeStack.empty() ? null : scopeStack.peek();
if (curScope == Scope.QUOTE) {
// inside quotes, ignore
} else {
Scope newScope = Scope.getScope(curChar);
if (curScope == newScope) {
scopeStack.pop();
} else {
throw new IllegalArgumentException("Unbalanced closing " +
curChar + " in: " + jsonKeyValueList);
}
}
break;
case ',':
if (scopeStack.empty()) {
elements.add(jsonKeyValueList.substring(start, i));
start = i+1;
}
break;
}
i++;
}
return elements;
}
private static List<String> parseListValuesRaw(String jsonList) {
if (!(jsonList.startsWith("[") && jsonList.endsWith("]")))
throw new IllegalArgumentException("Malformatted JSON list: " + jsonList);
jsonList = jsonList.substring(1, jsonList.length() - 1);
return parseKeyValueListRaw(jsonList);
}
/**
* Read an entire input stream into a byte array.
* @param is The input stream to read.
* @return The byte array with the contents of the input stream.
* @throws IOException if the underlying read operation on the input stream
* throws an error.
*/
private static byte [] readStream(InputStream is) throws IOException {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] bytes = new byte[65536];
int length = 0;
int offset = 0;
while ((length = is.read(bytes, offset, bytes.length - offset)) != -1) {
offset += length;
if (offset == bytes.length) {
baos.write(bytes, 0, bytes.length);
offset = 0;
}
}
if (offset != 0) {
baos.write(bytes, 0, offset);
}
return baos.toByteArray();
} finally {
is.close();
}
}
private static String readStreamAsString(InputStream is) throws IOException {
byte [] bytes = readStream(is);
if (bytes.length < 5)
// need at least 5 bytes to establish the encoding
throw new IllegalArgumentException("Malformatted JSON");
int offset = 0;
if ((bytes[0] == -1 && bytes[1] == -2)
|| (bytes[0] == -2 && bytes[1] == -1)) {
// Skip UTF16/UTF32 Byte Order Mark (BOM)
offset = 2;
}
/* Infer the encoding as described in section 3 of http://www.ietf.org/rfc/rfc4627.txt
* which reads:
* Encoding
*
* JSON text SHALL be encoded in Unicode. The default encoding is
* UTF-8.
*
* Since the first two characters of a JSON text will always be ASCII
* characters [RFC0020], it is possible to determine whether an octet
* stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
* at the pattern of nulls in the first four octets.
*
* 00 00 00 xx UTF-32BE
* 00 xx 00 xx UTF-16BE
* xx 00 00 00 UTF-32LE
* xx 00 xx 00 UTF-16LE
* xx xx xx xx UTF-8
*/
String encoding;
if (bytes[offset + 2] == 0) {
if (bytes[offset + 1] != 0) {
encoding = "UTF-16";
} else {
encoding = "UTF-32";
}
} else if (bytes[offset + 1] == 0) {
encoding = "UTF-16";
} else {
encoding = "UTF-8";
}
return new String(bytes, encoding);
}
}