com.blazebit.persistence.parser.JsonParser Maven / Gradle / Ivy
/*
* Copyright 2014 - 2021 Blazebit.
*
* 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.blazebit.persistence.parser;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* This is a specialized parser for the JSON structure that will be produced by the JSON functions in Blaze-Persistence.
* The parser can only parse valid JSON that conforms to that structure. Other JSON may run into problems.
*
* @author Christian Beikov
* @since 1.5.0
*/
public final class JsonParser {
private JsonParser() {
}
public static List parseStringOnly(CharSequence json, String... fields) {
List list = new ArrayList<>();
StringBuilder sb = new StringBuilder();
if (json != null && json.length() != 0) {
Map fieldMap = new HashMap<>(fields.length);
for (int i = 0; i < fields.length; i++) {
fieldMap.put(fields[i], i);
}
int start = CharSequenceUtils.indexOf(json, '[') + 1;
int end = CharSequenceUtils.lastIndexOf(json, ']');
for (int i = start; i < end; i++) {
Object[] object = new Object[fields.length];
boolean quoteMode = false;
int fieldIndex = -1;
boolean escapes = false;
i = CharSequenceUtils.indexOf(json, '{', i) + 1;
for (; i < end; i++) {
char c = json.charAt(i);
if (!quoteMode) {
if (c == '"') {
quoteMode = true;
} else if (c == '}') {
break;
} else if (c != ':' && c != ',' && !Character.isWhitespace(c)) {
// non-string value
switch (c) {
case 'n':
object[fieldIndex] = null;
i += 3;
fieldIndex = -1;
escapes = false;
break;
case '[':
// Nested object handling
int nestedEnd = findEnd(json, i);
object[fieldIndex] = new SubSequence(json, i, nestedEnd);
fieldIndex = -1;
i = nestedEnd - 1;
break;
default:
throw new IllegalArgumentException("Non-String value unsupported! Found at: " + i);
}
}
} else {
if (c == '\\') {
escapes = true;
c = json.charAt(++i);
switch (c) {
case 'b':
c = '\b';
break;
case 'f':
c = '\f';
break;
case 'r':
c = '\r';
break;
case 'n':
c = '\n';
break;
case 't':
c = '\t';
break;
case 'u':
c = (char) Integer.parseInt(json.subSequence(i + 1, i + 5).toString(), 16);
i += 4;
break;
case '"':
case '\\':
case '/':
break;
default:
throw new IllegalStateException("Unexpected escape sequence at position: " + i);
}
sb.append(c);
} else if (c == '"') {
if (fieldIndex == -1) {
fieldIndex = fieldMap.get(sb.toString());
} else {
if (escapes) {
object[fieldIndex] = sb.toString();
} else {
object[fieldIndex] = new SubSequence(json, i - sb.length(), i);
}
fieldIndex = -1;
escapes = false;
}
sb.setLength(0);
quoteMode = false;
} else {
sb.append(c);
}
}
}
list.add(object);
}
}
return list;
}
private static int findEnd(CharSequence json, int i) {
int arrayLevel = 1;
int end = json.length();
boolean quoteMode = false;
i++;
for (;i < end; i++) {
final char c = json.charAt(i);
if (!quoteMode) {
switch (c) {
case '"':
quoteMode = true;
break;
case '[':
arrayLevel++;
break;
case ']':
arrayLevel--;
if (arrayLevel == 0) {
return i + 1;
}
break;
default:
break;
}
} else if (c == '\\') {
i++;
} else if (c == '"') {
quoteMode = false;
}
}
return i;
}
}