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BasicJsonParser.java
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BasicJsonParser.java
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/*
* Copyright 2012-2022 the original author or authors.
*
* 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
*
* https://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.springframework.boot.json;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;
/**
* Really basic JSON parser for when you have nothing else available. Comes with some
* limitations with respect to the JSON specification (e.g. only supports String values),
* so users will probably prefer to have a library handle things instead (Jackson or Snake
* YAML are supported).
*
* @author Dave Syer
* @author Jean de Klerk
* @author Stephane Nicoll
* @since 1.2.0
* @see JsonParserFactory
*/
public class BasicJsonParser extends AbstractJsonParser {
private static final int MAX_DEPTH = 1000;
@Override
public Map<String, Object> parseMap(String json) {
return tryParse(() -> parseMap(json, this::parseMapInternal), Exception.class);
}
@Override
public List<Object> parseList(String json) {
return tryParse(() -> parseList(json, (jsonToParse) -> parseListInternal(0, jsonToParse)), Exception.class);
}
private List<Object> parseListInternal(int nesting, String json) {
List<Object> list = new ArrayList<>();
json = trimLeadingCharacter(trimTrailingCharacter(json, ']'), '[').trim();
for (String value : tokenize(json)) {
list.add(parseInternal(nesting + 1, value));
}
return list;
}
private Object parseInternal(int nesting, String json) {
if (nesting > MAX_DEPTH) {
throw new IllegalStateException("JSON is too deeply nested");
}
if (json.startsWith("[")) {
return parseListInternal(nesting + 1, json);
}
if (json.startsWith("{")) {
return parseMapInternal(json);
}
if (json.startsWith("\"")) {
return trimTrailingCharacter(trimLeadingCharacter(json, '"'), '"');
}
try {
return Long.valueOf(json);
}
catch (NumberFormatException ex) {
// ignore
}
try {
return Double.valueOf(json);
}
catch (NumberFormatException ex) {
// ignore
}
return json;
}
private Map<String, Object> parseMapInternal(String json) {
Map<String, Object> map = new LinkedHashMap<>();
json = trimLeadingCharacter(trimTrailingCharacter(json, '}'), '{').trim();
for (String pair : tokenize(json)) {
String[] values = StringUtils.trimArrayElements(StringUtils.split(pair, ":"));
Assert.state(values[0].startsWith("\"") && values[0].endsWith("\""),
"Expecting double-quotes around field names");
String key = trimLeadingCharacter(trimTrailingCharacter(values[0], '"'), '"');
Object value = parseInternal(0, values[1]);
map.put(key, value);
}
return map;
}
private static String trimTrailingCharacter(String string, char c) {
if (!string.isEmpty() && string.charAt(string.length() - 1) == c) {
return string.substring(0, string.length() - 1);
}
return string;
}
private static String trimLeadingCharacter(String string, char c) {
if (!string.isEmpty() && string.charAt(0) == c) {
return string.substring(1);
}
return string;
}
private List<String> tokenize(String json) {
List<String> list = new ArrayList<>();
int index = 0;
int inObject = 0;
int inList = 0;
boolean inValue = false;
boolean inEscape = false;
StringBuilder build = new StringBuilder();
while (index < json.length()) {
char current = json.charAt(index);
if (inEscape) {
build.append(current);
index++;
inEscape = false;
continue;
}
if (current == '{') {
inObject++;
}
if (current == '}') {
inObject--;
}
if (current == '[') {
inList++;
}
if (current == ']') {
inList--;
}
if (current == '"') {
inValue = !inValue;
}
if (current == ',' && inObject == 0 && inList == 0 && !inValue) {
list.add(build.toString());
build.setLength(0);
}
else if (current == '\\') {
inEscape = true;
}
else {
build.append(current);
}
index++;
}
if (build.length() > 0) {
list.add(build.toString().trim());
}
return list;
}
}