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ca.fuzzlesoft.JsonParse Maven / Gradle / Ivy
package ca.fuzzlesoft;
import java.util.*;
/**
* Parses JSON, converting it into {@link List}s and {@link Map}s. Is thread safe.
*
* @author mitch
* @since 30/12/15
*/
@SuppressWarnings("unchecked") //Because of reusing `currentContainer` for both maps and lists
public class JsonParse {
/**
* Converts jsonString into a {@link Map}
* @param jsonString parsed
* @return the contents of the jsonString
*/
public Map map(String jsonString) {
return (Map) parse(jsonString, Type.OBJECT);
}
/**
* Converts jsonString into a {@link List}
* @param jsonString parsed
* @return the contents of the jsonString
*/
public List list(String jsonString) {
return (List) parse(jsonString, Type.ARRAY);
}
/**
* Parses jsonString according to what the outermost structure is
* @param jsonString parsed
* @param type type of outermost structure, expecting {@link Type#OBJECT} or {@link Type#ARRAY}
* @return the contents of jsonString
*/
@SuppressWarnings("ConstantConditions")
public static Object parse(String jsonString, Type type) {
Stack propertyNameStack = new Stack<>();
Stack containerStack = new Stack<>();
Stack typeStack = new Stack<>();
typeStack.push(type);
Type currentType = type;
boolean expectingComma = false, expectingColon = false;
int fieldStart = 0, offset, endOffset;
String propertyName;
Object currentContainer;
if (type == Type.OBJECT) {
offset = jsonString.indexOf('{');
endOffset = jsonString.lastIndexOf('}');
currentContainer = new HashMap<>();
propertyName = ""; // Will be set whenever property name is entered
} else if (type == Type.ARRAY) {
offset = jsonString.indexOf('[');
endOffset = jsonString.lastIndexOf(']');
currentContainer = new ArrayList<>();
propertyName = "[]";
} else {
throw new JsonParseException("Can't parse a structure that isn't an OBJECT or ARRAY");
}
if (offset == -1 || endOffset == -1) {
throw new JsonParseException("Json string didn't contain an " + type);
}
char current;
int i;
for (i = offset + 1; i <= endOffset; i++) {
current = jsonString.charAt(i);
// Have to check if in a value string/name first. If so, ignore any special
// characters (commas, colons, object literals, etc.)
if (currentType == Type.STRING) {
// Fast-forward to end of string value, which is a '"' character
do {
i = jsonString.indexOf('"', i + 1);
} while (jsonString.charAt(i - 1) == '\\');
Object value = jsonString.substring(fieldStart, i);
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
} else {
((List) currentContainer).add(value);
}
expectingComma = true;
typeStack.pop();
currentType = typeStack.peek();
continue;
}
if (currentType == Type.NAME) {
// Fast-forward to destination, which is an ending quote
do {
i = jsonString.indexOf('"', i + 1);
} while (jsonString.charAt(i - 1) == '\\');
propertyName = jsonString.substring(fieldStart, i);
typeStack.pop();
typeStack.push(Type.HEURISTIC);
currentType = Type.HEURISTIC;
expectingColon = true;
continue;
}
if (currentType == Type.NUMBER) {
boolean withDecimal = false;
while (current != ',' && current != '}' && current != ']' && !Constants.isWhitespace(current) && i < endOffset) {
if (!withDecimal && current == '.' || current == 'e' || current == 'E') {
withDecimal = true;
}
current = jsonString.charAt(++i);
}
String valueString = jsonString.substring(fieldStart, i);
Object value;
try {
if (withDecimal) {
value = Double.valueOf(valueString);
} else {
value = Long.valueOf(valueString);
}
} catch (NumberFormatException e) {
propertyNameStack.push(propertyName);
throw new JsonParseException(propertyNameStack, "\"" + valueString
+ "\" expected to be a number, but wasn't");
}
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
} else {
((List) currentContainer).add(value);
}
typeStack.pop();
currentType = typeStack.peek();
if (Constants.isWhitespace(current)) {
expectingComma = true;
continue;
}
if (current != ']' && current != '}') {
continue;
}
}
if (currentType == Type.CONSTANT) {
while (current != ',' && current != '}' && current != ']' && !Constants.isWhitespace(current) && i < endOffset) {
current = jsonString.charAt(++i);
}
String valueString = jsonString.substring(fieldStart, i);
Object value;
if (valueString.equals("false")) {
value = false;
} else if (valueString.equals("true")) {
value = true;
} else if (valueString.equals("null")) {
value = null;
} else {
propertyNameStack.push(propertyName);
throw new JsonParseException(propertyNameStack, "\"" + valueString
+ "\" is not a valid constant. Maybe missing quotes?");
}
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
} else {
((List) currentContainer).add(value);
}
typeStack.pop();
currentType = typeStack.peek();
if (Constants.isWhitespace(current)) {
expectingComma = true;
continue;
}
if (current != ']' && current != '}') {
continue;
}
}
// Check ending literals next, because they can act in place of commas or whitespace in terminating a value
if (current == '}' || current == ']') {
if (i == endOffset) {
continue;
}
if (containerStack.isEmpty()) throw new JsonParseException("Too many closing tags");
Object upperContainer = containerStack.pop();
String parentName = propertyNameStack.pop();
if (upperContainer instanceof Map) {
((Map) upperContainer).put(parentName, currentContainer);
} else {
((List) upperContainer).add(currentContainer);
}
currentContainer = upperContainer;
expectingComma = true;
typeStack.pop();
currentType = typeStack.peek();
continue;
}
if (expectingComma) {
if (current == ',') {
expectingComma = false;
} else if (!Constants.isWhitespace(current)) {
propertyNameStack.push(propertyName);
throw new JsonParseException(propertyNameStack, "wasn't followed by a comma");
}
continue;
}
if (expectingColon) {
if (current == ':') {
expectingColon = false;
} else if (!Constants.isWhitespace(current)) {
propertyNameStack.push(propertyName);
throw new JsonParseException(propertyNameStack, "\"" + propertyName + "\" wasn't followed by a colon");
}
continue;
}
if (currentType == Type.HEURISTIC) {
if (current == '"') {
typeStack.pop();
typeStack.push(Type.STRING);
currentType = Type.STRING;
fieldStart = i + 1; // Don't start with current `i`, as it is delimiter: '"'
} else if (Constants.isLetter(current)) {
// Assume parsing a constant ("null", "true", "false", etc)
typeStack.pop();
typeStack.push(Type.CONSTANT);
currentType = Type.CONSTANT;
fieldStart = i;
} else if (current == '{') {
typeStack.pop();
typeStack.push(Type.OBJECT);
currentType = Type.OBJECT;
propertyNameStack.push(propertyName);
containerStack.push(currentContainer);
currentContainer = new HashMap<>();
} else if (current == '[') {
typeStack.pop();
typeStack.push(Type.ARRAY);
currentType = Type.ARRAY;
propertyNameStack.push(propertyName);
containerStack.push(currentContainer);
currentContainer = new ArrayList<>();
propertyName = "[]";
} else if (!Constants.isWhitespace(current)) {
// Is a number
typeStack.pop();
typeStack.push(Type.NUMBER);
currentType = Type.NUMBER;
fieldStart = i;
}
continue;
}
if (currentType == Type.OBJECT) {
if (current == '"') {
typeStack.push(Type.NAME);
currentType = Type.NAME;
fieldStart = i + 1; // Don't start with `current`, as it is the beginning quotation
continue;
} else if (Constants.isWhitespace(current)) {
continue;
}
throw new JsonParseException(propertyNameStack,
"unexpected character '" + current + "' where a property name is expected");
}
if (currentType == Type.ARRAY) {
if (current == '"') {
typeStack.push(Type.STRING);
currentType = Type.STRING;
fieldStart = i + 1; // Don't start with current `i`, as it is delimiter: '"'
} else if (Constants.isLetter(current)){
// Assume parsing a constant ("null", "true", "false", etc)
typeStack.push(Type.CONSTANT);
currentType = Type.CONSTANT;
fieldStart = i;
} else if (current == '{') {
typeStack.push(Type.OBJECT);
currentType = Type.OBJECT;
propertyNameStack.push(propertyName);
containerStack.push(currentContainer);
currentContainer = new HashMap<>();
} else if (current == '[') {
typeStack.push(Type.ARRAY);
currentType = Type.ARRAY;
propertyNameStack.push(propertyName);
containerStack.push(currentContainer);
currentContainer = new ArrayList<>();
} else if (!Constants.isWhitespace(current)) {
// Is a number
typeStack.push(Type.NUMBER);
currentType = Type.NUMBER;
fieldStart = i;
}
}
}
return currentContainer;
}
enum Type {
NAME,
HEURISTIC,
NUMBER,
STRING,
CONSTANT,
OBJECT,
ARRAY
}
}
