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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 {
private JsonParse() {}
/**
* Converts jsonString into a {@link Map}
* @param jsonString parsed
* @return the contents of the jsonString
*/
public static Map map(String jsonString) {
return (Map) parse(jsonString);
}
/**
* Converts jsonString into a {@link List}
* @param jsonString parsed
* @return the contents of the jsonString
*/
public static List list(String jsonString) {
return (List) parse(jsonString);
}
/**
* Pulls the internal JSON string from jsonString and returns it
* @param jsonString parsed
* @return the contents of the jsonString
*/
public static String string(String jsonString) {
return (String) parse(jsonString);
}
/**
* Converts jsonString into a {@link Number}, be it an integer or floating-point
* @param jsonString parsed
* @return the contents of the jsonString
*/
public static Number number(String jsonString) {
return (Number) parse(jsonString);
}
/**
* Converts jsonString into a boolean
* @param jsonString parsed
* @return the contents of the jsonString
*/
public static boolean bool(String jsonString) {
return (boolean) parse(jsonString);
}
/**
* Parses jsonString according to what the outermost structure is
* @param jsonString parsed
* @return the contents of jsonString
*/
@SuppressWarnings("ConstantConditions")
public static Object parse(String jsonString) {
Stack stateStack = new Stack<>();
Type currentType;
boolean expectingComma = false, expectingColon = false;
int fieldStart = 0, end = jsonString.length() - 1, i = 0;
String propertyName = null;
Object currentContainer = null;
Object value;
char current;
while (Constants.isWhitespace((current = jsonString.charAt(i)))) {
if (i >= end) {
throw new JsonParseException("Provided string did not contain a value");
}
i++;
}
if (current == '{') {
currentType = Type.OBJECT;
currentContainer = new HashMap<>();
i++;
} else if (current == '[') {
currentType = Type.ARRAY;
currentContainer = new ArrayList<>();
propertyName = null;
i++;
} else if (current == '"') {
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)
currentType = Type.CONSTANT;
fieldStart = i;
} else if (Constants.isNumberStart(current)) {
currentType = Type.NUMBER;
fieldStart = i;
} else {
throw new JsonParseException(stateStack, "Unexpected character \"" + current + "\" instead of root value");
}
while (i <= end) {
current = jsonString.charAt(i);
switch (currentType) {
case 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);
currentType = Type.HEURISTIC;
expectingColon = true;
i++;
break;
case STRING:
// Fast-forward to end of string value, which is a '"' character
do {
i = jsonString.indexOf('"', i + 1);
} while (jsonString.charAt(i - 1) == '\\');
value = jsonString.substring(fieldStart, i);
if (currentContainer == null) {
return value;
} else {
expectingComma = true;
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
currentType = Type.OBJECT;
} else {
((List) currentContainer).add(value);
currentType = Type.ARRAY;
}
}
i++;
break;
case NUMBER: {
boolean withDecimal = false;
while (Constants.isNumber(current) && i++ < end) {
if (!withDecimal && current == '.' || current == 'e' || current == 'E') {
withDecimal = true;
}
current = jsonString.charAt(i);
}
String valueString = jsonString.substring(fieldStart, i);
try {
if (withDecimal) {
value = Double.valueOf(valueString);
} else {
value = Long.valueOf(valueString);
}
} catch (NumberFormatException e) {
throw new JsonParseException(stateStack, "\"" + valueString +
"\" expected to be a number, but wasn't");
}
if (currentContainer == null) {
return value;
} else {
expectingComma = true;
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
currentType = Type.OBJECT;
} else {
((List) currentContainer).add(value);
currentType = Type.ARRAY;
}
}
break;
}
case CONSTANT:
while (Constants.isLetter(current) && i++ < end) {
current = jsonString.charAt(i);
}
String valueString = jsonString.substring(fieldStart, i);
switch (valueString) {
case "false":
value = false;
break;
case "true":
value = true;
break;
case "null":
value = null;
break;
default:
if (currentContainer instanceof Map) {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
} else if (currentContainer instanceof List) {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
}
throw new JsonParseException(stateStack, "\"" + valueString
+ "\" is not a valid constant. Missing quotes?");
}
if (currentContainer == null) {
return value;
} else {
expectingComma = true;
if (currentContainer instanceof Map) {
((Map) currentContainer).put(propertyName, value);
currentType = Type.OBJECT;
} else {
((List) currentContainer).add(value);
currentType = Type.ARRAY;
}
}
break;
case HEURISTIC:
while (Constants.isWhitespace(current) && i++ < end) {
current = jsonString.charAt(i);
}
if (current != ':' && expectingColon) {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
throw new JsonParseException(stateStack, "wasn't followed by a colon");
}
if (current == ':') {
if (expectingColon) {
expectingColon = false;
i++;
} else {
throw new JsonParseException(stateStack, "wasn't followed by too many colons");
}
} else if (current == '"') {
currentType = Type.STRING;
fieldStart = i + 1; // Don't start with current `i`, as it is delimiter: '"'
} else if (current == '{') {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
currentType = Type.OBJECT;
currentContainer = new HashMap<>();
i++;
} else if (current == '[') {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
currentType = Type.ARRAY;
currentContainer = new ArrayList<>();
propertyName = null;
i++;
} else if (Constants.isLetter(current)) {
// Assume parsing a constant ("null", "true", "false", etc)
currentType = Type.CONSTANT;
fieldStart = i;
} else if (Constants.isNumberStart(current)) {
// Is a number
currentType = Type.NUMBER;
fieldStart = i;
} else {
throw new JsonParseException(stateStack, "unexpected character \"" + current +
"\" instead of object value");
}
break;
case OBJECT:
while (Constants.isWhitespace(current) && i++ < end) {
current = jsonString.charAt(i);
}
if (current == ',') {
if (expectingComma) {
expectingComma = false;
i++;
} else {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
throw new JsonParseException(stateStack, "followed by too many commas");
}
} else if (current == '"') {
if (expectingComma) {
stateStack.push(new State(propertyName, currentContainer, Type.OBJECT));
throw new JsonParseException(stateStack, "wasn't followed by a comma");
}
currentType = Type.NAME;
fieldStart = i + 1; // Don't start with `current`, as it is the beginning quotation
} else if (current == '}') {
if (!stateStack.isEmpty()) {
State upper = stateStack.pop();
Object upperContainer = upper.container;
String parentName = upper.propertyName;
currentType = upper.type;
if (upperContainer instanceof Map) {
((Map) upperContainer).put(parentName, currentContainer);
} else {
((List) upperContainer).add(currentContainer);
}
currentContainer = upperContainer;
expectingComma = true;
i++;
} else {
return currentContainer;
}
} else if (!Constants.isWhitespace(current)) {
throw new JsonParseException(stateStack, "unexpected character '" + current +
"' where a property name is expected. Missing quotes?");
}
break;
case ARRAY:
while (Constants.isWhitespace(current) && i++ < end) {
current = jsonString.charAt(i);
}
if (current != ',' && current != ']' && current != '}' && expectingComma) {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
throw new JsonParseException(stateStack, "wasn't preceded by a comma");
}
if (current == ',') {
if (expectingComma) {
expectingComma = false;
i++;
} else {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
throw new JsonParseException(stateStack, "preceded by too many commas");
}
} else if (current == '"') {
currentType = Type.STRING;
fieldStart = i + 1; // Don't start with current `i`, as it is delimiter: '"'
} else if (current == '{') {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
currentType = Type.OBJECT;
currentContainer = new HashMap<>();
i++;
} else if (current == '[') {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
currentType = Type.ARRAY;
currentContainer = new ArrayList<>();
i++;
} else if (current == ']') {
if (!stateStack.isEmpty()) {
State upper = stateStack.pop();
Object upperContainer = upper.container;
String parentName = upper.propertyName;
currentType = upper.type;
if (upperContainer instanceof Map) {
((Map) upperContainer).put(parentName, currentContainer);
} else {
((List) upperContainer).add(currentContainer);
}
currentContainer = upperContainer;
expectingComma = true;
i++;
} else {
return currentContainer;
}
} else if (Constants.isLetter(current)) {
// Assume parsing a constant ("null", "true", "false", etc)
currentType = Type.CONSTANT;
fieldStart = i;
} else if (Constants.isNumberStart(current)) {
// Is a number
currentType = Type.NUMBER;
fieldStart = i;
} else {
stateStack.push(new State(propertyName, currentContainer, Type.ARRAY));
throw new JsonParseException("Unexpected character \"" + current + "\" instead of array value");
}
break;
}
}
throw new JsonParseException("Root element wasn't terminated correctly (Missing ']' or '}'?)");
}
enum Type {
ARRAY,
OBJECT,
HEURISTIC,
NAME,
STRING,
NUMBER,
CONSTANT
}
static class State {
final String propertyName;
final Object container;
final Type type;
State(String propertyName, Object container, Type type) {
this.propertyName = propertyName;
this.container = container;
this.type = type;
}
}
}
