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javajs.util.JSJSONParser Maven / Gradle / Ivy
Jmol: an open-source Java viewer for chemical structures in 3D
package javajs.util;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import javajs.J2SIgnoreImport;
/**
* a very simple JSON parser for JSON objects that are compatible with JavaScript
* A gross simplification of https://github.com/douglascrockford/JSON-java
*
* A SUBSET of JSON with similarly to window.JSON.parse():
*
* In JavaScript returns "null" for a null value, not null
*
* -- requires quoted strings for keys and values
*
* -- does not allow /xxx/ objects
*
* @author Bob Hanson
*
*/
@J2SIgnoreImport({ HashMap.class })
public class JSJSONParser {
private String str;
private int index;
private int len;
private boolean asHashTable;
public JSJSONParser () {
// for reflection
}
/**
* requires { "key":"value", "key":"value",....}
*
* @param str
* @param asHashTable TODO
*
* @return Map or null
*/
@SuppressWarnings("unchecked")
public Map parseMap(String str, boolean asHashTable) {
index = 0;
this.asHashTable = asHashTable;
this.str = str;
len = str.length();
if (getChar() != '{')
return null;
returnChar();
return (Map) getValue(false);
}
/**
* Could return Integer, Float, Boolean, String, Map, Lst, or null
*
* @param str
* @return a object equivalent to the JSON string str
*
*/
public Object parse(String str) {
index = 0;
this.str = str;
len = str.length();
return getValue(false);
}
private char next() {
return (index < len ? str.charAt(index++) : '\0');
}
private void returnChar() {
index--;
}
/**
* Get the next char in the string, skipping whitespace.
*
* @throws JSONException
* @return one character, or 0 if there are no more characters.
*/
private char getChar() throws JSONException {
for (;;) {
char c = next();
if (c == 0 || c > ' ') {
return c;
}
}
}
/**
* only allowing the following values:
*
* {...} object
*
* [...] array
*
* Integer
*
* Float
*
* "quoted string"
*
*
* @param isKey if we should allow {...} and [...]
* @return a subclass of Object
* @throws JSONException
*/
private Object getValue(boolean isKey) throws JSONException {
int i = index;
char c = getChar();
switch (c) {
case '\0':
return null;
case '"':
case '\'':
return getString(c);
case '{':
if (!isKey)
return getObject();
c = 0;
break;
case '[':
if (!isKey)
return getArray();
c = 0;
break;
default:
// standard syntax is assumed; not checking all possible invalid keys
// for example, "-" is not allowed in JavaScript, which is what this is for
returnChar();
while (c >= ' ' && "[,]{:}'\"".indexOf(c) < 0)
c = next();
returnChar();
if (isKey && c != ':')
c = 0;
break;
}
if (isKey && c == 0)
throw new JSONException("invalid key");
String string = str.substring(i, index);
// check for the only valid simple words: true, false, null (lower case)
// and in this case, only for
if (!isKey) {
if (string.equals("true")) {
return Boolean.TRUE;
}
if (string.equals("false")) {
return Boolean.FALSE;
}
if (string.equals("null")) {
return (asHashTable ? string : null);
}
}
// only numbers from here on:
c = string.charAt(0);
if (c >= '0' && c <= '9' || c == '-')
try {
if (string.indexOf('.') < 0 && string.indexOf('e') < 0
&& string.indexOf('E') < 0)
return new Integer(string);
// not allowing infinity or NaN
// using float here because Jmol does not use Double
Float d = Float.valueOf(string);
if (!d.isInfinite() && !d.isNaN())
return d;
} catch (Exception e) {
}
// not a valid number
System.out.println("JSON parser cannot parse " + string);
throw new JSONException("invalid value");
}
private String getString(char quote) throws JSONException {
char c;
SB sb = null;
int i0 = index;
for (;;) {
int i1 = index;
switch (c = next()) {
case '\0':
case '\n':
case '\r':
throw syntaxError("Unterminated string");
case '\\':
switch (c = next()) {
case '"':
case '\'':
case '\\':
case '/':
break;
case 'b':
c = '\b';
break;
case 't':
c = '\t';
break;
case 'n':
c = '\n';
break;
case 'f':
c = '\f';
break;
case 'r':
c = '\r';
break;
case 'u':
int i = index;
index += 4;
try {
c = (char) Integer.parseInt(str.substring(i, index), 16);
} catch (Exception e) {
throw syntaxError("Substring bounds error");
}
break;
default:
throw syntaxError("Illegal escape.");
}
break;
default:
if (c == quote)
return (sb == null ? str.substring(i0, i1) : sb.toString());
break;
}
if (index > i1 + 1) {
if (sb == null) {
sb = new SB();
sb.append(str.substring(i0, i1));
}
}
if (sb != null)
sb.appendC(c);
}
}
private Object getObject() {
Map map = (asHashTable ? new Hashtable() : new HashMap());
String key = null;
switch (getChar()) {
case '}':
return map;
case 0:
throw new JSONException("invalid object");
}
returnChar();
boolean isKey = false;
for (;;) {
if ((isKey = !isKey) == true)
key = getValue(true).toString();
else
map.put(key, getValue(false));
switch (getChar()) {
case '}':
return map;
case ':':
if (isKey)
continue;
isKey = true;
//$FALL-THROUGH$
case ',':
if (!isKey)
continue;
//$FALL-THROUGH$
default:
throw syntaxError("Expected ',' or ':' or '}'");
}
}
}
private Object getArray() {
Lst l = new Lst();
switch (getChar()) {
case ']':
return l;
case 0:
throw new JSONException("invalid array");
}
returnChar();
boolean isNull = false;
for (;;) {
if (isNull) {
l.addLast(null);
isNull = false;
} else {
l.addLast(getValue(false));
}
switch (getChar()) {
case ',':
switch (getChar()) {
case ']':
// terminal ,
return l;
case ',':
// empty value
isNull = true;
//$FALL-THROUGH$
default:
returnChar();
}
continue;
case ']':
return l;
default:
throw syntaxError("Expected ',' or ']'");
}
}
}
/**
* Make a JSONException to signal a syntax error.
*
* @param message
* The error message.
* @return A JSONException object, suitable for throwing
*/
public JSONException syntaxError(String message) {
return new JSONException(message + " for " + str.substring(0, Math.min(index, len)));
}
}
