JsonTokenizer.java
/*
* Copyright 2015 Red Hat, Inc. and/or its affiliates.
*
* 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 org.dashbuilder.json;
/**
* Implementation of parsing a JSON string into instances of {@link
* org.dashbuilder.json.JsonValue}.
*/
class JsonTokenizer {
private static final int INVALID_CHAR = -1;
private static final String STOPCHARS = ",:]}/\\\"[{;=#";
private JsonFactory jsonFactory;
private boolean lenient = true;
private int pushBackBuffer = INVALID_CHAR;
private final String json;
private int position = 0;
JsonTokenizer(JsonFactory serverJsonFactory, String json) {
this.jsonFactory = serverJsonFactory;
this.json = json;
}
void back(char c) {
assert pushBackBuffer == INVALID_CHAR;
pushBackBuffer = c;
}
void back(int c) {
back((char) c);
}
int next() {
if (pushBackBuffer != INVALID_CHAR) {
final int c = pushBackBuffer;
pushBackBuffer = INVALID_CHAR;
return c;
}
return position < json.length() ? json.charAt(position++) : INVALID_CHAR;
}
String next(int n) throws JsonException {
if (n == 0) {
return "";
}
char[] buffer = new char[n];
int pos = 0;
if (pushBackBuffer != INVALID_CHAR) {
buffer[0] = (char) pushBackBuffer;
pos = 1;
pushBackBuffer = INVALID_CHAR;
}
int len;
while ((pos < n) && ((len = read(buffer, pos, n - pos)) != -1)) {
pos += len;
}
if (pos < n) {
throw new JsonException("Position " + pos + " less than " + n);
}
return String.valueOf(buffer);
}
int nextNonWhitespace() {
while (true) {
final int c = next();
if (!Character.isWhitespace((char) c)) {
return c;
}
}
}
String nextString(int startChar) throws JsonException {
final StringBuilder buffer = new StringBuilder();
int c = next();
assert c == '"' || (lenient && c == '\'');
while (true) {
c = next();
switch (c) {
case '\r':
case '\n':
throw new JsonException("");
case '\\':
c = next();
switch (c) {
case 'b':
buffer.append('\b');
break;
case 't':
buffer.append('\t');
break;
case 'n':
buffer.append('\n');
break;
case 'f':
buffer.append('\f');
break;
case 'r':
buffer.append('\r');
break;
// TODO: Not sure should even support this escaping
// mode since JSON is always UTF-8.
case 'u':
buffer.append((char) Integer.parseInt(next(4), 16));
break;
default:
buffer.append((char) c);
}
break;
default:
if (c == startChar) {
return buffer.toString();
}
buffer.append((char) c);
}
}
}
String nextUntilOneOf(String chars) {
final StringBuilder buffer = new StringBuilder();
int c = next();
while (c != INVALID_CHAR) {
if (Character.isWhitespace((char) c) || chars.indexOf((char) c) >= 0) {
back(c);
break;
}
buffer.append((char) c);
c = next();
}
return buffer.toString();
}
<T extends JsonValue> T nextValue() throws JsonException {
final int c = nextNonWhitespace();
back(c);
switch (c) {
case '"':
case '\'':
return (T) jsonFactory.create(nextString(c));
case '{':
return (T) parseObject();
case '[':
return (T) parseArray();
default:
return (T) getValueForLiteral(nextUntilOneOf(STOPCHARS));
}
}
JsonArray parseArray() throws JsonException {
final JsonArray array = jsonFactory.createArray();
int c = nextNonWhitespace();
assert c == '[';
while (true) {
c = nextNonWhitespace();
switch (c) {
case ']':
return array;
default:
back(c);
array.set(array.length(), (JsonValue) nextValue());
final int d = nextNonWhitespace();
switch (d) {
case ']':
return array;
case ',':
break;
default:
throw new JsonException("Invalid array: expected , or ]");
}
}
}
}
JsonObject parseObject() throws JsonException {
final JsonObject object = jsonFactory.createObject();
int c = nextNonWhitespace();
if (c != '{') {
throw new JsonException(
"Payload does not begin with '{'. Got " + c + "("
+ Character.valueOf((char) c) + ")");
}
while (true) {
c = nextNonWhitespace();
switch (c) {
case '}':
// We're done.
return object;
case '"':
case '\'':
back(c);
// Ready to start a key.
final String key = nextString(c);
if (nextNonWhitespace() != ':') {
throw new JsonException(
"Invalid object: expecting \":\"");
}
// TODO: Make sure this key is not already set.
object.put(key, (JsonValue) nextValue());
switch (nextNonWhitespace()) {
case ',':
break;
case '}':
return object;
default:
throw new JsonException(
"Invalid object: expecting } or ,");
}
break;
case ',':
break;
default:
if (lenient && (Character.isDigit((char) c) || Character.isLetterOrDigit((char) c))) {
StringBuilder keyBuffer = new StringBuilder();
keyBuffer.append(c);
while (true) {
c = next();
if (Character.isDigit((char) c) || Character.isLetterOrDigit((char) c)) {
keyBuffer.append(c);
} else {
back(c);
break;
}
}
if (nextNonWhitespace() != ':') {
throw new JsonException(
"Invalid object: expecting \":\"");
}
// TODO: Make sure this key is not already set.
object.put(keyBuffer.toString(), (JsonValue) nextValue());
switch (nextNonWhitespace()) {
case ',':
break;
case '}':
return object;
default:
throw new JsonException(
"Invalid object: expecting } or ,");
}
} else {
throw new JsonException("Invalid object: ");
}
}
}
}
private JsonNumber getNumberForLiteral(String literal)
throws JsonException {
try {
return jsonFactory.create(Double.parseDouble(literal));
} catch (NumberFormatException e) {
throw new JsonException("Invalid number literal: " + literal);
}
}
private JsonValue getValueForLiteral(String literal) throws JsonException {
if ("".equals(literal)) {
throw new JsonException("Missing value");
}
if ("null".equals(literal) || "undefined".equals(literal)) {
return jsonFactory.createNull();
}
if ("true".equals(literal)) {
return jsonFactory.create(true);
}
if ("false".equals(literal)) {
return jsonFactory.create(false);
}
final char c = literal.charAt(0);
if (c == '-' || Character.isDigit(c)) {
return getNumberForLiteral(literal);
}
throw new JsonException("Invalid literal: \"" + literal + "\"");
}
private int read(char[] buffer, int pos, int len) {
int maxLen = Math.min(json.length() - position, len);
String src = json.substring(position, position + maxLen);
char result[] = src.toCharArray();
System.arraycopy(result, 0, buffer, pos, maxLen);
position += maxLen;
return maxLen;
}
}