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Groovy: A powerful, dynamic language for the JVM
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 groovy.json;
import groovy.io.LineColumnReader;
import java.io.IOException;
import java.io.Reader;
import java.util.Iterator;
import static groovy.json.JsonTokenType.FALSE;
import static groovy.json.JsonTokenType.NUMBER;
import static groovy.json.JsonTokenType.OPEN_CURLY;
import static groovy.json.JsonTokenType.STRING;
import static groovy.json.JsonTokenType.startingWith;
/**
* The lexer reads JSON tokens in a streaming fashion from the underlying reader.
*
* @author Guillaume Laforge
* @since 1.8.0
*/
public class JsonLexer implements Iterator {
private static final char SPACE = ' ';
private static final char DOT = '.';
private static final char MINUS = '-';
private static final char PLUS = '+';
private static final char LOWER_E = 'e';
private static final char UPPER_E = 'E';
private static final char ZERO = '0';
private static final char NINE = '9';
private final LineColumnReader reader;
/**
* Underlying reader from which to read the JSON tokens.
* This reader is an instance of LineColumnReader,
* to keep track of line and column positions.
*/
public LineColumnReader getReader() {
return reader;
}
private JsonToken currentToken = null;
/**
* Instantiates a lexer with a reader from which to read JSON tokens.
* Under the hood, the reader is wrapped in a LineColumnReader,
* for line and column information, unless it's already an instance of that class.
*
* @param reader underlying reader
*/
public JsonLexer(Reader reader) {
this.reader = reader instanceof LineColumnReader ? (LineColumnReader) reader : new LineColumnReader(reader);
}
/**
* @return the next token from the stream
*/
public JsonToken nextToken() {
try {
int firstIntRead = skipWhitespace();
if (firstIntRead == -1) return null;
char firstChar = (char) firstIntRead;
JsonTokenType possibleTokenType = startingWith((char) firstIntRead);
if (possibleTokenType == null) {
throw new JsonException(
"Lexing failed on line: " + reader.getLine() + ", column: " + reader.getColumn() +
", while reading '" + firstChar + "', " +
"no possible valid JSON value or punctuation could be recognized."
);
}
reader.reset();
long startLine = reader.getLine();
long startColumn = reader.getColumn();
JsonToken token = new JsonToken();
token.setStartLine(startLine);
token.setStartColumn(startColumn);
token.setEndLine(startLine);
token.setEndColumn(startColumn + 1);
token.setType(possibleTokenType);
token.setText("" + firstChar);
if (possibleTokenType.ordinal() >= OPEN_CURLY.ordinal() && possibleTokenType.ordinal() <= FALSE.ordinal()) {
return readingConstant(possibleTokenType, token);
} else if (possibleTokenType == STRING) {
StringBuilder currentContent = new StringBuilder("\"");
// consume the first double quote starting the string
reader.read();
boolean isEscaped = false;
for (;;) {
int read = reader.read();
if (read == -1) return null;
isEscaped = (!isEscaped && currentContent.charAt(currentContent.length() - 1) == '\\');
char charRead = (char) read;
currentContent.append(charRead);
if (charRead == '"' && !isEscaped &&
possibleTokenType.matching(currentContent.toString())) {
token.setEndLine(reader.getLine());
token.setEndColumn(reader.getColumn());
token.setText(unescape(currentContent.toString()));
return token;
}
}
} else if (possibleTokenType == NUMBER) {
StringBuilder currentContent = new StringBuilder();
for (;;) {
reader.mark(1);
int read = reader.read();
if (read == -1) return null;
char lastCharRead = (char) read;
if (lastCharRead >= ZERO && lastCharRead <= NINE ||
lastCharRead == DOT || lastCharRead == MINUS || lastCharRead == PLUS ||
lastCharRead == LOWER_E || lastCharRead == UPPER_E) {
currentContent.append(lastCharRead);
} else {
reader.reset();
break;
}
}
String content = currentContent.toString();
if (possibleTokenType.matching(content)) {
token.setEndLine(reader.getLine());
token.setEndColumn(reader.getColumn());
token.setText(currentContent.toString());
return token;
} else {
throwJsonException(currentContent.toString(), possibleTokenType);
}
}
return null;
} catch (IOException ioe) {
throw new JsonException("An IO exception occurred while reading the JSON payload", ioe);
}
}
private void throwJsonException(String content, JsonTokenType type) {
throw new JsonException(
"Lexing failed on line: " +
reader.getLine() + ", column: " + reader.getColumn() +
", while reading '" + content + "', " +
"was trying to match " + type.getLabel()
);
}
/**
* Replace unicode escape and other control characters with real characters
*
* @param input text
* @return input text without the escaping
*/
public static String unescape(String input) {
return StringEscapeUtils.unescapeJavaScript(input);
}
/**
* When a constant token type is expected, check that the expected constant is read,
* and update the content of the token accordingly.
*
* @param type the token type
* @param token the token
* @return the token updated with end column and text updated
*/
private JsonToken readingConstant(JsonTokenType type, JsonToken token) {
try {
int numCharsToRead = ((String) type.getValidator()).length();
char[] chars = new char[numCharsToRead];
reader.read(chars);
String stringRead = new String(chars);
if (stringRead.equals(type.getValidator())) {
token.setEndColumn(token.getStartColumn() + numCharsToRead);
token.setText(stringRead);
return token;
} else {
throwJsonException(stringRead, type);
}
} catch (IOException ioe) {
throw new JsonException("An IO exception occurred while reading the JSON payload", ioe);
}
return null;
}
/**
* Skips all the whitespace characters and moves the cursor to the next non-space character.
*/
public int skipWhitespace() {
try {
int readChar = 20;
char c = SPACE;
while (Character.isWhitespace(c)) {
reader.mark(1);
readChar = reader.read();
c = (char) readChar;
}
reader.reset();
return readChar;
} catch (IOException ioe) {
throw new JsonException("An IO exception occurred while reading the JSON payload", ioe);
}
}
/**
* Iterator method to know if another token follows,
* or if we've reached the end of the stream.
*
* @return true if there are more tokens
*/
public boolean hasNext() {
currentToken = nextToken();
return currentToken != null;
}
/**
* Iterator method to get the next token of the stream.
*
* @return the next token
*/
public JsonToken next() {
return currentToken;
}
/**
* Method not implemented.
*
* @throws UnsupportedOperationException
*/
public void remove() {
throw new UnsupportedOperationException("The method remove() is not supported on this lexer.");
}
}