The Groovy JsonSlurper.java source code
/*
* Copyright 2003-2011 the original author or authors.
*
* 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 groovy.json;
import static groovy.json.JsonTokenType.*;
import groovy.io.LineColumnReader;
import java.io.Reader;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* JSON slurper which parses text or reader content into a data structure of lists and maps.
* <p>
* Example usage:
* <code> * def slurper = new JsonSlurper()
* def result = slurper.parseText('{"person":{"name":"Guillaume","age":33,"pets":["dog","cat"]}}')
*
* assert result.person.name == "Guillaume"
* assert result.person.age == 33
* assert result.person.pets.size() == 2
* assert result.person.pets[0] == "dog"
* assert result.person.pets[1] == "cat"
* </pre>
*
* @author Guillaume Laforge
* @since 1.8.0
*/
public class JsonSlurper {
/**
* Parse a text representation of a JSON data structure
*
* @param text JSON text to parse
* @return a data structure of lists and maps
*/
public Object parseText(String text) {
if (text == null || text.length() == 0) {
throw new IllegalArgumentException("The JSON input text should neither be null nor empty.");
}
return parse(new LineColumnReader(new StringReader(text)));
}
/**
* Parse a JSON data structure from content from a reader
*
* @param reader reader over a JSON content
* @return a data structure of lists and maps
*/
public Object parse(Reader reader) {
Object content;
JsonLexer lexer = new JsonLexer(reader);
JsonToken token = lexer.nextToken();
if (token.getType() == OPEN_CURLY) {
content = parseObject(lexer);
} else if (token.getType() == OPEN_BRACKET) {
content = parseArray(lexer);
} else {
throw new JsonException(
"A JSON payload should start with " + OPEN_CURLY.getLabel() +
" or " + OPEN_BRACKET.getLabel() + ".\n" +
"Instead, '" + token.getText() + "' was found " +
"on line: " + token.getStartLine() + ", " +
"column: " + token.getStartColumn()
);
}
return content;
}
/**
* Parse an array from the lexer
*
* @param lexer the lexer
* @return a list of JSON values
*/
private List parseArray(JsonLexer lexer) {
List content = new ArrayList();
JsonToken currentToken;
for(;;) {
currentToken = lexer.nextToken();
if (currentToken == null) {
throw new JsonException(
"Expected a value on line: " + lexer.getReader().getLine() + ", " +
"column: " + lexer.getReader().getColumn() + ".\n" +
"But got an unterminated array."
);
}
if (currentToken.getType() == OPEN_CURLY) {
content.add(parseObject(lexer));
} else if (currentToken.getType() == OPEN_BRACKET) {
content.add(parseArray(lexer));
} else if (currentToken.getType().ordinal() >= NULL.ordinal()) {
content.add(currentToken.getValue());
} else if (currentToken.getType() == CLOSE_BRACKET) {
return content;
} else {
throw new JsonException(
"Expected a value, an array, or an object " +
"on line: " + currentToken.getStartLine() + ", " +
"column: " + currentToken.getStartColumn() + ".\n" +
"But got '" + currentToken.getText() + "' instead."
);
}
currentToken = lexer.nextToken();
if (currentToken == null) {
throw new JsonException(
"Expected " + CLOSE_BRACKET.getLabel() + " " +
"or " + COMMA.getLabel() + " " +
"on line: " + lexer.getReader().getLine() + ", " +
"column: " + lexer.getReader().getColumn() + ".\n" +
"But got an unterminated array."
);
}
// Expect a comma for an upcoming value
// or a closing bracket for the end of the array
if (currentToken.getType() == CLOSE_BRACKET) {
break;
} else if (currentToken.getType() != COMMA) {
throw new JsonException(
"Expected a value or " + CLOSE_BRACKET.getLabel() + " " +
"on line: " + currentToken.getStartLine() + " " +
"column: " + currentToken.getStartColumn() + ".\n" +
"But got '" + currentToken.getText() + "' instead."
);
}
}
return content;
}
/**
* Parses an object from the lexer
*
* @param lexer the lexer
* @return a Map representing a JSON object
*/
private Map parseObject(JsonLexer lexer) {
Map content = new HashMap();
JsonToken previousToken = null;
JsonToken currentToken = null;
for(;;) {
currentToken = lexer.nextToken();
if (currentToken == null) {
throw new JsonException(
"Expected a String key on line: " + lexer.getReader().getLine() + ", " +
"column: " + lexer.getReader().getColumn() + ".\n" +
"But got an unterminated object."
);
}
// expect a string key, or already a closing curly brace
if (currentToken.getType() == CLOSE_CURLY) {
return content;
} else if (currentToken.getType() != STRING) {
throw new JsonException(
"Expected " + STRING.getLabel() + " key " +
"on line: " + currentToken.getStartLine() + ", " +
"column: " + currentToken.getStartColumn() + ".\n" +
"Bug got '" + currentToken.getText() + "' instead."
);
}
String mapKey = (String) currentToken.getValue();
currentToken = lexer.nextToken();
if (currentToken == null) {
throw new JsonException(
"Expected a " + COLON.getLabel() + " " +
"on line: " + lexer.getReader().getLine() + ", " +
"column: " + lexer.getReader().getColumn() + ".\n" +
"But got an unterminated object."
);
}
// expect a colon between the key and value pair
if (currentToken.getType() != COLON) {
throw new JsonException(
"Expected " + COLON.getLabel() + " " +
"on line: " + currentToken.getStartLine() + ", " +
"column: " + currentToken.getStartColumn() + ".\n" +
"Bug got '" + currentToken.getText() + "' instead."
);
}
currentToken = lexer.nextToken();
if (currentToken == null) {
throw new JsonException(
"Expected a value " +
"on line: " + lexer.getReader().getLine() + ", " +
"column: " + lexer.getReader().getColumn() + ".\n" +
"But got an unterminated object."
);
}
// value can be an object, an array, a number, string, boolean or null values
if (currentToken.getType() == OPEN_CURLY) {
content.put(mapKey, parseObject(lexer));
} else if (currentToken.getType() == OPEN_BRACKET) {
content.put(mapKey, parseArray(lexer));
} else if (currentToken.getType().ordinal() >= NULL.ordinal()) {
content.put(mapKey, currentToken.getValue());
} else {
throw new JsonException(
"Expected a value, an array, or an object " +
"on line: " + currentToken.getStartLine() + ", " +
"column: " + currentToken.getStartColumn() + ".\n" +
"But got '" + currentToken.getText() + "' instead."
);
}
previousToken = currentToken;
currentToken = lexer.nextToken();
// premature end of the object
if (currentToken == null) {
throw new JsonException(
"Expected " + CLOSE_CURLY.getLabel() + " or " + COMMA.getLabel() + " " +
"on line: " + previousToken.getEndLine() + ", " +
"column: " + previousToken.getEndColumn() + ".\n" +
"But got an unterminated object."
);
}
// Expect a comma for an upcoming key/value pair
// or a closing curly brace for the end of the object
if (currentToken.getType() == CLOSE_CURLY) {
break;
} else if (currentToken.getType() != COMMA) {
throw new JsonException(
"Expected a value or " + CLOSE_CURLY.getLabel() + " " +
"on line: " + currentToken.getStartLine() + ", " +
"column: " + currentToken.getStartColumn() + ".\n" +
"But got '" + currentToken.getText() + "' instead."
);
}
}
return content;
}
}
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