/**
* 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;
}
/**
* 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"
+ "But 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"
+ "But 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;
}
/**
* 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;
}
