import java.text.CharacterIterator

import java.text.StringCharacterIterator

public class JsonValidator {

private CharacterIterator it

private char c

private int col

public JsonValidator(){

}

/**

* 验证一个字符串是否是合法的JSON串

*

* @param input 要验证的字符串

* @return true-合法 ，false-非法

*/

public boolean validate(String input) {

input = input.trim()

boolean ret = valid(input)

return ret

}

private boolean valid(String input) {

if ("".equals(input)) return true

boolean ret = true

it = new StringCharacterIterator(input)

c = it.first()

col = 1

if (!value()) {

ret = error("value", 1)

} else {

skipWhiteSpace()

if (c != CharacterIterator.DONE) {

ret = error("end", col)

}

}

return ret

}

private boolean value() {

return literal("true") || literal("false") || literal("null") || string() || number() || object() || array()

}

private boolean literal(String text) {

CharacterIterator ci = new StringCharacterIterator(text)

char t = ci.first()

if (c != t) return false

int start = col

boolean ret = true

for (t = ci.next()t != CharacterIterator.DONEt = ci.next()) {

if (t != nextCharacter()) {

ret = false

break

}

}

nextCharacter()

if (!ret) error("literal " + text, start)

return ret

}

private boolean array() {

return aggregate('[', ']', false)

}

private boolean object() {

return aggregate('{', '}', true)

}

private boolean aggregate(char entryCharacter, char exitCharacter, boolean prefix) {

if (c != entryCharacter) return false

nextCharacter()

skipWhiteSpace()

if (c == exitCharacter) {

nextCharacter()

return true

}

for () {

if (prefix) {

int start = col

if (!string()) return error("string", start)

skipWhiteSpace()

if (c != ':') return error("colon", col)

nextCharacter()

skipWhiteSpace()

}

if (value()) {

skipWhiteSpace()

if (c == ',') {

nextCharacter()

} else if (c == exitCharacter) {

break

} else {

return error("comma or " + exitCharacter, col)

}

} else {

return error("value", col)

}

skipWhiteSpace()

}

nextCharacter()

return true

}

private boolean number() {

if (!Character.isDigit(c) &&c != '-') return false

int start = col

if (c == '-') nextCharacter()

if (c == '0') {

nextCharacter()

} else if (Character.isDigit(c)) {

while (Character.isDigit(c))

nextCharacter()

} else {

return error("number", start)

}

if (c == '.') {

nextCharacter()

if (Character.isDigit(c)) {

while (Character.isDigit(c))

nextCharacter()

} else {

return error("number", start)

}

}

if (c == 'e' || c == 'E') {

nextCharacter()

if (c == '+' || c == '-') {

nextCharacter()

}

if (Character.isDigit(c)) {

while (Character.isDigit(c))

nextCharacter()

} else {

return error("number", start)

}

}

return true

}

private boolean string() {

if (c != '"') return false

int start = col

boolean escaped = false

for (nextCharacter()c != CharacterIterator.DONEnextCharacter()) {

if (!escaped &&c == '\\') {

escaped = true

} else if (escaped) {

if (!escape()) {

return false

}

escaped = false

} else if (c == '"') {

nextCharacter()

return true

}

}

return error("quoted string", start)

}

private boolean escape() {

int start = col - 1

if (" \\\"/bfnrtu".indexOf(c) <0) {

return error("escape sequence \\\",\\\\,\\/,\\b,\\f,\\n,\\r,\\t or \\uxxxx ", start)

}

if (c == 'u') {

if (!ishex(nextCharacter()) || !ishex(nextCharacter()) || !ishex(nextCharacter())

|| !ishex(nextCharacter())) {

return error("unicode escape sequence \\uxxxx ", start)

}

}

return true

}

private boolean ishex(char d) {

return "0123456789abcdefABCDEF".indexOf(c) >= 0

}

private char nextCharacter() {

c = it.next()

++col

return c

}

private void skipWhiteSpace() {

while (Character.isWhitespace(c)) {

nextCharacter()

}

}

private boolean error(String type, int col) {

System.out.printf("type: %s, col: %s%s", type, col, System.getProperty("line.separator"))

return false

}

public static void main(String[] args){

String jsonStr = "{\"website\":\"open-open.com\"}"

System.out.println(jsonStr+":"+new JsonValidator().validate(jsonStr))

}

}