Json串校验

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import java.text.CharacterIterator;import java.text.StringCharacterIterator;public class JsonValidator {    private CharacterIterator it;    private char c;    private int col;    public JsonValidator() {    }    /**     * @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.DONE; t = 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.DONE; nextCharacter()) {            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;    }}
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