Java对json是否合法进行格式校验详解编程语言

/** 
 * 用于校验一个字符串是否是合法的JSON格式 
 * 
 */ 
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.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; 
    } 
    public static void main(String[] args){ 
        String jsonStr = "{/"website/":/"open-open.com/"}"; 
        System.out.println(jsonStr+":"+new JsonValidator().validate(jsonStr)); 
    } 
}