- /**
- * 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(d) >= 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\\":\\"CodeSnippet.Cn\\"}";
- System.out.println(jsonStr+":"+new JsonValidator().validate(jsonStr));
- }
- }
- //该片段来自于http://www.codesnippet.cn/detail/210320149091.html
来源: http://www.codesnippet.cn/detail/210320149091.html