json文件java校验_java 校验json格式

/**

* 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\":\"oschina.net\"}";

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

}

}

该文章转自：http://www.sharejs.com/codes/java/5955