觉得挺好玩的一个问题，如何校验字符串是否为标准的json格式，刚开始的回答是jsonObject或者jsonArray转换一下，如果可以转换，说明为json字符串，如果不能就抛出异常，捕获异常。
但是不让用这种方式。于是查资料从字符串和字符下手。
package com.lsm.util;import java.text.CharacterIterator;import java.text.StringCharacterIterator;/** * 用于校验一个字符串是否是合法的JSON格式 * @author liShuMin * */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\"}"; String jsonStr = "{" + " \"ccobjtypeid\": \"1001\"," + " \"fromuser\": \"李四\"," + " \"touser\": \"张三\"," + " \"desc\": \"描述\"," + " \"subject\": \"主题\"," + " \"attach\": \"3245,3456,4345,4553\"," + " \"data\": {" + " \"desc\": \"测试对象\"," + " \"dataid\": \"22\"," + " \"billno\": \"TEST0001\"," + " \"datarelation\":[" + " {" + " \"dataname\": \"关联对象1\"," + " \"data\": [" + " {" + " \"dataid\": \"22\"," + " \"datalineid\": \"1\"," + " \"content1\": \"test1\"," + " \"content2\": \"test2\"" + " }" + " ]" + " }" + " ]" + " }" + " }"; System.out.println(jsonStr+":"+new JsonValidator().validate(jsonStr)); }}
