最近项目中遇到JSON格式验证的问题，由于请求接口中可能存在新旧版本兼容问题，老版本的客户端，情况就不说了，糟透了，各种格式都有，看起来像JSON，但是……呵呵。

所以需要做兼容，就得把之前不规范的东西规范一下，并且验证其正确性；工具类如下：

/**   * Project Name:v3a-b2c   * File Name:JsonValidator.java   * Package Name:com.v3a.util   * Date:2014年10月26日下午1:59:59   * Copyright (c) 2014, chenzhou1025@126.com All Rights Reserved.   *  */     package com.v3a.util;  import java.text.CharacterIterator;  import java.text.StringCharacterIterator;  import java.util.List;  import java.util.regex.Pattern;     import org.apache.commons.lang.StringUtils;     import com.google.common.collect.Lists;  /**   * ClassName:JsonValidator <br/>   * Function: 用于校验一个字符串是否是合法的JSON格式. <br/>   * Date:     2014年10月26日 下午1:59:59 <br/>   * 用法：    new JsonValidator().validate(“JOSN字符串”)   * @author   勋辉   * @version     * @since    JDK 1.7   * @see      */  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) {          /**           * 兼容不规范的JSON格式(使用单引号的方式),将单引号替换为双引号           */          input =formartJson(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 json ="{firstName : Brett, 'lastName':'McLaughlin', 'email': 'aaaa'}";          boolean valid = new JsonValidator().valid(json);          System.out.println(valid);      }             public static String  formartJson(String json) {          String replaceAll = json.trim().replaceAll("'", "\"").replace(" ", "");          char[] charArray = replaceAll.toCharArray();          String regEx = "^[A-Za-z]+$";          Pattern pat = Pattern.compile(regEx);          List<Integer> list = Lists.newLinkedList();          StringBuilder builder = new StringBuilder(replaceAll);          for (int i = 0; i < charArray.length-1; i++) {              if (i < charArray.length) {                  String current = String.valueOf(charArray[i]).trim();                  if(StringUtils.isEmpty(current.trim())){                      builder.deleteCharAt(i);                      continue;                  }else{                      boolean flagcurrent = pat.matcher(current).find();                      String last = String.valueOf(charArray[i + 1]).trim();                      boolean flaglast = pat.matcher(last).find();                      /*                       * 如果当前是标点，则是false，如果是字母则是true，下一个(last)是字母的，则继续，如果是标点则检查是不是双引号，                       * 不是则记下标志位                       */                      if (flagcurrent) {                          if (!flaglast) {                              if (!check(last))                                  list.add(i+1);                          }                      }else{                          /*                           * 如果当前不是标点，则检查下一个(last)是不是字符串，如果是，则看当前标点是不是双引号，不是，则记录位置                           * 如果当前不是字符串并且last是字符串的情况下，检查当前是不是引号                           *                            */                          if(!flagcurrent&&flaglast){                              if(!check(current)) {                                  list.add(i+1);                              }                          }                      }                                     }              }          }          //StringBuilder builder = new StringBuilder(replaceAll);          for (int i = 0; i < list.size(); i++) {              builder.insert(list.get(i)+i, "\"");          }          return builder.toString();      }                /**       * 检查字符是不是JSON中的标准标点       * check       * @author 勋辉       * @param checkString       * @return       * @since JDK 1.7       */      public static boolean check(String checkString) {          boolean flag = true;          switch (checkString) {          case "{":              flag = false;              break;          case "}":              flag = false;              break;          case "[":              flag = false;              break;          case ",":              flag = false;              break;          case ":":              flag = false;              break;          case "\"":              flag = true;              break;          }          return flag;      }  }