java自动生成编号的实现(格式：yyMM+四位流水号)

/** * 自动生成编号格式：yyMM+四位流水号 */ @RequestMapping(params = "createCode") @ResponseBody public AjaxJson createCode(HttpServletRequest request, String tableName,  String fieldName) { AjaxJson j = new AjaxJson();  String sql = "select Max(a." + fieldName + ") max_code from "  + tableName + " a ";  List<Map<String, Object>> list = new ArrayList<Map<String, Object>>(); list = jdbcTemplate.queryForList(sql); // System.out.println("最大编号："+list.get(0).get("max_comment_code")); String comment_code = "";  String max_code = ""; if (list.size() > 0) {  max_code = (String) list.get(0).get("max_code"); }  SimpleDateFormat format = new SimpleDateFormat("yyMM"); // 时间字符串产生方式 String uid_pfix = format.format(new Date()); // 组合流水号前一部分，时间字符串，如：1601 System.out.println("time=" + format.format(new Date())); if (max_code != null && max_code.contains(uid_pfix)) {  String uid_end = max_code.substring(4, 8); // 截取字符串最后四位，结果:0001  // System.out.println("uid_end=" + uid_end);  int endNum = Integer.parseInt(uid_end); // 把String类型的0001转化为int类型的1  // System.out.println("endNum=" + endNum);  int tmpNum = 10000 + endNum + 1; // 结果10002  // System.out.println("tmpNum=" + tmpNum);  comment_code = uid_pfix + UtilMethod.subStr("" + tmpNum, 1);// 把10002首位的1去掉，再拼成1601260002字符串 } else {  comment_code = uid_pfix + "0001"; } // System.out.println(comment_code);  Map<String, Object> map = new HashMap<String, Object>(); map.put("msg", comment_code); j.setAttributes(map); return j; } //公共方法public class UtilMethod {   /*  * 把10002首位的1去掉的实现方法：  * @param str  * @param start  * @return  */ public static String subStr(String str, int start) {     if (str == null || str.equals("") || str.length() == 0)       return "";     if (start < str.length()) {       return str.substring(start);     } else {       return "";     }    }}

//自动生成编号；格式：yyMM0001function createCode() {  var id = $("[name='id']").val();  // alert(id.length);   if(id.length<=0){  var a="";  $.ajax({   async : false,   cache : false,   type : 'POST',   contentType : 'application/json',    dataType:"json",   url : "Controller.do?createCode&tableName=表名&fieldName=字段名",   error : function() {   alert('出错了');   frameElement.api.close();   },   success : function(data) {   a=data.attributes.msg;   }     }); //alert(a);    $("#check_task_code").val(a);   } }