如何实现自动编号？

Question

写一个.properties文件就好了
一个property记录日期，即20041205
一个property记录编号，即02然后写个小程序，判断当前日期和记录日期是否一致，如果一致就将记录编号加1，如果不一致，则将记录编号返回01。然后将记录日期和记录编号字符串连接一下输出就搞定！

Answer 1

这个实现就要先查询数据库，当天的话就在上一个基础上+1，不是当天的就重新开始计,这个编号你可以设置为string类型和int类型的转换，
number= xxxxx; //get from the data base(string )
number=Integer.parseInt)number.subString(11))+1;rightnow=new GregorianCalendar()
SimpleDateFormat pattern = new SimpleDateFormat("yyyyMMdd");
String time=pattern.format(this.rightnow.getTime());
String modelnumber="com"+time+number;

Answer 2

select max[id] as maxid from [dbname] 得到最大的编号maxid
if(!maxid.subString(0,10).equals("com"+(new Date().getYear+1900)+(new Date().getMonth()+1)+new Date().getDate())){
当前id="com"+(new Date().getYear+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
}else{
当前id="com"+(Long.parseLong(maxid.subString(3,12))+1);
}

Answer 3

上面这句
id="com"+(new Date().getYear+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
getYear后面少了() 不好意思

Answer 4

type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                        ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                                                    ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                                                                             ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : method subString (int,int)
location: class java.lang.String
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
         ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
               ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
                                           ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
                                                                    ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:71: cannot resolve symbol
symbol  : method subString (int,int)
location: class java.lang.String
bianhao="com"+(Long.parseLong(maxid.subString(3,12))+1);
                                   ^
8 errors .service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.29 logs.type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                        ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                                                    ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
                                                                                             ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:68: cannot resolve symbol
symbol  : method subString (int,int)
location: class java.lang.String
if(!maxid.subString(0,10).equals("com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate())){
         ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
               ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
                                           ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:69: cannot resolve symbol
symbol  : constructor Date ()
location: class java.sql.Date
bianhao="com"+(new Date().getYear()+1900)+(new Date().getMonth()+1)+new Date().getDate()+"01";
                                                                    ^
An error occurred at line: 9 in the jsp file: /add.jsp
Generated servlet error:
C:\Program Files\Apache Software Foundation\Tomcat 5.0\work\Catalina\localhost\diannao\org\apache\jsp\add_jsp.java:71: cannot resolve symbol
symbol  : method subString (int,int)
location: class java.lang.String
bianhao="com"+(Long.parseLong(maxid.subString(3,12))+1);
                                   ^
8 errors
不好意思，我是新手，刚试过，有问题以上，还请楼上的帮忙解决！有点急！谢谢！！