日期解析从一种格式转换为另一种格式 [英] Date Parsing from one format to another format

问题描述

我想将日期格式yyyy-mm-dd hh:mm:ss.SSS(以字符串格式存储在数据库中)更改为mm/dd/yyyy进行比较

I want to change date format yyyy-mm-dd hh:mm:ss.SSS ( which is stored in database in string format) to mm/dd/yyyy for their comparison

while(rs.next()) 
    {
        reportBean bean=new reportBean();

        String proj_close_date=rs.getString(3);
        String added_on=rs.getString(4);

        DateFormat myDateFormat = new SimpleDateFormat("MM/dd/yyyy");

        DateFormat myDateFormat1= new SimpleDateFormat("yyyy-mm-dd hh:mm:ss.SSSSSS");

        Date myDate1 = null;    
        Date myDate2 = null;
        Date myDate3 = null;
        Date myDate4 = null;
        Date myDate5 = null;
      try 
        {
          if(proj_close_date==null || proj_close_date.trim().equals(""))
          {
              System.out.println("\n ****** In IF Loop ");
              bean.setCust_code(rs.getString("customer_code"));
              bean.setProject_code(rs.getString("project_code"));
              list.add(bean);
          }
          else
          {
                System.out.println("\n ****** In Else Loop ");
                myDate1 = myDateFormat.parse(proj_close_date);
                myDate2 = myDateFormat.parse(frm_date);
                myDate3 = myDateFormat.parse(to_date);
                myDate5 = myDateFormat1.parse(added_on);                        
                myDate4 = myDateFormat.format(myDate5);

                System.out.println("Project Code ---->"+rs.getString(2));                                           
                System.out.println("Proj_close_date ------>"+myDate1);
                System.out.println("From Date ---->"+myDate2);
                System.out.println("to Date ---->"+myDate3);
                System.out.println("Added_on --->"+myDate4);
                System.out.println("Added_on 1 ie Date 5 ---->"+myDate5);

                if(myDate1.after(myDate2) && myDate1.before(myDate3))  // means --> if(proj_close_date.after(frm_date) && proj_close_date.before(to_date))
                 {                          
                    if(myDate1.after(myDate4))  // means --> if(proj_close_date.after(added_on))
                    {
                        bean.setCust_code(rs.getString("customer_code"));
                        bean.setProject_code(rs.getString("project_code"));
                        list.add(bean);
                    }               
                   else
                   {
                       bean.setCust_code(rs.getString("customer_code"));
                       bean.setProject_code(rs.getString("project_code"));
                       list.add(bean);
                   }  
               }//if    
          }//else

        }//try   
        catch (ParseException e) 
       {
             System.out.println("Invalid Date Parser Exception ");
             e.printStackTrace();
       }


    }
    rs.close();
    stmt.close();

}
catch(SQLException sex)
{
    sex.printStackTrace();
}
finally
{
    closeConnection();
}

推荐答案

一些注意事项

• 约定用于Java类名，每个都有大写的名词， reportBean 变为 ReportBean
• 不要按位置引用SQL列，请始终使用名称代替 rs.getString("customer_code")而不是 rs.getString(3)
• 使用有意义的变量名， myDate1 变为 closeDate
• 实践调试代码，这样就可以消除 System.out.println()
• 优美地释放资源， stmt.close()在finally块内移动
• 使用记录框架，而不是吞下 Exception ，例如 log.error(无效的日期解析器异常"，e);

• convention is for Java class names to have each noun capitalised, reportBean becomes ReportBean
• don't refer to SQL columns by position, always use a name instead rs.getString("customer_code") rather than rs.getString(3)
• use meaningful variable names, myDate1 becomes closeDate
• practice debugging your code so you can eliminate System.out.println()
• gracefully release resources, stmt.close() moves within a finally block
• use a logging framework, rather than swallowing Exception, e.g. log.error("Invalid Date Parser Exception", e);

一些特定的指针:

new SimpleDateFormat("yyyy-mm-dd hh:mm:ss.SSSSSS") // as already noted, mm is the format for minute, MM is the format for month

---

myDate4 = myDateFormat.format(myDate5); // invalid as you are asigning a String to a Date

---

if(myDate1.after(myDate4)) // irrelevant as both if & else block execute the same code

---

rs.close() // not necessary as closed when `Statement` is closed

请参见 Javadoc

您确定数据库架构是所有 varchar 列吗?我建议您修复这种情况.否则，您可以调用

Are you sure that your database schema is all varchar columns? I'd recommend that you fixed that if its the case. Otherwise you can call rs.getDate() instead.

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