How to calculate age from date of birth

Question

I have a user registration form where all user data is stored in database.

I am listing all user data in the UI in a member listing page. In there I have to calculate the age of the user based on their date of birth. I tried by calculating using JSTL, but still I am not getting an answer.

This is what I tried:

<fmt:parseDate value="${user.dateofbirth}" var="parseddate" type="date"  pattern="yyyy-MM-dd" />
  <jsp:useBean id="now" class="java.util.Date" />
    <td class="dataField">
      <fmt:formatDate value="${parseddate}"  type="date" pattern="MMMM dd yyyy "/> 
    </td>
    <c:set var="today" value="<%=new java.util.Date()%>" /> 
    <fmt:parseNumber type="date" value="${today}" />
    <td>
      <c:out value="${today-parseddate}"></c:out>
    </td>
          

I am new to JSTL. Can anyone please help me with this?

Answer 1

If anyone here wants to get the difference between two dates in days and want to display it in another column in the JSP you can you can do like this.

<fmt:parseDate value = "${name_of_your_bean.1st_variable}" var = "formatedDate1" type = "date" pattern = "yyyy-MM-dd" />
<jsp:useBean id="start_date" class="java.util.Date" />  
<td > <fmt:formatDate value = "${formatedDate1}"  type = "date" pattern = "MMMM dd,yyyy"/> </td>
                                                
<fmt:parseDate value = "${name_of_your_bean.2nd_variable}" var = "formatedDate2" type = "date" pattern = "yyyy-MM-dd" />
<jsp:useBean id="end_date" class="java.util.Date" />    
<td> <fmt:formatDate value = "${formatedDate2}"  type = "date" pattern = "MMMM dd,yyyy"/> </td>

                        // To display in separate column do like this                       
<td> <fmt:parseNumber type = "number" integerOnly = "true" value = "${(formatedDate2.time - formatedDate1.time)/(1000 * 60 * 60 * 24)}" /> Days </td> 

Answer 2

Here is code that demonstrates how you might do it with JSTL. It is not exactly perfect because I neglected to account for the extra day in a leap year.

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<fmt:parseDate value="1979-09-27" var="parsedDate" type="date"  pattern="yyyy-MM-dd" />
<jsp:useBean id="now" class="java.util.Date" />  
<fmt:parseNumber type="number" integerOnly = "true" 
    value="${(now.time - parsedDate.time)/(1000 * 60 * 60 * 24 * 365)}" />

Anyway, it outputs 42 years.