display Date diff in jsp

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I have a date field in database which store just date without time. Now I want to know the number of days difference in current date and my date field while displaying that

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礼貌的吻别

2021-01-13 07:01

  Calendar calendar1 = Calendar.getInstance();
  Calendar calendar2 = Calendar.getInstance();
  calendar1.set(2007, 01, 10);
  calendar2.set(2007, 07, 01);

  long milliseconds1 = calendar1.getTimeInMillis();
  long milliseconds2 = calendar2.getTimeInMillis();
  long diff = milliseconds2 - milliseconds1;
  long diffSeconds = diff / 1000;
  long diffMinutes = diff / (60 * 1000);
  long diffHours = diff / (60 * 60 * 1000);
  long diffDays = diff / (24 * 60 * 60 * 1000);

  System.out.println("\nThe Date Different Example");
  System.out.println("Time in milliseconds: " + diff + " milliseconds.");
  System.out.println("Time in seconds: " + diffSeconds + " seconds.");
  System.out.println("Time in minutes: " + diffMinutes + " minutes.");
  System.out.println("Time in hours: " + diffHours + " hours.");
  System.out.println("Time in days: " + diffDays + " days.");

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甜味超标

2021-01-13 07:11

You can try something like this:-

<html>
<head>
<script>
function dateDiff(dateform) {
date1 = new Date();
date2 = new Date();

date1temp = new Date(dateform.firstdate.value);
date1.setTime(date1temp.getTime());

date2temp = new Date(dateform.seconddate.value);
date2.setTime(date2temp.getTime());

timediff = Math.abs(date1.getTime() - date2.getTime());
days = Math.floor(timediff / (1000 * 60 * 60 * 24)); 
dateform.difference.value = days;
return false; 
}
</script>
</head>

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天涯浪人

2021-01-13 07:14

There's nothing like that in standard JSTL. A custom EL function would be your best bet.

First implement some static methods which performs the job:

public final class Functions {

    private Functions() {}

    public static int daysBetween(Date before, Date after) {
        // ...
    }

    public static int daysUntilToday(Date date) {
        // ...
    }

}

If you register it as follows in /WEB-INF/functions.tld:

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">

    <tlib-version>1.0</tlib-version>
    <short-name>Custom_Functions</short-name>
    <uri>http://example.com/functions</uri>

    <function>
        <name>daysBetween</name>
        <function-class>com.example.Functions</function-class>
        <function-signature>boolean daysBetween(java.util.Date, java.util.Date)</function-signature>
    </function>
    <function>
        <name>daysUntilToday</name>
        <function-class>com.example.Functions</function-class>
        <function-signature>boolean daysUntilToday(java.util.Date)</function-signature>
    </function>
</taglib>

then you'll be able to use it as follows, provided that #{bean.date} returns a fullworthy java.util.Date:

<%@taglib uri="http://example.com/functions" prefix="f" %>

${f:daysUntilToday(bean.date)} days

The implementation is free to your choice. I'd personally prefer Joda Time:

public static int daysBetween(Date before, Date after) {
    return Days.daysBetween(new DateTime(before.getTime()), new DateTime(after.getTime())).getDays();
}

public static int daysUntilToday(Date date) {
    return Days.daysBetween(new DateTime(date.getTime()), new DateTime()).getDays();
}

Or if you're restricted to standard Java API, fall back to the well known Calendar boilerplate (unfortunately, JSR-310 didn't made it into Java 7, we've to wait for Java 8):

public static int daysBetween(Date before, Date after) {
    Calendar c1 = createCalendarWithoutTime(before);
    Calendar c2 = createCalendarWithoutTime(after);
    int days = 0;

    for (;c1.before(c2); days++) {
        c1.add(Calendar.DATE, 1);
    }

    return days;
}

public static int daysUntilToday(Date date) {
    return daysBetween(date, new Date());
}

private static Calendar createCalendarWithoutTime(Date date) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.set(Calendar.MINUTE, 0);
    calendar.set(Calendar.SECOND, 0);
    calendar.set(Calendar.MILLISECOND, 0);
    return calendar;
}

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