DateTime parsing slow in Spring Boot about spring-boot HOT 4 CLOSED

There's no Spring Boot code involved in this, so I'm not sure what we can do about that?

Also, your approach to benchmarking is flawed. You should use something like JMH.

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This is the Spring code involved:

@Component
public class DatePerformanceTest {
    public DatePerformanceTest() {
        long start = System.currentTimeMillis();
        for (int i = 0; i < 3000000; i++) {
            String dateTime = "2024-03-22T12:34:56.123+00:00";
            ZonedDateTime zonedDateTime = ZonedDateTime.parse(dateTime, ISO_OFFSET_DATE_TIME);
        }
        long end = System.currentTimeMillis();
        System.out.println("Total parse time ms: " + (end - start));

    }
}

from spring-boot.

Measuring the total time it takes to do the parsing should be just fine, We don't need JMH to see that it takes longer time running the parsing code in Spring compared to plain java.

from spring-boot.

This isn't an apples-to-apples comparison and, like @mhalbritter, I don't think it has anything to do with Spring.

When you run the code directly in plain Java, the JVM is in a different state to when the code's run as part of a Spring application. For example, the amount of heap that's available will be different and this will have a knock-on effect on garbage collection. The code that you're measuring creates a significant amount of gargage that has to be collected. When there's less heap available, this collection will have to be performed more often which will slow things down.

You could see this for yourself by running with -verbose:gc and comparing how hard the garbage collector has to work in each case.

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