Apache POI 在导出可运行 Jar 时极其缓慢

Question

I have performance problems with Apache POI when reading excel files when I export the runnable jar with the Package option from eclipse, not with the Extract required libraries into generated JAR option.

In order to show you the problem, I have created a minimal program. The build.gradle file is:

plugins {
    id 'java'
}

sourceCompatibility = '1.8'

repositories {
    mavenCentral()
}

dependencies {
     compile group: 'org.apache.poi', name: 'poi-ooxml', version: '4.1.2'
}

and the App.java file:

import java.io.File;
import java.io.FileInputStream;

import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class App {

     public static void main(final String[] args) {
        final String excelPath = System.getProperty("user.dir") + "/libro.xlsx"  ;
        try {
            final FileInputStream fis = new FileInputStream(new File(excelPath));
            
            
            final long TIMER = System.currentTimeMillis();
            System.out.println(  "start") ;
            XSSFWorkbook wb = new XSSFWorkbook( fis );
            wb.close();
            System.out.println( "end : " + ( System.currentTimeMillis() - TIMER) + " msec" ) ;
            
            
        } catch (final Exception e) {
            System.out.println("error " + e.getMessage()) ; 
        }
    }
}

When I run the program with an empty excel file, I get the following results on the same machine and with the same files:

• Generated with the Extract option:

   C:\temp>java -jar prueba.jar start end: 603 msec

• Generated with the Package option:

   C:\temp>java -jar prueba.jar start end: 6015 msec

about 10 times more.

What could it be the problem and how can I fix it so that the execution times are similar?

Could anyone help me to find the problem and solve it?

Thank you in advance.

Answer 1

You can look at the difference between the two files using jar tf followed by the archive. It may be that one of the archives is including the signed content, which will mean that upon load, the JVM will verify that the content is the same. You could perhaps see if there is a similar execution time when running with -Xverify:none , although I'd recommend against doing that in a production system.