Unstable Primefaces fileupload listener call

Question

Having a Spring Boot project working with JDK11, Primefaces 8.0, Spring Boot 2.3.0. deploying it on tomcat 9.0.35. In some deployments my fileupload component is able to trigger the listener method well. In some other, it can't trigger it leaving no error message or log.

I have tried some restarts producing every time same results (fail to upload) with the same build. But despite having not touched the source, another build can make it work.

On another test, I have built & deployed 4-5 times the project with exactly same source code, seeing upload is working in all of them. And for a last test, I just added a space character after a java statement's ';' to change the binary and rebuilt, redeployed and noticed file upload not working.

I can't find out why the behaviour is not stable. I am stuck and have no idea how to debug it, identify the problem. Any suggestion will be welcomed

At pom.xml having:

    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.4</version>
    </dependency>


    <dependency>
       <groupId>com.sun.faces</groupId>
       <artifactId>jsf-api</artifactId>
       <version>2.2.20</version>
    </dependency>
    <dependency>
       <groupId>com.sun.faces</groupId>
       <artifactId>jsf-impl</artifactId>
       <version>2.2.20</version>
    </dependency>

    <dependency>
       <groupId>org.primefaces</groupId>
       <artifactId>primefaces</artifactId>
       <version>8.0</version>
    </dependency>

    <dependency>
        <groupId>com.google.code</groupId>
        <artifactId>kaptcha</artifactId>
        <version>2.3.0</version>
    </dependency>

FileUpload component on page:

<h:form id="bulkDataInsertForm" enctype="multipart/form-data">
  .
  .
    <p:fileUpload id="datafileuploader"
        listener="#{bulkDataInsertBean.handleFileUpload}"
        uploadLabel="upload file"
        cancelLabel="cancel"
        label="choose file"
        update=":bulkDataInsertForm:bulkDataInsertgrowl :bulkDataInsertForm:listFileUploadPanel :bulkDataInsertForm:errorText"
        allowTypes="/(\.|\/)(xlsx)$/"
        sizeLimit="10485760" 
        multiple="false"
        invalidFileMessage="file type error"
        mode="advanced" dragDropSupport="true"
        ajax="true">
    </p:fileUpload>
.
.
</h:form>

I have <h:head> in parent page as told here: How to use PrimeFaces p:fileUpload? Listener method is never invoked or UploadedFile is null / throws an error / not usable.

And ServletInitializer:

@EnableEncryptableProperties
@SpringBootApplication
@ComponentScan({ "com.myapp"  })
public class WebApplication extends SpringBootServletInitializer {  

  @Bean
  public ServletRegistrationBean kaptchaServletRegistration() {
    ServletRegistrationBean bean = new ServletRegistrationBean(new KaptchaServlet(), "/kaptcha.jpg");
    return bean;
  }

  @Bean
  public ServletRegistrationBean facesServletRegistration() {
    ServletRegistrationBean registration = new ServletRegistrationBean<>(new FacesServlet(), "*.xhtml");
    registration.setLoadOnStartup(1);
    return registration;
  }

  @Bean
  public ServletContextInitializer servletContextInitializer() {
    return servletContext -> {
        servletContext.setInitParameter("com.sun.faces.forceLoadConfiguration", Boolean.TRUE.toString());
        servletContext.setInitParameter("primefaces.THEME", "blitzer");
        
        servletContext.setInitParameter("primefaces.CLIENT_SIDE_VALIDATION", Boolean.TRUE.toString());
        
        servletContext.setInitParameter("javax.faces.FACELETS_SKIP_COMMENTS", Boolean.TRUE.toString());
         
        servletContext.setInitParameter("primefaces.FONT_AWESOME", Boolean.TRUE.toString());
        
        servletContext.setInitParameter("javax.faces.ENABLE_CDI_RESOLVER_CHAIN", Boolean.TRUE.toString());
      };


  @Bean
  public ServletListenerRegistrationBean<ConfigureListener> jsfConfigureListener() {
    return new ServletListenerRegistrationBean<>(new ConfigureListener()); 
  }


//for setting fileUploadFilter to in front of filterChain - so uploaded file not consumed by other filter
  @Bean
  public FilterRegistrationBean primeFacesFileUploadFilter() {

     FilterRegistrationBean registration = new FilterRegistrationBean(new org.primefaces.webapp.filter.FileUploadFilter(), facesServletRegistration());
    
     registration.addUrlPatterns("/*"); 
    
     registration.setDispatcherTypes(DispatcherType.REQUEST, DispatcherType.FORWARD);
     registration.setName("primeFacesFileUploadFilter");
     registration.setOrder(1);
     return registration;
    }
  }

Note: On some forums, I have read fileupload filter order can be changed, so some other filters may consume the file stream being uploaded, leaving fileupload filter with no input. It must also accept Forwarded requests. So I added "primeFacesFileUploadFilter" shown above, but it did not help:

This is the order of filterchain during ServletContextInitializer after added the code:

Filter names at FilterChain by order: [requestContextFilter, Tomcat WebSocket (JSR356) Filter, errorPageFilter, primeFacesFileUploadFilter, characterEncodingFilter, springSecurityFilterChain, formContentFilter]

Answer 1

Specifying

servletContext.setInitParameter("primefaces.UPLOADER", "native");    

at servletContextInitializer resulted in sometimes successful and sometimes failing(listener untriggered) fileuploads.

But after specifiying:

servletContext.setInitParameter("primefaces.UPLOADER", "commons"); 

instead of "native", I did nearly 10 builds, deploys, tests in which all fileuploads triggered properly. Of course I can't still guarantee its the absolute solution but its highly likely.