如何配置FileEntityStoreService？激活时遇除零异常问询

Got it, let's tackle this issue head-on. The root problem here is that the slices configuration property for FileEntityStoreService isn't being applied correctly—your assumption about a default value of 1 is spot-on, but in your current setup, that default isn't kicking in, leading to a division-by-zero when the store tries to calculate entity file paths.

Here are two straightforward, reliable ways to fix this:

1. Explicitly Set Defaults in Your Assembly Code #

You can define the default slices value directly when assembling the FileEntityStoreAssembler. Modify your code to add a withDefaults block that explicitly sets slices to 1:

import org.apache.polygene.api.common.Visibility;
import org.apache.polygene.api.structure.Application;
import org.apache.polygene.bootstrap.Energy4Java;
import org.apache.polygene.entitystore.file.assembly.FileEntityStoreAssembler;
import org.apache.polygene.index.rdf.assembly.RdfNativeSesameStoreAssembler;
import org.apache.polygene.library.fileconfig.FileConfigurationAssembler;

public class FileStoreException {
    public static void main(String[] args) throws Exception {
        Energy4Java polygene = new Energy4Java();
        Application application = polygene.newApplication(factory -> factory.newApplicationAssembly(
            module -> {
                new FileConfigurationAssembler()
                    .visibleIn(Visibility.application)
                    .assemble(module);
                // Add this withDefaults block to set the slices default
                new FileEntityStoreAssembler()
                    .withConfig(module, Visibility.application)
                    .withDefaults(properties -> properties.set("slices", 1)) // <-- Fix right here
                    .assemble(module);
                new RdfNativeSesameStoreAssembler()
                    .withConfig(module, Visibility.application)
                    .assemble(module);
                module.defaultServices();
            }) 
        );
        application.activate();
    }
}

This guarantees that even if no external configuration is present, the slices value will default to 1, eliminating the division-by-zero error during activation.

2. Use a Configuration Properties File #

Since you're already using FileConfigurationAssembler, you can externalize the setting with a properties file. Create a file named filestore.properties (place it in your classpath root, or configure the file assembler to point to its path) with this line:

org.apache.polygene.entitystore.file.slices=1

This approach is ideal if you want to keep configuration separate from your codebase, making it easier to adjust values later without recompiling.

Why This Fixes the Issue #

Looking at your stack trace, the error occurs in FileEntityStoreMixin.getDataFile() where the code divides by the slices value to map entities to their storage files. By setting slices to a positive integer (1 is the intended default), you avoid the invalid division-by-zero scenario. The default value should be applied automatically, but in your setup, the config initialization wasn't picking it up—explicitly setting it closes that gap.

内容的提问来源于stack exchange，提问作者Nina