[BUG] Introduce parser supplier support in FileSystemDocumentLoader

[KaisNeffati]

Issue

#1026

Change

General checklist

• There are no breaking changes
• I have added unit and integration tests for my change
• I have manually run all the unit and integration tests in the module I have added/changed, and they are all green
• I have manually run all the unit and integration tests in the core and main modules, and they are all green

• I have added/updated the documentation
• I have added an example in the examples repo (only for "big" features)

Checklist for adding new model integration

• I have added my new module in the BOM

Checklist for adding new embedding store integration

• I have added a {NameOfIntegration}EmbeddingStoreIT that extends from either EmbeddingStoreIT or EmbeddingStoreWithFilteringIT
• I have added my new module in the BOM

Checklist for changing existing embedding store integration

• I have manually verified that the {NameOfIntegration}EmbeddingStore works correctly with the data persisted using the latest released version of LangChain4j

[langchain4j]

@KaisNeffati thanks a lot!

I am not sure the proposed solution will solve the issue, as:

• Current users already use existing methods of FileSystemDocumentLoader and they will have to change their code to use new methods with suppliers in order to fix the issue
• New users will not necessarily find and use the "correct" new methods with suppliers, so the wrong behavior might still persist for them and be unobvious
• All other parsers are stateless, so having ApacheTikaDocumentParser statefull is counter-intuitive

Instead, I would propose to make ApacheTikaDocumentParser stateless:

• the creation of Parser, ContentHandler and other components should be done in parse method instead of the constructor
• a new constructor should be added. this ctor should accept suppliers of Parser, ContentHandler and other tika components
• existing non-default constructor should be marked as @Deprecated with a comment to use ctor with suppliers instead if user wants to use this parser for multiple files

WDYT? Thanks!

[KaisNeffati]

Yeah ! that's a better approach , I'll update the PR accordingly !

Well seen !

[langchain4j]

@KaisNeffati thank you, good job! Just a few minor comments

[langchain4j]

@KaisNeffati thank you! Good job!