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What is the DocumentLoader API in LangChain4j and what sources does it support?

Document loaders are the entry point of any RAG ingestion pipeline — they read raw content from a source and return it as a list of Document objects, each containing the text content and source metadata. LangChain4j's loaders all implement the DocumentLoader interface and populate the Document.metadata() map with source-specific information like file path, URL, or S3 key.

Built-in document loader sources include:

LangChain4j Built-in Document Loaders
LoaderSourceNotes
FileSystemDocumentLoaderLocal files and directoriesSupports glob patterns; auto-detects parser by extension
UrlDocumentLoaderHTTP/HTTPS URLsFetches and parses web pages
ClassPathDocumentLoaderClasspath resourcesGood for embedded documentation in JARs
AmazonS3DocumentLoaderAWS S3 bucketsVia langchain4j-document-loader-amazon-s3
AzureBlobStorageDocumentLoaderAzure Blob StorageVia langchain4j-document-loader-azure-storage-blob
GitHubDocumentLoaderGitHub repositoriesLoads files from a repo branch

Document parsers handle format-specific extraction: TextDocumentParser for plain text, ApachePdfBoxDocumentParser for PDFs, ApacheTikaDocumentParser for Word/Excel/PowerPoint and 100+ other formats. Parsers are composable with loaders:

// Load all PDFs from a directory
List<Document> docs = FileSystemDocumentLoader.loadDocuments(
    "./knowledge-base",
    PathMatcher.of("glob:**.pdf"),
    new ApachePdfBoxDocumentParser()
);

Which LangChain4j document parser handles Word, Excel, and PowerPoint files along with 100+ other formats?

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