[#BATCH-174] Pluggable file-access for input and output

Spring Batch

Pluggable file-access for input and output

Created: 17/Oct/07 12:13 PM Updated: 01/Oct/08 08:31 AM

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~~BATCH-21~~ OutputResource abstraction for file / stream output

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The Apache Commons is Virtual File System (VFS) module is an abstraction layer over various "file systems" - i.e. ZIP, SFTP, in-memory, HTTP, CIFS-Samba, MIME, etc. The file system providers are pluggable (like a 3-rd party VFS-plugin for EMC Documentum).

The VFS could give support for different file-system types in the processors, but also in providers.

My suggestion is to support both the Spring Resource abstraction (as it is currently) and the VFS with wrappers that would adapt the file-access technologies to a common interface.
The Spring-Resource / VFS would be injectable into the flat-file and XML providers / processors.

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Dave Syer added a comment - 30/Oct/07 06:15 AM

If the Commons VFS is compatible with Spring Resource I would prefer to see a Resource implementation wrapping VFS, rather than supporting multiple abstractions. Spring Modules might be a good place to seed that idea.

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tomi vanek added a comment - 31/Oct/07 01:39 AM

I have the impression that the Spring Resource solution focuses just on the input. I did not find the interfaces for output in the Spring API - there is an InputStreamResource, but there is not an OutputStreamResource. And additional complication for batch providers and processors is that the Spring resources do not have the getPointer() and seek() functionality in the interface declaration (i.e. for setting the pointer to the last commited position by batch job restarting).

But I agree - the definition of a universal input and output channel / interface with getPointer() and seek() functionality is out-of-scope for Spring Batch project.

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Dave Syer added a comment - 31/Oct/07 05:55 PM

This is not an exact duplicate of ~~BATCH-21~~, but I'm going to mark it as such and resolve because there isn't anything we want to do in Spring Batch to support external implementations of Resource abstractions. An internal abstraction for output resources is still on hte table (hence ~~BATCH-21~~ is still open).