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3.x to 4.x Multipart Mode Change
The underlying httpcomponents client library was upgraded to 5.x version, where the modes were changed to:
- LEGACY
- STRICT
- EXTENDED
The differences between httpcomponents client library version 4.x and 5.x is explained by Claude AI below.
I'll analyze the different multipart modes across HttpComponents 4.x and 5.x versions.
HttpComponents 4.x modes:
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BROWSER_COMPATIBLE: This mode aimed to mimic browser behavior for multipart form submissions. It used platform-specific line endings (CRLF on Windows, LF on Unix) and had special handling for filenames to ensure compatibility with various browsers.
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STRICT: This mode followed a strict interpretation of the original multipart specification (RFC 2046). It used CRLF line endings regardless of platform and had stricter encoding rules.
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RFC_6532: This mode implemented RFC 6532 which extended MIME format to allow UTF-8 encoding in header fields. This was particularly useful for handling non-ASCII filenames and form field names.
HttpComponents 5.x modes:
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LEGACY: This is effectively the replacement for BROWSER_COMPATIBLE mode, maintaining backward compatibility for applications that need browser-like behavior. However, it has been renamed to better reflect its purpose as a legacy compatibility mode rather than suggesting current browser behavior.
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STRICT: This mode remains similar to 4.x's STRICT mode, continuing to follow RFC 2046 specifications strictly.
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EXTENDED: This is the evolution of RFC_6532 mode, supporting modern MIME specifications including UTF-8 encoding in headers. The name change reflects that it now encompasses more than just RFC 6532 compliance, including other modern MIME-related RFCs and extensions.
The main changes in 5.x were:
- Renaming BROWSER_COMPATIBLE to LEGACY to better reflect its purpose
- Renaming RFC_6532 to EXTENDED to indicate broader modern MIME support
- Overall modernization of the implementation while maintaining backwards compatibility through the LEGACY mode
I should note that while I aim to be accurate, you should verify these specific details against the official HttpComponents documentation, especially for recent changes.