8328894: HttpResponse.body() returns null with https target and failed proxy authentication

[ehs208]

Summary

This patch addresses the issue where HttpResponse.body() returns null for 407 responses when using HTTPS through a proxy, while HTTP requests correctly return the response body.

Problem

When an HTTPS request receives a 407 Proxy Authentication Required response, the response body is discarded during CONNECT tunnel establishment. This is inconsistent with HTTP behavior where the body is properly returned.

Root cause:

• HTTPS uses MultiExchange<Void> for CONNECT requests
• The body is explicitly ignored via ignoreBody() on 407 responses
• No mechanism exists to preserve the body for later retrieval

Proposed Solution

I propose the following changes to preserve and return the 407 response body:

1. PlainTunnelingConnection.java: Change MultiExchange<Void> to MultiExchange<byte[]> and read the body on 407 responses instead of ignoring it

2. ProxyAuthenticationRequired.java: Add proxyResponseBody field to carry the body bytes through the exception

3. Exchange.java: Cache both the proxy response and body, then return them when the application calls body()

Testing

Added comprehensive test (ProxyAuthHttpTest.java) covering:

• Basic HTTP and HTTPS 407 responses
• Multiple BodyHandler types: ofString(), ofByteArray(), ofInputStream(), ofLines()
• Response headers validation

Test results: 38/38 passed

Notes

• This change only affects 407 responses; all other flows remain unchanged
• The cached body is cleared after first use to prevent reuse
• No changes to public APIs; internal implementation only

I'd appreciate any feedback on this approach. If there's a better way to handle this, I'm happy to revise.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8328894: HttpResponse.body() returns null with https target and failed proxy authentication (Bug - P3)

Reviewing

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