Fix MalformedInputException on Windows with Java 8 due to charset mis…

[slachiewicz]

…match in stale data cache

Problem

Starting in version 3.11.3, running mvn javadoc:javadoc twice in succession on Windows with Java 8 fails on the second run with:

java.nio.charset.MalformedInputException: Input length = 1
    at org.apache.maven.plugins.javadoc.AbstractJavadocMojo.isUpToDate(AbstractJavadocMojo.java:5008)

This regression affects Windows users running Java 8, where the default platform encoding is Cp1252.

Root Cause

The issue stems from a charset mismatch in how the stale data cache file is written versus how it's read:

1. Write operation (StaleHelper.writeStaleData(), line 126):

   • Uses getDataCharset() which returns Charset.defaultCharset() for Java 8
   • On Windows, this is Cp1252

2. Read operation (AbstractJavadocMojo.isUpToDate(), line 5008):

   • Always uses hardcoded StandardCharsets.UTF_8

When the second run attempts to read a file written with Cp1252 encoding using UTF-8, any non-ASCII bytes cause a MalformedInputException.

Solution

Changed StaleHelper to always save in StandardCharsets.UTF_8 instead of platform-dependent charset. This ensures:

• Consistent encoding across all platforms (Windows, macOS, Linux)
• Consistent encoding across all Java versions (8, 11, 17, 21, etc.)
• Write and read operations use the same charset

Fixes: #1273 #1264