Lewis John McGibbney created NUTCH-3212:
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Summary: Use javac --release 17 when building on JDK 21
Key: NUTCH-3212
URL: https://issues.apache.org/jira/browse/NUTCH-3212
Project: Nutch
Issue Type: Improvement
Components: build
Affects Versions: 1.23
Reporter: Lewis John McGibbney
Fix For: 1.24
Building Nutch on JDK 21 with {{javac.version=17}} ({{{}-source 17 -target
17{}}}) produces a warning on every {{<javac>}} invocation, including one-file
plugin test compiles:
{{warning: [options] system modules path not set in conjunction with -source
17}}
JDK 21 is compiling for language 17 without {{{}--release{}}}, so it uses the
JDK 21 bootstrap classes. That is also why JDK 21 CI reports {{java.net.URL}}
constructor deprecations that do not appear on JDK 17.
A related {{Note}} appears when a processor is found on the classpath:
{{Note: Annotation processing is enabled because one or more processors were
found on the class path.}}
Nutch does not run annotation processors at compile time.
Steps to reproduce
# Use JDK 21.
# {{ant clean compile}} (or CI {{{}tests (jdk 21, …){}}}).
# Inspect javac output for plugin test compiles (e.g.
{{{}protocol-selenium{}}}).
Expected
Quiet compile of Java 17 bytecode (major 61) on both JDK 17 and JDK 21.
Proposed change
In {{build.xml}} and {{{}src/plugin/build-plugin.xml{}}}, replace
{{{}source{}}}/{{{}target="${javac.version}"{}}} with Ant
{{release="${javac.version}"}} ({{{}--release 17{}}}). Optionally add
{{{}-proc:none{}}}. Do not only add {{{}-Xlint:-options{}}}; that hides the
warning and still compiles against JDK 21 APIs.
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