Add JPMS compatibility to Jackson JSON 2 mapper by configuring ObjectMapper to work without --add-opens JVM flags. #754
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Configure ObjectMapper with JPMS-compatible settings: - Disable CAN_OVERRIDE_ACCESS_MODIFIERS to prevent setAccessible() calls - Add ParameterNamesModule to discover constructor parameter names from bytecode instead of reflection This allows applications using the MCP SDK to operate without `--add-opens` JVM flags, enabling full JPMS module encapsulation. The SDK already compiles with `-parameters` flag, which is required for ParameterNamesModule to function. Signed-off-by: Nicholas Walter Knize <nknize@apache.org>
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Rebased to Jackson 2 due to the recent Jackson 3 merge. Some projects still have transitive dependencies on Jackson 2 and can't rely on a Jackson 3 migration. This retains JPMS support for Jackson 2. |
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Motivation and Context
Applications using the MCP Java SDK with JPMS (Java Platform Module System) currently require --add-opens JVM flags because the Jackson ObjectMapper uses setAccessible() to access record constructors. This breaks module encapsulation and prevents full JPMS adoption.
This change configures the ObjectMapper to:
CAN_OVERRIDE_ACCESS_MODIFIERSto preventsetAccessible()callsParameterNamesModuleto discover constructor parameter names from bytecodeThe SDK already compiles with
-parameters, so no additional build configuration is needed.How Has This Been Tested?
JpmsCompatibilityTeststhat verify record deserialization works without reflectionCAN_OVERRIDE_ACCESS_MODIFIERSis disabled via configuration testBreaking Changes
None. This is a transparent configuration change. Applications that previously worked will continue to work, and applications that required
--add-opensflags can now remove them.Types of changes
Checklist
Additional context
Resolves #753
The
ParameterNamesModuledependency is already transitively available via Jackson, but is now explicitly declared inpom.xmlfor clarity.