Add JPMS compatibility to Jackson JSON 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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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.