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feat: Introduce McpJsonMapper interface to decouple from Jackson (#543)

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This pull request creates two modules, `mcp-json` and `mcp-json-jackson`. It removes the `com.fasterxml.jackson.core:jackson-databind` and `com.networknt:json-schema-validator` dependencies from the `mcp` module. The `mcp` module now only depends on `com.fasterxml.jackson.core:jackson-annotations`.

To use Jackson, you have to add `mcp-jackson` to your dependencies in addition to `mcp`. I added the dependency `mcp-jackson` to both `mcp-spring-mvc` and `mcp-spring-webflux` to avoid a breaking change in those modules.

It provides two [SPI](https://docs.oracle.com/javase/tutorial/sound/SPI-intro.html) `JsonSchemaValidatorSupplier` and `JacksonJsonSchemaValidatorSupplier` to allow easy replacement for consumers who don't want to use Jackson.

This pull request also ensures no `McpJsonMapper` is instantiated if one is provided via a builder method. Only if the builders don't receive a `McpJsonMapper` mapper, one is instantiated in the `build` method of the builder.
The logic behind this is to allow frameworks to provide a `McpJsonMapper` mapper singleton implementation and feed it to the builders without paying the price of instantiating `McpJsonMappers`, which will not be used. The goal is to be able to use the `ObjectMapper` singleton of an application also for the MCP code.

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>
This commit is contained in:
Graeme Rocher 2025-09-10 12:26:17 +02:00 • committed by Christian Tzolov
commit 80d0ad82a6
1 changed files with 2043 additions and 1421 deletions
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22
mcp/pom.xml
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@ -65,6 +65,11 @@
</build>
<dependencies>
<dependency>
<groupId>io.modelcontextprotocol.sdk</groupId>
<artifactId>mcp-json-jackson2</artifactId>
<version>0.13.0-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
@ -74,7 +79,7 @@
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<artifactId>jackson-annotations</artifactId>
<version>${jackson.version}</version>
</dependency>
@ -83,11 +88,6 @@
<artifactId>reactor-core</artifactId>
</dependency>
<dependency>
<groupId>com.networknt</groupId>
<artifactId>json-schema-validator</artifactId>
<version>${json-schema-validator.version}</version>
</dependency>
<!-- Used by the HttpServletSseServerTransport -->
<dependency>
@ -216,8 +216,14 @@
<scope>test</scope>
</dependency>
<!-- Test-only JSON library for the Gson-based McpJsonMapper example -->
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.10.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
</project>