Add JsonPointer property deserialization support

[arnabnandy7]

Summary

Adds databind support for deserializing POJO properties from nested JSON values selected with @JsonPointer.

References:

• Annotation API: Add JsonPointer annotation for nested binding jackson-annotations#358
• Original feature request: Support binding POJO properties usnig JSON binder jackson-annotations#357

Example

Given:

{
  "name": "Bob",
  "employee": {
    "details": {
      "departmentId": 123
    }
  }
}

A property can be bound directly using:

public class Employee {
    public String name;

    @JsonPointer("/employee/details/departmentId")
    public Integer departmentId;
}

Implementation

• Adds @JsonPointer support to AnnotationIntrospector.
• Supports annotation-introspector pairs and JacksonAnnotationIntrospector.
• Detects and contextualizes pointer-bound properties during bean deserializer resolution.
• Buffers input only for POJOs containing pointer-bound properties.
• Uses the existing property deserializer when binding the selected value, preserving standard type coercion, custom deserializers, null handling, and assignment behavior.
• Removes pointer-only top-level source properties from regular bean binding so they are not treated as unknown.
• Continues to report unrelated unknown properties when FAIL_ON_UNKNOWN_PROPERTIES is enabled.

Initial scope

• Deserialization only.
• Supports fields and setter methods.
• Creator properties are explicitly rejected.
• A missing pointer target leaves the property unchanged.
• An explicit JSON null uses normal property null handling.
• Pointer syntax and escaping follow RFC 6901.

Testing

Focused coverage includes:

• Nested field binding
• Setter binding
• RFC 6901 escaping
• Missing pointer targets
• Explicit JSON null
• Unrelated unknown-property handling

./mvnw -Dtest=JsonPointerDeserializationTest test

Result:

Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

[gitar-bot]

CI failed: Build failure across all jobs caused by a missing import for `JsonPointer` in `JacksonAnnotationIntrospector.java`.

Overview

A consistent build failure occurred across all 4 analyzed CI jobs due to a missing symbol JsonPointer in JacksonAnnotationIntrospector.java during compilation.

Failures

Missing symbol JsonPointer in JacksonAnnotationIntrospector (confidence: high)

• Type: build
• Affected jobs: 94200817166, 94200817006, 94200817022, 94200816984
• Related to change: yes
• Root cause: JacksonAnnotationIntrospector.java references JsonPointer at line 523, but the required import statement is missing from the file.
• Suggested fix: Add the appropriate import statement for JsonPointer (e.g., import tools.jackson.core.JsonPointer; or equivalent) in src/main/java/tools/jackson/databind/introspect/JacksonAnnotationIntrospector.java.

Summary

• Change-related failures: 4 build failures caused by a missing import/class reference in JacksonAnnotationIntrospector.java.
• Infrastructure/flaky failures: 0
• Recommended action: Add the missing JsonPointer import in JacksonAnnotationIntrospector.java and re-run the build.

Code Review ✅ Approved 4 resolved / 4 findings

Adds @JsonPointer property deserialization support using buffered input and RFC 6901 compliant parsing, addressing findings related to update paths, deep copy overhead, invalid pointer expressions, and error wrapping.

✅ 4 resolved

✅ Edge Case: JsonPointer ignored on update/merge deserialization path

📄 src/main/java/tools/jackson/databind/deser/bean/BeanDeserializer.java:187-201 📄 src/main/java/tools/jackson/databind/deser/bean/BeanDeserializer.java:266-280 📄 src/main/java/tools/jackson/databind/deser/bean/BeanDeserializerBase.java:607-620
Pointer handling is only wired into deserialize(JsonParser, DeserializationContext). The update path deserialize(p, ctxt, bean) (used by readerForUpdating(...) and property @JsonMerge/POJO-into-existing binding) never invokes _jsonPointerPropertyHandler, and because the property was removed from _beanProperties in resolve(), it is also not bound there. Result: pointer-bound properties are silently skipped when updating an existing instance. Either route the update path through the pointer handler as well, or document/reject the update case explicitly so the omission is not silent.

✅ Performance: Full deepCopy of source tree on every pointer-bean deserialization

📄 src/main/java/tools/jackson/databind/deser/impl/JsonPointerPropertyHandler.java:50-52 📄 src/main/java/tools/jackson/databind/deser/bean/BeanDeserializer.java:190-201
For any POJO containing a pointer property, each deserialization now reads the entire input into a tree (readTree), performs a full deepCopy() of the root ObjectNode, then re-parses via TreeTraversingParser — roughly tripling work and doubling peak memory. The deepCopy() clones all nested subtrees only to drop a few top-level keys. Since nodes are effectively immutable during read, a shallow copy (new ObjectNode sharing existing child references, minus the pointer roots) is sufficient and much cheaper.

✅ Quality: Invalid @JsonPointer expression throws raw IllegalArgumentException

📄 src/main/java/tools/jackson/databind/deser/impl/JsonPointerPropertyHandler.java:28-30 📄 src/main/java/tools/jackson/databind/deser/bean/BeanDeserializerBase.java:607-618
addProperty calls JsonPointer.compile(expression) during resolve(), which throws IllegalArgumentException for malformed input (e.g. a value not starting with '/'). This surfaces as a raw, low-context exception during deserializer construction instead of a proper InvalidDefinitionException. Validate/compile the expression where DeserializationContext is available and route failures through ctxt.reportBadDefinition(...) for a clear, bean-scoped error message.

✅ Quality: process() does not wrap property errors with wrapAndThrow

📄 src/main/java/tools/jackson/databind/deser/impl/JsonPointerPropertyHandler.java:55-67
In JsonPointerPropertyHandler.process, deserializeAndSet is invoked directly, so any failure propagates without the bean/property context that BeanDeserializer normally adds via wrapAndThrow. Errors on pointer-bound properties will therefore have less actionable diagnostics (no property path / bean reference) than errors on normal properties. Consider wrapping the call in a try/catch that produces an equivalent contextualized exception.

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[arnabnandy7]

It depends on FasterXML/jackson-annotations#358 until that's merged and the updated 2.23-SNAPSHOT becomes available to CI it'll keep on failing.