Here's a failing test that reproduces the issue

package com.example.demo;

import org.junit.jupiter.api.Test;
import tools.jackson.core.JsonGenerator;
import tools.jackson.databind.json.JsonMapper;

import java.io.StringWriter;
import java.util.UUID;

public class JacksonTests {

    @Test
    void jacksonUUIDSerialization() {
        JsonMapper mapper = new JsonMapper();
        JsonGenerator generator = mapper.createGenerator(new StringWriter());
        generator.writeStartObject();
        generator.writePOJOProperty("id", UUID.randomUUID());
        generator.writeEndObject();
    }
}

The failure stacktrace is below

Cannot invoke "tools.jackson.core.util.JacksonFeatureSet.isEnabled(tools.jackson.core.util.JacksonFeature)" because "this._writeCapabilities" is null
java.lang.NullPointerException: Cannot invoke "tools.jackson.core.util.JacksonFeatureSet.isEnabled(tools.jackson.core.util.JacksonFeature)" because "this._writeCapabilities" is null
    at tools.jackson.databind.SerializationContext.isEnabled(SerializationContext.java:495)
    at tools.jackson.databind.ser.jdk.UUIDSerializer._writeAsBinary(UUIDSerializer.java:116)
    at tools.jackson.databind.ser.jdk.UUIDSerializer.serialize(UUIDSerializer.java:78)
    at tools.jackson.databind.ser.jdk.UUIDSerializer.serialize(UUIDSerializer.java:23)
    at tools.jackson.databind.SerializationContext.writeValue(SerializationContext.java:308)
    at tools.jackson.core.base.GeneratorBase.writePOJO(GeneratorBase.java:298)
    at tools.jackson.core.JsonGenerator.writePOJOProperty(JsonGenerator.java:1850)
    at com.example.demo.JacksonTests.jacksonUUIDSerialization(JacksonTests.java:17)

Comment From: cowtowncoder

Thank you for reporting this, @donalmurtagh.

I think this belongs to jackson-databind (altho exception from jackson-core), will transfer.

Comment From: cowtowncoder

Note: could be related to earlier issue #5225 (fixed via #5226)

Comment From: cowtowncoder

Fixed via #5324