jaeger-zipkin이 객체의 private 필드에 접근하지 않게 한다.

FixZipkinV2Reporter.kt

import com.google.gson.Gson
import com.google.gson.GsonBuilder
import io.jaegertracing.zipkin.internal.V2SpanConverter
import java.lang.reflect.Field
import java.lang.reflect.Modifier
import java.lang.invoke.MethodHandles
import java.lang.invoke.VarHandle

class FixZipkinV2Reporter(gson: Gson = PRIVACY_RESPECTING_GSON) {
    init {
        //make it accessible
        val field = V2SpanConverter::class.java.getDeclaredField("gson")
        field.isAccessible = true

        //make it modifiable
        try {
            val modifiersField = Field::class.java.getDeclaredField("modifiers")
            modifiersField.isAccessible = true
            modifiersField.setInt(field, field.modifiers and Modifier.FINAL.inv())
        } catch (e: NoSuchFieldException) {
            //Java 12 does not allow access to the fields of java.lang.reflect.Field.
            val accessModifiers: VarHandle = MethodHandles.privateLookupIn(Field::class.java, MethodHandles.lookup())
                .findVarHandle(Field::class.java, "modifiers", Int::class.java)
            accessModifiers.set(field, field.modifiers and Modifier.FINAL.inv())
        }

        //modify
        field.set(null, gson)
    }

    companion object {
        @JvmField
        val PRIVACY_RESPECTING_GSON: Gson = GsonBuilder()
            .excludeFieldsWithModifiers(Modifier.TRANSIENT or Modifier.STATIC or Modifier.PRIVATE)
            .create()
    }
}

FixZipkinV2ReporterTest.kt

import io.jaegertracing.zipkin.internal.V2SpanConverter
import org.junit.jupiter.api.Assertions.assertEquals
import org.junit.jupiter.api.Assertions.assertSame
import org.junit.jupiter.api.Test

class FixZipkinV2ReporterTest {
    private val gson = FixZipkinV2Reporter.PRIVACY_RESPECTING_GSON

    class WithPrivateField(
        @JvmField
        val name: String,
        @JvmField
        private val phoneNumber: String
    )

    @Test
    fun excludePrivateFields() {
        val encoded = gson.toJson(WithPrivateField("john", "282"))
        assertEquals("{\"name\":\"john\"}", encoded)
    }

    @Test
    fun patch() {
        FixZipkinV2Reporter(gson)
        val field = V2SpanConverter::class.java.getDeclaredField("gson")
        field.isAccessible = true
        assertSame(gson, field.get(null))
    }
}