diff --git a/scalabot-meta/src/main/kotlin/serializer/Serializer.kt b/scalabot-meta/src/main/kotlin/serializer/Serializer.kt
index 9899b96..9b55257 100644
--- a/scalabot-meta/src/main/kotlin/serializer/Serializer.kt
+++ b/scalabot-meta/src/main/kotlin/serializer/Serializer.kt
@@ -3,6 +3,7 @@ package net.lamgc.scalabot.config.serializer
 import com.google.gson.*
 import com.google.gson.reflect.TypeToken
 import net.lamgc.scalabot.config.*
+import net.lamgc.scalabot.config.serializer.SerializeUtils.getPrimitiveValueOrThrow
 import org.eclipse.aether.artifact.AbstractArtifact
 import org.eclipse.aether.artifact.Artifact
 import org.eclipse.aether.artifact.DefaultArtifact
@@ -81,8 +82,8 @@ object AuthenticationSerializer : JsonDeserializer<Authentication> {
         if (json !is JsonObject) {
             throw JsonParseException("Unsupported JSON type.")
         }
-        val username = SerializerUtils.checkJsonKey(json, "username")
-        val password = SerializerUtils.checkJsonKey(json, "password")
+        val username = json.getPrimitiveValueOrThrow("username").asString
+        val password = json.getPrimitiveValueOrThrow("password").asString
         val builder = AuthenticationBuilder()
         builder.addUsername(username)
         builder.addPassword(password)
@@ -91,14 +92,14 @@ object AuthenticationSerializer : JsonDeserializer<Authentication> {
 
 }
 
-private object SerializerUtils {
-    fun checkJsonKey(json: JsonObject, key: String): String {
-        if (!json.has(key)) {
-            throw JsonParseException("Required field does not exist: $key")
-        } else if (!json.get(key).isJsonPrimitive) {
-            throw JsonParseException("Wrong field `$key` type: ${json.get(key)::class.java}")
+internal object SerializeUtils {
+
+    fun JsonObject.getPrimitiveValueOrThrow(fieldName: String): JsonPrimitive {
+        val value = get(fieldName) ?: throw JsonParseException("Missing `$fieldName` field.")
+        if (value !is JsonPrimitive) {
+            throw JsonParseException("Invalid `account` field type.")
         }
-        return json.get(key).asString
+        return value
     }
 }
 
@@ -114,7 +115,7 @@ object MavenRepositoryConfigSerializer
             is JsonObject -> {
                 MavenRepositoryConfig(
                     id = json.get("id")?.asString,
-                    url = URL(SerializerUtils.checkJsonKey(json, "url")),
+                    url = URL(json.getPrimitiveValueOrThrow("url").asString),
                     proxy = if (json.has("proxy"))
                         context.deserialize<Proxy>(
                             json.get("proxy"), Proxy::class.java
diff --git a/scalabot-meta/src/test/kotlin/serializer/SerializersKtTest.kt b/scalabot-meta/src/test/kotlin/serializer/SerializeUtilsTest.kt
similarity index 95%
rename from scalabot-meta/src/test/kotlin/serializer/SerializersKtTest.kt
rename to scalabot-meta/src/test/kotlin/serializer/SerializeUtilsTest.kt
index c5cd5dd..6029775 100644
--- a/scalabot-meta/src/test/kotlin/serializer/SerializersKtTest.kt
+++ b/scalabot-meta/src/test/kotlin/serializer/SerializeUtilsTest.kt
@@ -5,6 +5,7 @@ import io.mockk.every
 import io.mockk.mockk
 import io.mockk.verify
 import net.lamgc.scalabot.config.*
+import net.lamgc.scalabot.config.serializer.SerializeUtils.getPrimitiveValueOrThrow
 import org.eclipse.aether.artifact.Artifact
 import org.eclipse.aether.artifact.DefaultArtifact
 import org.eclipse.aether.repository.Authentication
@@ -12,54 +13,39 @@ import org.eclipse.aether.repository.AuthenticationContext
 import org.eclipse.aether.repository.Proxy
 import org.intellij.lang.annotations.Language
 import org.junit.jupiter.api.Assertions.assertThrows
-import java.lang.reflect.InvocationTargetException
-import java.lang.reflect.Method
 import java.lang.reflect.Type
 import java.net.URL
 import kotlin.test.*
 
-internal class SerializersKtTest {
-
-    private val instance: Any
-    private val method: Method
-
-    init {
-        val clazz = Class.forName("net.lamgc.scalabot.config.serializer.SerializerUtils")
-        method = clazz.getDeclaredMethod("checkJsonKey", JsonObject::class.java, String::class.java)
-        method.isAccessible = true
-        instance = clazz.getDeclaredField("INSTANCE").apply {
-            isAccessible = true
-        }.get(null)
-    }
-
-    private fun invoke(json: JsonObject, key: String): String {
-        try {
-            return method.invoke(instance, json, key) as String
-        } catch (e: InvocationTargetException) {
-            throw e.targetException
-        }
-    }
+internal class SerializeUtilsTest {
 
     @Test
-    fun `Json key checker test`() {
+    fun `getPrimitiveValueOrThrow test`() {
         assertThrows(JsonParseException::class.java) {
-            invoke(JsonObject(), "NOT_EXIST_KEY")
-        }
-        assertThrows(JsonParseException::class.java) {
-            invoke(JsonObject().apply { add("NULL_KEY", JsonNull.INSTANCE) }, "NULL_KEY")
-        }
-        assertThrows(JsonParseException::class.java) {
-            invoke(JsonObject().apply { add("ARRAY_KEY", JsonArray()) }, "ARRAY_KEY")
-        }
-        assertThrows(JsonParseException::class.java) {
-            invoke(JsonObject().apply { add("OBJECT_KEY", JsonObject()) }, "OBJECT_KEY")
+            JsonObject().getPrimitiveValueOrThrow("NOT_EXIST_KEY")
         }
 
-        val expectKey = "TEST"
-        val expectString = "testString"
-        val json = JsonObject().apply { addProperty(expectKey, expectString) }
+        assertThrows(JsonParseException::class.java) {
+            JsonObject().apply {
+                add("testKey", JsonArray())
+            }.getPrimitiveValueOrThrow("testKey")
+        }
+        assertThrows(JsonParseException::class.java) {
+            JsonObject().apply {
+                add("testKey", JsonObject())
+            }.getPrimitiveValueOrThrow("testKey")
+        }
+        assertThrows(JsonParseException::class.java) {
+            JsonObject().apply {
+                add("testKey", JsonNull.INSTANCE)
+            }.getPrimitiveValueOrThrow("testKey")
+        }
 
-        assertEquals(expectString, invoke(json, expectKey))
+        val expectKey = "STRING_KEY"
+        val expectValue = JsonPrimitive("A STRING")
+        assertEquals(expectValue, JsonObject()
+            .apply { add(expectKey, expectValue) }
+            .getPrimitiveValueOrThrow(expectKey))
     }
 }