feat: typeなどの要素が一つのとき配列ではなく文字列で返すように

src/main/kotlin/dev/usbharu/hideout/ap/JsonLd.kt

@@ -3,15 +3,20 @@ package dev.usbharu.hideout.ap
 import com.fasterxml.jackson.annotation.JsonAutoDetect
 import com.fasterxml.jackson.annotation.JsonCreator
 import com.fasterxml.jackson.annotation.JsonProperty
+import com.fasterxml.jackson.core.JsonGenerator
 import com.fasterxml.jackson.core.TreeNode
 import com.fasterxml.jackson.databind.JsonDeserializer
 import com.fasterxml.jackson.databind.JsonNode
+import com.fasterxml.jackson.databind.JsonSerializer
+import com.fasterxml.jackson.databind.SerializerProvider
 import com.fasterxml.jackson.databind.annotation.JsonDeserialize
+import com.fasterxml.jackson.databind.annotation.JsonSerialize
 
 @JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
 open class JsonLd {
     @JsonProperty("@context")
     @JsonDeserialize(contentUsing = ContextDeserializer::class)
+    @JsonSerialize(using = ContextSerializer::class)
     var context:List<String> = emptyList()
 
     @JsonCreator
@@ -31,3 +36,22 @@ public class ContextDeserializer : JsonDeserializer<String>() {
         return readTree.asText()
     }
 }
+
+public class ContextSerializer : JsonSerializer<List<String>>() {
+    override fun serialize(value: List<String>?, gen: JsonGenerator?, serializers: SerializerProvider?) {
+        if (value.isNullOrEmpty()) {
+            gen?.writeNull()
+            return
+        }
+        if (value?.size == 1) {
+            gen?.writeString(value[0])
+        } else {
+            gen?.writeStartArray()
+            value?.forEach {
+                gen?.writeString(it)
+            }
+            gen?.writeEndArray()
+        }
+    }
+
+}

src/main/kotlin/dev/usbharu/hideout/ap/Object.kt

@@ -1,6 +1,12 @@
 package dev.usbharu.hideout.ap
 
+import com.fasterxml.jackson.core.JsonGenerator
+import com.fasterxml.jackson.databind.JsonSerializer
+import com.fasterxml.jackson.databind.SerializerProvider
+import com.fasterxml.jackson.databind.annotation.JsonSerialize
+
 open class Object : JsonLd {
+    @JsonSerialize(using = TypeSerializer::class)
     private var type: List<String> = emptyList()
     var name: String? = null
 
@@ -19,3 +25,19 @@ open class Object : JsonLd {
         }
     }
 }
+
+public class TypeSerializer : JsonSerializer<List<String>>() {
+    override fun serialize(value: List<String>?, gen: JsonGenerator?, serializers: SerializerProvider?) {
+        println(value)
+        if (value?.size == 1) {
+            gen?.writeString(value[0])
+        } else {
+            gen?.writeStartArray()
+            value?.forEach {
+                gen?.writeString(it)
+            }
+            gen?.writeEndArray()
+        }
+    }
+
+}

src/test/kotlin/dev/usbharu/hideout/ap/ContextSerializerTest.kt

@@ -0,0 +1,23 @@
+package dev.usbharu.hideout.ap
+
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import org.junit.jupiter.api.Assertions.*
+import org.junit.jupiter.api.Test
+
+class ContextSerializerTest{
+
+    @Test
+    fun serialize() {
+        val accept = Accept(
+            name = "aaa",
+            actor = "bbb",
+            `object` = Follow(
+                name = "ccc",
+                `object` = "ddd",
+                actor = "aaa"
+            )
+        )
+        val writeValueAsString = jacksonObjectMapper().writeValueAsString(accept)
+        println(writeValueAsString)
+    }
+}