Supports snakecase.

src/main/scala/spray/json/SnakeCaseJsonSupport.scala

@@ -0,0 +1,52 @@
+package spray.json
+
+import scala.reflect.ClassTag
+import scala.collection.mutable
+
+/**
+  * Provides snake cased JsonFormats
+  */
+trait SnakeCaseJsonSupport extends DefaultJsonProtocol {
+
+  override protected def extractFieldNames(classTag: ClassTag[_]): Array[String] = {
+    def snakify(name: String) = {
+      val chars = name.toCharArray
+      val len = name.length
+      val sb = new mutable.StringBuilder(len + len / 5)
+
+      def isAlphabetic(char: Char): Boolean = (char >= 'a' && char <= 'z') || (char >= 'A' && char <= 'Z')
+
+      def go(i: Int, rest: Int, processedUpper: Boolean, processedAlphaNumeric: Boolean): String =
+        if (rest == 0) {
+          sb.toString()
+        } else if (rest > 1 && chars(i).isUpper && chars(i + 1).isLower) {
+          if (processedAlphaNumeric) {
+            sb.append('_')
+          }
+          sb.append(chars(i).toLower).append(chars(i + 1))
+          go(i + 2, rest - 2, false, true)
+        } else if (chars(i).isUpper) {
+          if (!processedUpper && processedAlphaNumeric) {
+            sb.append('_')
+          }
+          sb.append(chars(i).toLower)
+          go(i + 1, rest - 1, true, chars(i).isDigit || isAlphabetic(chars(i)))
+        } else if (!isAlphabetic(chars(i))) {
+          sb.append(chars(i))
+          go(i + 1, rest - 1, false, chars(i).isDigit)
+        } else {
+          sb.append(chars(i).toLower)
+          go(i + 1, rest - 1, chars(i).isUpper, chars(i).isDigit || isAlphabetic(chars(i)))
+        }
+
+      go(0, len, true, false)
+    }
+
+    super.extractFieldNames(classTag).map {
+      snakify(_)
+    }
+  }
+
+}
+
+object SnakeCaseJsonSupport extends SnakeCaseJsonSupport

src/test/scala/spray/json/SnakeCaseJsonSupportSpec.scala

@@ -0,0 +1,94 @@
+package spray.json
+
+import java.util.Locale
+
+import org.specs2.mutable._
+
+class SnakeCaseJsonSupportSpec extends Specification with SnakeCaseJsonSupport {
+
+  private val PASS1 = """([A-Z]+)([A-Z][a-z])""".r
+  private val PASS2 = """([a-z\d])([A-Z])""".r
+  private val REPLACEMENT = "$1_$2"
+
+  def snakify(name: String) =
+    PASS2.replaceAllIn(PASS1.replaceAllIn(name, REPLACEMENT), REPLACEMENT).toLowerCase(Locale.US)
+
+  "SnakeCaseJsonSUpport" should {
+    "convert field names to snake cased fields names." in {
+      // Given
+      case class SampleFields(
+          HelloWorld: Int = 0,
+          A1AAbBBBBBbCCcc: Int = 0,
+          AbAAbbAAAbbb1AA2bb1AA2AAAAbb1bAA: Int = 0,
+          x: Int = 0,
+          Y: Int = 0,
+          `^There-arE_Non_(Alphabetic))_character!S`: Int = 0,
+          `tHere-Are_(AlsO)_noN_(alphaBetic))_CharaCter!s`: Int = 0,
+          `  There are space character `: Int = 0,
+          ` これは　マルチバイトAbcのaBc確認です。`: Int = 0,
+          aa: Int = 0,
+          AA: Int = 0,
+          Aa: Int = 0,
+          aA: Int = 0,
+          AAA: Int = 0,
+          AAa: Int = 0,
+          AaA: Int = 0,
+          aAA: Int = 0,
+          aaA: Int = 0,
+          aAa: Int = 0,
+          Aaa: Int = 0,
+          aaa: Int = 0
+      )
+      implicit val jsonFormat: RootJsonFormat[SampleFields] =
+         jsonFormat21(SampleFields.apply)
+      // When
+      val sampleFields = SampleFields().toJson.asJsObject
+      // Then
+      val fields = sampleFields.fields
+      fields.contains(snakify("HelloWorld")) mustEqual true
+      fields.contains(snakify("A1AAbBBBBBbCCcc")) mustEqual true
+      fields.contains(snakify("AbAAbbAAAbbb1AA2bb1AA2AAAAbb1bAA")) mustEqual true
+      fields.contains(snakify("x")) mustEqual true
+      fields.contains(snakify("Y")) mustEqual true
+      fields.contains(snakify("^There-arE_Non_(Alphabetic))_character!S")) mustEqual true
+      fields.contains(snakify("tHere-Are_(AlsO)_noN_(alphaBetic))_CharaCter!s")) mustEqual true
+      fields.contains(snakify("  There are space character ")) mustEqual true
+      fields.contains(snakify(" これは　マルチバイトAbcのaBc確認です。")) mustEqual true
+      fields.contains(snakify("aa")) mustEqual true
+      fields.contains(snakify("aA")) mustEqual true
+      fields.contains(snakify("Aa")) mustEqual true
+      fields.contains(snakify("AA")) mustEqual true
+      fields.contains(snakify("AAA")) mustEqual true
+      fields.contains(snakify("aaA")) mustEqual true
+      fields.contains(snakify("aAa")) mustEqual true
+      fields.contains(snakify("Aaa")) mustEqual true
+      fields.contains(snakify("AAa")) mustEqual true
+      fields.contains(snakify("AaA")) mustEqual true
+      fields.contains(snakify("aAA")) mustEqual true
+      fields.contains(snakify("aaa")) mustEqual true
+    }
+    "deserialize snake cased json" in {
+      // Given
+      case class SampleFields(
+          a: Int,
+          aA: Int,
+          helloWorld: Int,
+          HelloTheWorld: Int
+      )
+      implicit val jsonFormat: RootJsonFormat[SampleFields] =
+        jsonFormat4(SampleFields.apply)
+      val json = JsObject(
+        "hello_the_world" -> 4.toJson,
+        "a_a" -> 2.toJson,
+        "a" -> 1.toJson,
+        "hello_world" -> 3.toJson
+      )
+      // When
+      val result = jsonFormat.read(json)
+      // Then
+      result mustEqual SampleFields(
+        a = 1, aA = 2, helloWorld = 3, HelloTheWorld = 4
+      )
+    }
+  }
+}