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Lift Framework example source code file (Formats.scala)

This example Lift Framework source code file (Formats.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Lift Framework tags/keywords

a, class, defaultformats, formats, formats, jobject, jvalue, list, list, partialfunction, string, string, typehints, typehints, util

The Lift Framework Formats.scala source code

/*
 * Copyright 2009-2010 WorldWide Conferencing, LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.liftweb
package json

import java.util.{Date, TimeZone}

/** Formats to use when converting JSON.
 * Formats are usually configured by using an implicit parameter:
 * <pre>
 * implicit val formats = net.liftweb.json.DefaultFormats
 * </pre>
 */
trait Formats { self: Formats =>
  val dateFormat: DateFormat
  val typeHints: TypeHints = NoTypeHints
  val customSerializers: List[Serializer[_]] = Nil
  val fieldSerializers: List[(Class[_], FieldSerializer[_])] = Nil

  /**
   * The name of the field in JSON where type hints are added (jsonClass by default)
   */
  val typeHintFieldName = "jsonClass"

  /**
   * Parameter name reading strategy. By deafult 'paranamer' is used.
   */
  val parameterNameReader: ParameterNameReader = Meta.ParanamerReader

  /**
   * Adds the specified type hints to this formats.
   */
  def + (extraHints: TypeHints): Formats = new Formats {
    val dateFormat = Formats.this.dateFormat
    override val typeHintFieldName = self.typeHintFieldName
    override val parameterNameReader = self.parameterNameReader
    override val typeHints = self.typeHints + extraHints
    override val customSerializers = self.customSerializers
    override val fieldSerializers = self.fieldSerializers
  }

  /**
   * Adds the specified custom serializer to this formats.
   */
  def + (newSerializer: Serializer[_]): Formats = new Formats {
    val dateFormat = Formats.this.dateFormat
    override val typeHintFieldName = self.typeHintFieldName
    override val parameterNameReader = self.parameterNameReader
    override val typeHints = self.typeHints
    override val customSerializers = newSerializer :: self.customSerializers
    override val fieldSerializers = self.fieldSerializers
  }

  /**
   * Adds the specified custom serializers to this formats.
   */
  def ++ (newSerializers: Traversable[Serializer[_]]): Formats =
    newSerializers.foldLeft(this)(_ + _)

  /**
   * Adds a field serializer for a given type to this formats.
   */
  def + [A](newSerializer: FieldSerializer[A])(implicit mf: Manifest[A]): Formats = new Formats {
    val dateFormat = Formats.this.dateFormat
    override val typeHintFieldName = self.typeHintFieldName
    override val parameterNameReader = self.parameterNameReader
    override val typeHints = self.typeHints
    override val customSerializers = self.customSerializers
    override val fieldSerializers = (mf.erasure, newSerializer) :: self.fieldSerializers
  }

  private[json] def fieldSerializer(clazz: Class[_]): Option[FieldSerializer[_]] = {
    import ClassDelta._

    val ord = Ordering[Int].on[(Class[_], FieldSerializer[_])](x => delta(x._1, clazz))
    fieldSerializers filter (_._1.isAssignableFrom(clazz)) match {
      case Nil => None
      case xs  => Some((xs min ord)._2)
    }
  }

  def customSerializer(implicit format: Formats) =
    customSerializers.foldLeft(Map(): PartialFunction[Any, JValue]) { (acc, x) =>
      acc.orElse(x.serialize)
    }

  def customDeserializer(implicit format: Formats) =
    customSerializers.foldLeft(Map(): PartialFunction[(TypeInfo, JValue), Any]) { (acc, x) =>
      acc.orElse(x.deserialize)
    }
}

/** Conversions between String and Date.
 */
trait DateFormat {
  def parse(s: String): Option[Date]
  def format(d: Date): String
}

trait Serializer[A] {
  def deserialize(implicit format: Formats): PartialFunction[(TypeInfo, JValue), A]
  def serialize(implicit format: Formats): PartialFunction[Any, JValue]
}

/** Type hints can be used to alter the default conversion rules when converting
 * Scala instances into JSON and vice versa. Type hints must be used when converting
 * class which is not supported by default (for instance when class is not a case class).
 * <p>
 * Example:<pre>
 * class DateTime(val time: Long)
 *
 * val hints = new ShortTypeHints(classOf[DateTime] :: Nil) {
 *   override def serialize: PartialFunction[Any, JObject] = {
 *     case t: DateTime => JObject(JField("t", JInt(t.time)) :: Nil)
 *   }
 *
 *   override def deserialize: PartialFunction[(String, JObject), Any] = {
 *     case ("DateTime", JObject(JField("t", JInt(t)) :: Nil)) => new DateTime(t.longValue)
 *   }
 * }
 * implicit val formats = DefaultFormats.withHints(hints)
 * </pre>
 */
trait TypeHints {
  import ClassDelta._

  val hints: List[Class[_]]

  /** Return hint for given type.
   */
  def hintFor(clazz: Class[_]): String

  /** Return type for given hint.
   */
  def classFor(hint: String): Option[Class[_]]

  def containsHint_?(clazz: Class[_]) = hints exists (_ isAssignableFrom clazz)
  def deserialize: PartialFunction[(String, JObject), Any] = Map()
  def serialize: PartialFunction[Any, JObject] = Map()

  def components: List[TypeHints] = List(this)

  /**
   * Adds the specified type hints to this type hints.
   */
  def + (hints: TypeHints): TypeHints = CompositeTypeHints(hints.components ::: components)

  private[TypeHints] case class CompositeTypeHints(override val components: List[TypeHints]) extends TypeHints {
    val hints: List[Class[_]] = components.flatMap(_.hints)

    /**
     * Chooses most specific class.
     */
    def hintFor(clazz: Class[_]): String = components.filter(_.containsHint_?(clazz))
      .map(th => (th.hintFor(clazz), th.classFor(th.hintFor(clazz)).getOrElse(error("hintFor/classFor not invertible for " + th))))
      .sort((x, y) => delta(x._2, clazz) - delta(y._2, clazz) < 0).head._1

    def classFor(hint: String): Option[Class[_]] = {
      def hasClass(h: TypeHints) =
        scala.util.control.Exception.allCatch opt (h.classFor(hint)) map (_.isDefined) getOrElse(false)

      components find (hasClass) flatMap (_.classFor(hint))
  }

    override def deserialize: PartialFunction[(String, JObject), Any] = components.foldLeft[PartialFunction[(String, JObject),Any]](Map()) {
      (result, cur) => result.orElse(cur.deserialize)
    }

    override def serialize: PartialFunction[Any, JObject] = components.foldLeft[PartialFunction[Any, JObject]](Map()) {
      (result, cur) => result.orElse(cur.serialize)
    }
  }
}

private[json] object ClassDelta {
  def delta(class1: Class[_], class2: Class[_]): Int = {
    if (class1 == class2) 0
    else if (class1.getInterfaces.contains(class2)) 0
    else if (class2.getInterfaces.contains(class1)) 0
    else if (class1.isAssignableFrom(class2)) {
      1 + delta(class1, class2.getSuperclass)
    }
    else if (class2.isAssignableFrom(class1)) {
      1 + delta(class1.getSuperclass, class2)
    }
    else error("Don't call delta unless one class is assignable from the other")
  }
}

/** Do not use any type hints.
 */
case object NoTypeHints extends TypeHints {
  val hints = Nil
  def hintFor(clazz: Class[_]) = error("NoTypeHints does not provide any type hints.")
  def classFor(hint: String) = None
}

/** Use short class name as a type hint.
 */
case class ShortTypeHints(hints: List[Class[_]]) extends TypeHints {
  def hintFor(clazz: Class[_]) = clazz.getName.substring(clazz.getName.lastIndexOf(".")+1)
  def classFor(hint: String) = hints find (hintFor(_) == hint)
}

/** Use full class name as a type hint.
 */
case class FullTypeHints(hints: List[Class[_]]) extends TypeHints {
  def hintFor(clazz: Class[_]) = clazz.getName
  def classFor(hint: String) = Some(Thread.currentThread.getContextClassLoader.loadClass(hint))
}

/** Default date format is UTC time.
 */
object DefaultFormats extends DefaultFormats {
  val losslessDate = new ThreadLocal(new java.text.SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"))
  val UTC = TimeZone.getTimeZone("UTC")
}

trait DefaultFormats extends Formats {
  import java.text.{ParseException, SimpleDateFormat}

  val dateFormat = new DateFormat {
    def parse(s: String) = try {
      Some(formatter.parse(s))
    } catch {
      case e: ParseException => None
    }

    def format(d: Date) = formatter.format(d)

    private def formatter = {
      val f = dateFormatter
      f.setTimeZone(DefaultFormats.UTC)
      f
    }
  }

  protected def dateFormatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'")

  /** Lossless date format includes milliseconds too.
   */
  def lossless = new DefaultFormats {
    override def dateFormatter = DefaultFormats.losslessDate()
  }

  /** Default formats with given <code>TypeHints.
   */
  def withHints(hints: TypeHints) = new DefaultFormats {
    override val typeHints = hints
  }
}

private[json] class ThreadLocal[A](init: => A) extends java.lang.ThreadLocal[A] with (() => A) {
  override def initialValue = init
  def apply = get
}

Other Lift Framework examples (source code examples)

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