使用lift restful 实现资源下载功能

gistfile1.scala

package com.cqccn.iams.server

import java.util.Locale

import org.joda.time.{DateTimeZone, DateTime}
import org.joda.time.format.DateTimeFormat

import net.liftweb.common.Full
import net.liftweb.http.rest.RestHelper
import net.liftweb.http._

object RestDemo extends RestHelper {
  serve {
    case req@Req("api" :: "download" :: "image" :: id :: Nil, suffix, GetRequest) =>
      try
        req.ifModifiedSince match {
          case Full(date) if !MResource.isModified(id, date) => // 数据库中资源未更新
            NotModifiedResponse

          case _ => // 从数据库中获取资源
            val lastModified = DateTime.now
            ImageResponse(Array(), "image/jpeg", 0L, lastModified)
        }
      catch {
        case e: Exception =>
          InternalServerErrorResponse()
      }

  }

  val formatInternetDate =
    DateTimeFormat.forPattern("EEE, d MMM yyyy HH:mm:ss 'GMT'").withLocale(Locale.US).withZone(DateTimeZone.UTC)
}

case class ImageResponse(bytes: Array[Byte], contentType: String, size: Long, lastModified: DateTime) extends LiftResponse {
  val headers =
    List("Content-Type" -> contentType, "Content-Length" -> size.toString, "Last-Modified" -> RestDemo.formatInternetDate.print(lastModified))

  val toResponse =
    InMemoryResponse(bytes, headers, Nil, 200)
}

case object NotModifiedResponse extends LiftResponse with HeaderDefaults {
  val toResponse =
    InMemoryResponse(Array(), headers, cookies, 304)
}