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Lift Framework example source code file (XMLApiHelper.scala)

This example Lift Framework source code file (XMLApiHelper.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

boolean, box, box, empty, empty, failure, full, full, liftresponse, liftresponse, nodeseq, null, text, unprefixedattribute

The Lift Framework XMLApiHelper.scala source code

/*
 * Copyright 2009-2011 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 http
package rest

import net.liftweb.common._
import net.liftweb._
import util._
import Helpers._

import scala.xml.{NodeSeq, Text, Elem, UnprefixedAttribute, Null, Node}

/**
 * Mix this trait into your REST service provider to convert between different
 * response types and a LiftResponse. You need to define the createTag method
 * to provide a root element for your API. You may optionally override the
 * successAttrName, operationAttrName, and/or msgAttrName defs to control the
 * attributes that will be applied to your root element based on the
 * return from your API.
 *
 * For example, the following code implements a simple API that takes a comma-
 * separated string of integers and reduces them with various operations.
 *
<pre name="code" class="scala">
object CalculatorApi extends XmlApiHelper {
  // Define our root tag
  def createTag(contents : NodeSeq) : Elem = <api>{contents}</api>

  // The LiftResponses here will be converted to Box[LiftResponse]
  // via the putResponseInBox implicit conversion
  def calculator : LiftRules.DispatchPF = {
    case r @ Req(List("api","sum"), _, GetRequest) => () => doSum(r)
    case r @ Req(List("api","product"), _, GetRequest) => () => doProduct(r)
    case r @ Req(List("api","max"), _, GetRequest) => () => doMax(r)
    case r @ Req(List("api","min"), _, GetRequest) => () => doMin(r)
    case Req("api" :: _, _, _) => () => BadResponse()
  }

  // Define a common handler
  def reduceOp (operation : (Int,Int) => Int)(r : Req) : Box[Elem] = tryo {
    (r.param("args").map {
      args => <result>{args.split(",").map(_.toInt).reduceLeft(operation)}</result>
     }) ?~ "Missing args"
  } match {
    case Full(x) => x
    case f : Failure => f
    case Empty => Empty
  }

  // Using a return type of LiftResponse causes the canNodeToResponse
  // implicit to be invoked
  def doSum (r : Req) : LiftResponse = reduceOp(_ + _)(r)
  def doProduct (r : Req) : LiftResponse = reduceOp(_ * _)(r)
  def doMax (r : Req) : LiftResponse = reduceOp(_ max _)(r)
  def doMin (r : Req) : LiftResponse = reduceOp(_ min _)(r)
}
</pre>
  *
  * With this API, the URL <pre>http://foo.com/api/sum?args=1,2,3,4,5
would * return <pre name="code" class="xml"> <api operation="sum" success="true"><result>15</result></api> </pre> * */ trait XMLApiHelper { /** * Converts a boolean into a response of a root element with * no contents and the "success" attribute set to the value of * the "in" parameter. */ implicit def boolToResponse(in: Boolean): LiftResponse = buildResponse(in, Empty, <xml:group/>) /** * Converts a boxed boolean into a response of a root element with * no contents and the "success" attribute set to the value of * the "in" parameter. If the Box is a Failure, the "msg" attribute * of the root element will be set to the Failure's msg value. */ implicit def canBoolToResponse(in: Box[Boolean]): LiftResponse = buildResponse(in openOr false, in match { case Failure(msg, _, _) => Full(Text(msg)) case _ => Empty }, <xml:group/>) /** * Converts a boxed Seq[Node] into a response. If the Box is a Full, * the root element uses the contents of the Box as its contents, and * sets the "success" attribute to "true". If the Box is a Failure, * the "success" attribute is set to "false" and the "msg" attribute * is set to the Failure's msg value. If the Box is Empty then the root * element is returned with no contents and the "success" attribute set to * "false". */ implicit def canNodeToResponse(in: Box[Seq[Node]]): LiftResponse = in match { case Full(n) => buildResponse(true, Empty, n) case Failure(msg, _, _) => buildResponse(false, Full(Text(msg)), Text("")) case _ => buildResponse(false, Empty, Text("")) } /** * Converts a Seq[Node] into a root element with the "success" attribute * set to "true" and the Seq[Node] as the contents. */ implicit def listElemToResponse(in: Seq[Node]): LiftResponse = buildResponse(true, Empty, in) /** * Converts a pair of (Boolean,String) into a response of a root * element with no contents, the "success" attribute set to * the value of the first element of the pair, and the "msg" * attribute set to the value of the second element of the pair. */ implicit def pairToResponse(in: (Boolean, String)): LiftResponse = buildResponse(in._1, Full(Text(in._2)), <xml:group/>) /** * Converts a given LiftResponse into a Full[LiftResponse] */ implicit def putResponseInBox(in: LiftResponse): Box[LiftResponse] = Full(in) /** * Determines the value to place in the "operation" attribute of * the root element based on the second element of the request path. */ protected def operation: Option[NodeSeq] = (for (req <- S.request) yield req.path.partPath match { case _ :: name :: _ => name case _ => "" }).map(Text) /** * The method that wraps the outer-most tag around the body. The success, * operation and msg attributes will be merged into the returned Elem. */ def createTag(in: NodeSeq): Elem /** * The name for the success attribute */ def successAttrName = "success" /** * The name for the operation attribue */ def operationAttrName = "operation" /** * The name for the msg attribute */ def msgAttrName = "msg" /** * Build the Response based on Success, an optional message * and the body */ protected def buildResponse(success: Boolean, msg: Box[NodeSeq], body: NodeSeq): LiftResponse = XmlResponse(createTag(body) % (successAttrName -> success) % (new UnprefixedAttribute(operationAttrName, operation, Null)) % (new UnprefixedAttribute(msgAttrName, msg, Null))) }

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