scala lift环境搭建(9)

You are using Lift 1.0's JsCmd, which produces JSON with single-quoted strings and attempting to parse it with scala's parser, which only supports double-quoted strings.

It is important to realize that there are multiple definitions for JSON.

Are single-quoted strings valid in JSON?
They are according to ECMAScript 5th Ed
They are not according to Crockford's original RFC 4627

Lift and Scala provide many ways to parse JSON, sometimes with differing behavior between versions.

The strings accepted by these parsers are not equivalent.


Here are some comments and examples of the various methods to product and parse JSON strings.

Producing JSON with the lift-json library DSL
Recommended
Despite its name, this is a separate project with no dependencies on the rest of Lift

example:scala> import net.liftweb.json.JsonASTimport net.liftweb.json.JsonASTscala> import net.liftweb.json.JsonDSL._import net.liftweb.json.JsonDSL._scala> import net.liftweb.json.Printer._import net.liftweb.json.Printer._scala> val json1 = ("foo" -> 4) ~ ("bar" -> "baz")json1: net.liftweb.json.JsonAST.JObject = JObject(List(JField(foo,JInt(4)), JField(bar,JString(baz))))scala> compact(JsonAST.render(json1))res0: String = {"foo":4,"bar":"baz"}scala> val json2 = List(1,2,3)json2: List[Int] = List(1, 2, 3)scala> compact(JsonAST.render(json2))res1: String = [1,2,3]scala> val json3 = ("foo", 4) ~ ("bar", List(1,2,3))json3: net.liftweb.json.JsonAST.JObject = JObject(List(JField(foo,JInt(4)), JField(bar,JArray(List(JInt(1), JInt(2), JInt(3))))))scala> compact(JsonAST.render(json3))res2: String = {"foo":4,"bar":[1,2,3]}

Parsing JSON with the lift-json library
Recommended
Provides implicit mapping to/from scala case-classes
Case-classes defined in the console are not currently supported (will throw a com.thoughtworks.paranamer.ParameterNamesNotFoundException: Unable to get class bytes)
The example below uses PublicID, a pre-existing scala case-class so that it will work on the scala console.

example:scala> import scala.xml.dtd.PublicIDimport scala.xml.dtd.PublicIDscala> import net.liftweb.json._import net.liftweb.json._scala> import net.liftweb.json.JsonAST._import net.liftweb.json.JsonAST._scala> import net.liftweb.json.JsonDSL._import net.liftweb.json.JsonDSL._scala> implicit val formats = DefaultFormats formats: net.liftweb.json.DefaultFormats.type = net.liftweb.json.DefaultFormats$@7fa27eddscala> val jsonAst = ("publicId1" -> "idString") ~ ("systemId" -> "systemIdStr")jsonAst: net.liftweb.json.JsonAST.JObject = JObject(List(JField(publicId,JString(idString)), JField(systemId,JString(systemIdStr))))scala> jsonAst.extract[PublicID]res0: scala.xml.dtd.PublicID = PUBLIC "idString" "systemIdStr"

Parsing JSON in scala 2.7.7 and 2.8.1
Not Recommended - No longer supported
Scala 2.7.7's parser will not parse single-quoted JSON
This parsing method used in the question

example:scala>import scala.util.parsing.json.JSON._import scala.util.parsing.json.JSON._scala> parseFull("{\"foo\" : 4 }") res1: Option[Any] = Some(Map(foo -> 4.0))scala> parseFull("[ 1,2,3 ]")res2: Option[Any] = Some(List(1.0, 2.0, 3.0))scala> parseFull("{'foo' : 4 }") res3: Option[Any] = None

Parsing JSON in Lift 2.0 and 2.2 with util.JSONParser
Neutral Recommendation
Lift's util.JSONParser will parse single- or double-quoted JSON strings:

example:scala> import net.liftweb.util.JSONParser._import net.liftweb.util.JSONParser._scala> parse("{\"foo\" : 4 }") res1: net.liftweb.common.Box[Any] = Full(Map(foo -> 4.0))scala> parse("[ 1,2,3 ]")res2: net.liftweb.common.Box[Any] = Full(List(1.0, 2.0, 3.0))scala> parse("{'foo' : 4}") res3: net.liftweb.common.Box[Any] = Full(Map(foo -> 4.0))

Parsing JSON in Lift 2.0 and 2.2 with json.JsonParser
Neutral Recommendation
Lift's json.JsonParser will not parse single-quoted JSON strings:

example:scala> import net.liftweb.json._import net.liftweb.json._scala> import net.liftweb.json.JsonParser._import net.liftweb.json.JsonParser._scala> parse("{\"foo\" : 4 }")res1: net.liftweb.json.JsonAST.JValue = JObject(List(JField(foo,JInt(4))))scala> parse("[ 1,2,3 ]")res2: net.liftweb.json.JsonAST.JValue = JArray(List(JInt(1), JInt(2), JInt(3)))scala> parse("{'foo' : 4}") net.liftweb.json.JsonParser$ParseException: unknown token 'Near: {'foo' : 4}at net.liftweb.json.JsonParser$Parser.fail(JsonParser.scala:216)at net.liftweb.json.JsonParser$Parser.nextToken(JsonParser.scala:308)at net.liftweb.json.JsonParser$$anonfun$1.apply(JsonParser.scala:172)at net.liftweb.json.JsonParser$$anonfun$1.apply(JsonParser.scala:129)at net.liftweb.json.JsonParse...

Producing JSON with Lift 1.0 JsCmd
Not Recommended - output not valid for all JSON parsers
Note the single-quotations around strings:

example:scala> import net.liftweb.http.js._import net.liftweb.http.js._scala> import net.liftweb.http.js.JE._import net.liftweb.http.js.JE._scala> JsObj(("foo", 4), ("bar", "baz")).toJsCmdres0: String = {'foo': 4, 'bar': 'baz'}scala> JsArray(1,2,3).toJsCmdres1: String = [1, 2, 3]scala> JsObj(("foo", 4), ("bar", JsArray(1,2,3))).toJsCmdres2: String = {'foo': 4, 'bar': [1, 2, 3]}

Producing JSON with Lift 2.0 JsCmd
Neutral Recommendation
Note the double quotations around strings:

example:scala> import net.liftweb.http.js._import net.liftweb.http.js._scala> import net.liftweb.http.js.JE._import net.liftweb.http.js.JE._scala> JsObj(("foo", 4), ("bar", "baz")).toJsCmdres0: String = {"foo": 4, "bar": "baz"}scala> JsArray(1,2,3).toJsCmdres1: String = [1, 2, 3]scala> JsObj(("foo", 4), ("bar", JsArray(1,2,3))).toJsCmdres3: String = {"foo": 4, "bar": [1, 2, 3]}