Scala Json Lift - 一个记录的映射异常错误

Question

我在解析 json 时遇到问题。仅当有一组记录时，无论所有列都具有值还是具有一个或多个列空值，都会出现此问题。其他情况它工作正常。

我的输入案例类如下：

case class Source(AccountNo: String, Name: String)
case class HitsIndex(_index: String, _type: String, _id: String, _score: Double, _source: Source)
case class HitsCount(total: Int, max_score: Double, hits: List[HitsIndex])
case class Shards(total: Int, successful: Int, failed: Int, hits: HitsCount)
case class ParseJson(took: Int, timed_out: Boolean, _shards: Shards)

导入语句：

import scala.collection.mutable._
import net.liftweb.json._
import net.liftweb.json.DefaultFormats
import net.liftweb.json.Serialization.write

以下是我测试的代码：

case class Uiresult(AccountNo: String, Name: String)
val json = parse(jsonString)
val elements = (json \ "_source").children
for (acct <- elements) {
val m = acct.extract[Source]
val res = write(Uiresult(m.accountNo,  (m.firstName.toString() + m.lastName.toString()))
println(res)
}

一条记录的所需输出：

注意：姓氏为空

[
{"AccountNo":"1234","Name":"Augustin "}
]

注意：所有列都有值

[
{"AccountNo":"1234","Name":"Augustin Wagstuff "}
]

但是收到如下错误消息：

> Exception in thread "main" net.liftweb.json.MappingException: No usable value for AccountNo
Did not find value which can be converted into java.lang.String
at net.liftweb.json.Meta$.fail(Meta.scala:191)
at net.liftweb.json.Extraction$.mkValue$1(Extraction.scala:357)
at net.liftweb.json.Extraction$.net$liftweb$json$Extraction$$build$1(Extraction.scala:317)
at net.liftweb.json.Extraction$$anonfun$14.apply(Extraction.scala:253)
at net.liftweb.json.Extraction$$anonfun$14.apply(Extraction.scala:253)
at scala.collection.immutable.List.map(List.scala:273)
at net.liftweb.json.Extraction$.instantiate$1(Extraction.scala:253)
at net.liftweb.json.Extraction$.newInstance$1(Extraction.scala:286)
at net.liftweb.json.Extraction$.net$liftweb$json$Extraction$$build$1(Extraction.scala:315)
at net.liftweb.json.Extraction$.net$liftweb$json$Extraction$$extract0(Extraction.scala:366)
at net.liftweb.json.Extraction$.net$liftweb$json$Extraction$$extract0(Extraction.scala:199)
at net.liftweb.json.Extraction$.extract(Extraction.scala:43)
at net.liftweb.json.JsonAST$JValue.extract(JsonAST.scala:312)
at com.aexp.prospect.atul.sample_01.JsonRead$$anonfun$1.apply(JsonRead.scala:115)
at com.aexp.prospect.atul.sample_01.JsonRead$$anonfun$1.apply(JsonRead.scala:114)
at scala.collection.immutable.List.map(List.scala:273)
at com.aexp.prospect.atul.sample_01.JsonRead$.main(JsonRead.scala:114)
at com.aexp.prospect.atul.sample_01.JsonRead.main(JsonRead.scala)
Caused by: net.liftweb.json.MappingException: Did not find value which can be converted into java.lang.String
at net.liftweb.json.Meta$.fail(Meta.scala:191)
at net.liftweb.json.Extraction$.convert(Extraction.scala:403)
at net.liftweb.json.Extraction$.net$liftweb$json$Extraction$$build$1(Extraction.scala:314)
at net.liftweb.json.Extraction$.mkValue$1(Extraction.scala:351)
... 16 more

我的输入 Json：(姓氏为空)

注意：所有列都有值

{
"took": 1,
"timed_out": false,
"_shards": {
"total": 3,
"successful": 3,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 2.2488084,
"hits": [
{
"_index": "test_02",
"_type": "test_type",
"_id": "123456",
"_score": 2.2488084,
"_source": {
"AccountNo": "06009625297",
"firstName": "Augustin",
"lastName": "Wagstuff "
}
}
]
}
}   

注意：姓氏为空

{
"took": 1,
"timed_out": false,
"_shards": {
"total": 3,
"successful": 3,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 2.2488084,
"hits": [
{
"_index": "test_02",
"_type": "test_type",
"_id": "123456",
"_score": 2.2488084,
"_source": {
"AccountNo": "06009625297",
"firstName": "Augustin",
"lastName": ""
}
}
]
}
}   

Json 对象打印：

示例1：
在这里我注意到所有列都有值。我只选择了一组记录，这是一个问题。

json JObject(List(JField(took，JInt(1))，JField(timed_out，JBool(false))，JField(_shards，JObject(List(JField(total，JInt(3))，JField(success，JInt(3))， JField(failed，JInt(0))))， JField(hits，JObject(List(JField(total，JInt(1))， JField(max_score，JDouble(2.2488084))， JField(hits，JArray(List(JObject(List(JField(_index，JString(test_02))， JField(_type，JString(test_type))， JField(_id，JString(123456))， JField(_score，JDouble(2.2488084))， JField(_source，JObject(List(JField(AccountNo，JString(06009625297))， JField(firstName，JString(Augustin))， JField(lastName，JString(

))))))例 ： 2 在这里，我注意到这里的姓氏是空的。我只选择了一组记录，这是一个问题。有人可以帮我如何处理这个案子吗？

json JObject(List(JField(took，JInt(1))，JField(timed_out，JBool(false))，JField(_shards，JObject(List(JField(total，JInt(3))，JField(success，JInt(3))， JField(failed，JInt(0))))， JField(hits，JObject(List(JField(total，JInt(1))， JField(max_score，JDouble(2.2488084))， JField(hits，JArray(List(JObject(List(JField(_index，JString(test_02))， JField(_type，JString(test_type))， JField(_id，JString(123456))， JField(_score，JDouble(2.2488084))， JField(_source，JObject(List(JField(AccountNo，JString(06009625297))， JField(firstName，JString(Augustin))， JField(lastName，JString(

))))))输入中有 2 组或更多组记录的示例：

输入有 2 组记录(仅提取 2 而不是 1)：这不会产生任何问题并产生所需的输出。如果您注意到第一个记录与前面的示例相同：2 个输入，但在这里它不会产生任何错误。

{
"took": 1,
"timed_out": false,
"_shards": {
"total": 3,
"successful": 3,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 2.2488084,
"hits": [
{
"_index": "test_02",
"_type": "test_type",
"_id": "123456",
"_score": 2.2488084,
"_source": {
"AccountNo": "06009625297",
"firstName": "Augustin",
"lastName": "Wagstuff"
},
"hits": [
{
"_index": "test_02",
"_type": "test_type",
"_id": "789078",
"_score": 2.2188084,
"_source": {
"AccountNo": "06009625297",
"firstName": "Augustin",
"lastName": "Jhonson"
}
}
]
}
}

输出：它按预期到来。

[
{"AccountNo":"06009625297","Name":"Augustin Wagstuff "},
{"AccountNo":"06009625297","Name":"Augustin Jhonson"},
]

代码中的帐户值：

当我尝试在 acct 中显示竞争(引用代码中的变量)时，当输出中有一组记录时，即使输入中的所有其他列都有有效值，我也只能看到第一列。

acct JField(AccountNo,JString(1234))

当我尝试在 acct 中显示争用(引用代码中的变量)时，当输出中有两组记录时，即使所有列都有有效值，我也只能看到第一列。

acct JField(_source，JObject(List(JField(AccountNo，JString(06009625297))， JField(firstName，JString(Augustin))， JField(lastName，JString(Wagstuff

))))) acct JField(_source，JObject(List(JField(AccountNo，JString(06009625297))， JField(firstName，JString(Augustin))， JField(lastName，JString(Jhonson)

))))当我迭代列表时，我怀疑这个问题。请有人帮我解决。

Answer 1

我创建了一个代码来处理有 1 条或零条输入记录的情况。 2 条或更多记录正在工作(感谢 Shaido)。下面是代码，有人可以建议，是否可以以更好的方式构建此代码。

case class Source(AccountNo: fnameString, : String, lname: String)
case class HitsIndex(_index: String, _type: String, _id: String, _score: Double, _source: Source)
case class HitsCount(total: Int, max_score: Double, hits: List[HitsIndex])
case class Shards(total: Int, successful: Int, failed: Int)
case class ParseJson(took: Int, timed_out: Boolean, _shards: Shards, hits: HitsCount)
case class Uiresult(masterid: String, value: String)
case class ErrorMsg(searchType: String, error_message: String)
def formatResult(jsonString: String, searchType: String): String = {
implicit val formats = DefaultFormats
val json = JsonParser.parse(jsonString)
val elements = (json \ "_source").children
if (elements.isEmpty == true) {
implicit val formats = DefaultFormats
return (List(write(ErrorMsg(searchType, "No Matching Record Found"))).mkString("[n", ",n", "n]"))
}
if (json.extract[ParseJson].hits.total == 1) {
val m = (json \ "_source").extract[Source]
val list = List(write(Uiresult(m.AccountNo.toString(), (m.fname.toString() + m.lname.toString() ))))
return (list.mkString("[n", ",n", "n]"))
} else {
val elements = (json \ "_source").children
val list = for (source <- elements) yield {
println(" source " + source)
val m = source.extract[Source]
val list = List(write(Uiresult(m.AccountNo.toString(), (m.fname.toString() + m.lname.toString() ))))
}
return (list.mkString("[n", ",n", "n]"))
}
}

Answer 2

在 Parse json 中使用 scala 中的 liftweb 时也发生了类似的讨论，但没有可用的值

当我使用 lift-json_2.11 版本作为 3.2.0 时，我也遇到了这个问题经过多次试验，最终我使用 2.6.3 版解决了这个问题

<dependency>
<groupId>net.liftweb</groupId>
<artifactId>lift-json_2.11</artifactId>
<version>2.6.3</version>
</dependency>