如何从json字符串中提取值?

问题描述：

我有一个文件，该文件包含一堆列，一个名为jsonstring的列是字符串类型，其中包含json字符串……可以说格式如下:

I have a file which has bunch of columns and one column called jsonstring is of string type which has json strings in it… let's say the format is the following:

{
    "key1": "value1",
    "key2": {
        "level2key1": "level2value1",
        "level2key2": "level2value2"
    }
}

我想将此列解析如下:jsonstring.key1，jsonstring.key2.level2key1返回value1，level2value1

I want to parse this column something like this: jsonstring.key1,jsonstring.key2.level2key1 to return value1, level2value1

我该如何在scala或spark sql中做到这一点.

How can I do that in scala or spark sql.

答

您可以使用withColumn + udf + json4s :

You can use withColumn + udf + json4s:

import org.json4s.{DefaultFormats, MappingException}
import org.json4s.jackson.JsonMethods._
import org.apache.spark.sql.functions._

def getJsonContent(jsonstring: String): (String, String) = {
    implicit val formats = DefaultFormats
    val parsedJson = parse(jsonstring)  
    val value1 = (parsedJson \ "key1").extract[String]
    val level2value1 = (parsedJson \ "key2" \ "level2key1").extract[String]
    (value1, level2value1)
}
val getJsonContentUDF = udf((jsonstring: String) => getJsonContent(jsonstring))

df.withColumn("parsedJson", getJsonContentUDF(df("jsonstring")))

如何从json字符串中提取值?

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