java - 使用 Apache Spark 读取 Json 文件

Question

我正在尝试使用 Spark v2.0.0 读取 Json 文件。在简单数据代码的情况下效果非常好。如果数据有点复杂，当我打印 df.show() 时，数据没有以正确的方式显示。

这是我的代码:

SparkSession session = SparkSession.builder().master("local").appName("jsonreader").getOrCreate();
Dataset<Row> list = session.read().json("/Users/hadoop/Desktop/sample.json");
list.show();

这是我的示例数据:

{
    "glossary": {
        "title": "example glossary",
        "GlossDiv": {
            "title": "S",
            "GlossList": {
                "GlossEntry": {
                    "ID": "SGML",
                    "SortAs": "SGML",
                    "GlossTerm": "Standard Generalized Markup Language",
                    "Acronym": "SGML",
                    "Abbrev": "ISO 8879:1986",
                    "GlossDef": {
                        "para": "A meta-markup language, used to create markup languages such as DocBook.",
                        "GlossSeeAlso": ["GML", "XML"]
                    },
                    "GlossSee": "markup"
                }
            }
        }
    }
}

我的输出是这样的:

+--------------------+
|     _corrupt_record|
+--------------------+
|                   {|
|       "glossary": {|
|        "title": ...|
|           "GlossDiv": {|
|            "titl...|
|               "GlossList": {|
|                "...|
|                 ...|
|                   "SortAs": "S...|
|                   "GlossTerm":...|
|                   "Acronym": "...|
|                   "Abbrev": "I...|
|                   "GlossDef": {|
|                 ...|
|                       "GlossSeeAl...|
|                 ...|
|                   "GlossSee": ...|
|                   }|
|                   }|
|                   }|
+--------------------+
only showing top 20 rows

Answer 1

如果您必须阅读此 JSON，则需要将 JSON 格式化为一行。这是一个多行 JSON，因此没有被正确读取和加载 (One Object one Row)

引用 JSON API:

Loads a JSON file (one object per line) and returns the result as a DataFrame.

{"glossary":{"title":"example glossary","GlossDiv":{"title":"S","GlossList":{"GlossEntry":{"ID":"SGML","SortAs":"SGML","GlossTerm":"Standard Generalized Markup Language","Acronym":"SGML","Abbrev":"ISO 8879:1986","GlossDef":{"para":"A meta-markup language, used to create markup languages such as DocBook.","GlossSeeAlso":["GML","XML"]},"GlossSee":"markup"}}}}}

我只是在 shell 上试​​了一下，它应该以同样的方式从代码中工作(当我读取多行 JSON 时，我遇到了同样的损坏记录错误)

scala> val df = spark.read.json("C:/DevelopmentTools/data.json")
df: org.apache.spark.sql.DataFrame = [glossary: struct<GlossDiv: struct<GlossList: struct<GlossEntry: struct<Abbrev: string, Acronym: string ... 5 more fields>>, title: string>, title: string>]

scala>

编辑:

例如，您可以使用任何操作从该数据框中获取值

scala> df.select(df("glossary.GlossDiv.GlossList.GlossEntry.GlossTerm")).show()
+--------------------+
|           GlossTerm|
+--------------------+
|Standard Generali...|
+--------------------+


scala>

你也应该能够从你的代码中做到这一点