moultingyaml: Scala wrapper for SnakeYAML

Comment¶

If the input YAML doc has multiple formats, you can first load it as an Object and then use Object.isInstanceOf to check its type and use Object.asInstanceOf[SomeType] to cast it to the right type.

In [1]:

%%classpath add mvn
org.yaml snakeyaml 1.25

In [11]:

import scala.collection.JavaConverters._

Out[11]:

import scala.collection.JavaConverters._

In [2]:

import org.yaml.snakeyaml.Yaml

Out[2]:

import org.yaml.snakeyaml.Yaml

In [3]:

import scala.collection.JavaConverters._

Out[3]:

import scala.collection.JavaConverters._

In [4]:

val yaml = new Yaml()

Out[4]:

Yaml:1842984473

In [5]:

val document = "\n- Hesperiidae\n- Papilionidae\n- Apatelodidae\n- Epiplemidae"

Out[5]:

- Hesperiidae
- Papilionidae
- Apatelodidae
- Epiplemidae

In [6]:

val obj = yaml.load(document).asInstanceOf[java.lang.Object]

Out[6]:

[Hesperiidae, Papilionidae, Apatelodidae, Epiplemidae]

In [7]:

obj.isInstanceOf[java.util.List[String]]

Out[7]:

true

In [12]:

obj.isInstanceOf[Seq[String]]

Out[12]:

false

In [9]:

obj.asInstanceOf[java.util.List[String]]

Out[9]:

[Hesperiidae, Papilionidae, Apatelodidae, Epiplemidae]

In [15]:

obj.asInstanceOf[java.util.List[String]]

Out[15]:

[Hesperiidae, Papilionidae, Apatelodidae, Epiplemidae]

In [13]:

obj.asInstanceOf[Seq[String]]

java.lang.ClassCastException: java.util.ArrayList cannot be cast to scala.collection.Seq
  ... 48 elided

In [30]:

val list = yaml.load(document).asInstanceOf[java.util.List[String]]

Out[30]:

[Hesperiidae, Papilionidae, Apatelodidae, Epiplemidae]

In [12]:

list

Out[12]:

[Hesperiidae, Papilionidae, Apatelodidae, Epiplemidae]

In [15]:

val doc = """
    |aa:
    |  - x
    |  - y
    |bb: z
""".stripMargin

Out[15]:

aa:
  - x
  - y
bb: z

In [16]:

yaml.load(doc).asInstanceOf[java.util.Map[String, Any]]

Read YAML From a File¶

The following way of reading from a file is problematic ...

In [21]:

import java.io.{File, FileInputStream}
import org.yaml.snakeyaml.Yaml

val inputStream = new FileInputStream(new File("test.yaml"))
val yaml = new Yaml()

Out[21]:

Yaml:923704732

In [23]:

yaml.load(inputStream).asInstanceOf[java.util.Map[String, Any]]

Cast to Map¶

https://stackoverflow.com/questions/30851141/scala-parse-a-yaml-file-using-snakeyaml

In [36]:

104.62 / 8

Out[36]:

13.0775

In [ ]:

Ben Chuanlong Du's Blog

It is never too late to learn.

Use SnakeYaml in Scala

Comment¶

Read YAML From a File¶

Cast to Map¶

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