How do I parse a YAML file in groovy?

Question

say if you have a file called example.yaml which contains the following: - subject: maths .

How do i grab the string after - subject ?

I already can read the contents of the file but want to know how to grab a specific string from it.

note: i know regex may help but have never used it and would appreciate any help.

Answer 1

UPDATE (2020)

Groovy 3 now includes a groovy.yaml.YamlSlurper (similar to JsonSlurper / XmlSlurper )

For previous versions (Original answer) :

snakeyaml is a library to parse YAML files. Easy to use in groovy.

UPDATE: changed type of the example variable to List, as the example file's top level element is a collection

@Grab('org.yaml:snakeyaml:1.17')

import org.yaml.snakeyaml.Yaml

Yaml parser = new Yaml()
List example = parser.load(("example.yaml" as File).text)

example.each{println it.subject}

Full documentation of snakeyaml:

https://bitbucket.org/asomov/snakeyaml/wiki/Documentation

Answer 2

FWIW, the upcoming (as time of this writing) Groovy version 3.0 has direct support for yaml: http://docs.groovy-lang.org/next/html/api/groovy/yaml/package-summary.html with the traditional YamlSlurper / YamlBuilder combo You could always switch to this not-yet-officially-released version.

[Edited] that version 3.0.x is now officially available, with the groovy.yaml package http://docs.groovy-lang.org/latest/html/api/groovy/yaml/package-summary.html

Answer 3

Here is an example: https://github.com/apache/groovy/blob/bdb2f7a482a4daec2bee01acd5590241c356e966/subprojects/groovy-yaml/src/spec/test/groovy/yaml/YamlParserTest.groovy#L83

BTW, multiple docs in one yaml file is supported since Groovy 4.0.0. For example, https://github.com/apache/groovy/blob/bdb2f7a482a4daec2bee01acd5590241c356e966/subprojects/groovy-yaml/src/spec/test/groovy/yaml/YamlParserTest.groovy#L109