How to define a map in a YAML file for simple POJO?

Question

I am using SnakeYAML to parse certain configuration/property values to a Configuration object (defined below).

My YAML file looks like this:

# Thread
batchLimit: 1000
threadCountLimit: 2

# Some more config
key: value

# Map
keyMapping: <What goes here?>

My Configuration class looks like this:

public class Configuration{
  int batchlimit;
  int threadCountLimit;
  ...
  Map<String,String> keyMapping;
}

How do I define the keyMapping in the YAML file so it can be parsed directly by SnakeYAML?

score 103 · Accepted Answer · edited Apr 16 '17 at 01:55

103

Here is how it can look like:

#MAP
keyMapping: 
    key1: value1
    key2: value2

Generally YAML format has natural support of key-value pairs. Take a look on the following tutorial (just for example): https://github.com/Animosity/CraftIRC/wiki/Complete-idiot's-introduction-to-yaml

Or just google "yaml map" for more details.

edited Apr 16 '17 at 01:55

rbento

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answered Dec 17 '15 at 07:21

AlexR

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Thanks a lot. Didn't even think of trying this. Was getting weird results like using '?' for keys and ':' for values. You saved so much of my time – frugalcoder Dec 17 '15 at 10:18
8

I also googled yml map and ended up here. Just a future idea type in a link instead, or stop typing.....While you are ahead. It was a really nice answer. :) – PlickPlick Nov 29 '19 at 09:38

score 4 · Answer 2 · answered May 11 '20 at 05:21

Yaml file "AppParams.yml" with key-value pairs:

someConfig:
    key1: value1
    key2: value2

POJO:

public class ApplicationParameters {
    private Map<String, String> someConfig;

    public ApplicationParameters() {
    }

    public Map<String, String> getSomeConfig() {
        return someConfig;
    }

    public void setSomeConfig(Map<String, String> someConfig) {
        this.someConfig = someConfig;
    }
}

Reader:

ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
File paramFile = new File("AppParams.yml");
ApplicationParameters applicationParameters = mapper.readValue(paramFile, ApplicationParameters.class);

Map<String, String> someConfig = applicationParameters.getSomeConfig();

String key1Value = someConfig.get("key1");    //returns "value1"

The example above uses these dependencies in POM.xml:

 <dependencies>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.9.8</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.8</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-yaml</artifactId>
        <version>2.9.8</version>
    </dependency>
</dependencies>

How to define a map in a YAML file for simple POJO?

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