Apache Storm-从Config中读取YAML列表

Question

I am writing a Apache Storm topology which takes in a configuration file on the command line. The configuration file is YAML and looks like this

#Ports
ports:
  - 9998
  - 9997
  - 9996

I load the configuration file into the Storm config using snakeyaml and the following code, resource is set to the string of the path of the configuration yaml file:

Config conf = new Config();
Yaml yaml = new Yaml()
Map rs = (Map) yaml.load(new InputStreamReader(new FileInputStream(resource)));
conf.putAll(rs);

I have verified that the Config object now contains the list of ports. If I print the the values of the "ports" it looks to be the following "[9998, 9997, 9996]".

My question is how to I get this into an Array, ArrayList, or any data structure I can use in Java? I have been using the backtype.storm.utils.Utils class which has a helper method get, but it only works when I have a single value not a list of values.

I have tried calling it like so:

 String[] ports = Utils.get(conf, "mimes", null); 

but, I get a casting exception. I have also tried:

 String ports = Utils.get(conf, "mimes", null); 

to check to see if I can just get the entire string and that also has a cast exception. I am not sure what the Config object is storing this list as. A Map?

Any help would be appreciated.

Answer 1

I would recommend using Jackson's YAML module ( https://github.com/FasterXML/jackson-dataformat-yaml ); this is what many frameworks like DropWizard do. If so, you can use data-binding exactly as with JSON, to construct POJOs for configuration access:

ObjectMapper mapper = new ObjectMapper(new YAMLFactory());
Config config = mapper.readValue(fileOrInputStream, Config.class);
int port = mapper.server.port; // or getters, or however your Config object is laid out

Answer 2

I am not sure what the answer is, but I ended up updating my snakeyaml version to 1.14 and I am now using the yaml.loadAs() method to directly load the cotents of the yaml file into a pojo. From there I am able to get what I need.