EnumSets - problem on Yaml.load()?

[richard...@cyphergenomics.com]

I am trying to load an EnumSet using YAML, and get an exception "Cannot create property=setOfDays for JavaBean...". Please can you tell me what am I doing something wrong?  Are EnumSets not supported?

The enum:

public enum Day {

    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY

}

The code (condensed down):

import com....exploration.Day;

public class YamlEnumSetTest {

Day day;

EnumSet<Day> setOfDays;

public Day getDay() {

return this.day;

}

public void setDay(Day day) {

this.day = day;

}

public EnumSet<Day> getSetOfDays() {

return this.setOfDays;

}

public void setSetOfDays(EnumSet<Day> setOfDays) {

this.setOfDays = setOfDays;

}

public static void main(String[] args) {

YamlEnumSetTest yEST = new YamlEnumSetTest();

yEST.day = Day.SUNDAY;

yEST.setOfDays = EnumSet.of(Day.MONDAY, Day.WEDNESDAY, Day.FRIDAY);

System.out.println(yEST.day + " : " + yEST.setOfDays);

Yaml yaml = new Yaml();

String output = yaml.dump(yEST);

System.out.println(output);

YamlEnumSetTest newYEST = (YamlEnumSetTest) yaml.load(output);

System.out.println(newYEST.day + " : " + newYEST.setOfDays);

}

}

The result is (with package names elided):

SUNDAY : [MONDAY, WEDNESDAY, FRIDAY]

!!com....exploration.YamlEnumSetTest

day: SUNDAY

setOfDays: !!set {!!com....exploration.Day 'MONDAY': null,

  !!com....exploration.Day 'WEDNESDAY': null, !!com....exploration.Day 'FRIDAY': null}

Exception in thread "main" Cannot create property=setOfDays for JavaBean=com....exploration.YamlEnumSetTest@782830e

 in 'string', line 1, column 1:

    !!com.... ... 

    ^

argument type mismatch

 in 'string', line 3, column 12:

    setOfDays: !!set {!!com.... ... 

               ^

at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:312)

at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:189)

at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:345)

at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182)

at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:141)

at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:127)

at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:450)

at org.yaml.snakeyaml.Yaml.load(Yaml.java:369)

at com.cyphergenomics.qa.framework.exploration.YamlEnumSetTest.main(YamlEnumSetTest.java:34) <-- The yaml.load(output) line

Caused by: java.lang.IllegalArgumentException: argument type mismatch

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:497)

at org.yaml.snakeyaml.introspector.MethodProperty.set(MethodProperty.java:48)

at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:310)

... 8 more

Thanks in advance for your help.

[maslovalex]

Hi,

I am not really sure you can do it with current SnakeYAML.
EnumSet needs Enum class to be instantiated (e.g. EnumSet.noneOf(...), Enum.of(...)) and SnakeYAML is not really friendly with classes without default constructor :)

You can try to create CustomConstructor for the EnumSet, but then you need to figure out Parameter class of the EnumSet. And I think the only way to do it now is to analyze types of keyNodes from mappingNode.getValue().
If you implement this kind of solution, please, share it with us.

You can also try to use my SnakeYAML's clone https://bitbucket.org/maslovalex/snakeyaml (hopefully we merge it to master some day).
It does not provide general solution. But some.

Yaml yaml = new Yaml();

TypeDescription yamlEnumSetTD = new TypeDescription(YamlEnumSetTest.class) {
    @Override
    public Object newInstance(String propertyName, Node node) {
        if ("setOfDays".equals(propertyName)) {
            node.setTwoStepsConstruction(true);
            return EnumSet.noneOf(Day.class);
        }
        return super.newInstance(propertyName, node);
    }
};

yaml.addTypeDescription(yamlEnumSetTD);

This is per class solution, not just for any EnumSet.
It dumps and loads class from your Example as well as it's more concise representation :  

"!!org.yaml.snamkeyaml.examples.enumset.YamlEnumSetTest\n  setOfDays: { MONDAY, WEDNESDAY, FRIDAY }\n  day: SUNDAY\n"

Hope it helps at least somehow.

-Alex

[Richard Spooner]

Hi Alex,

Thank you for your quick response. Your suggestion will work for me as I only have one EnumSet I need to manipulate. However, I get a compilation problem. The steps I took are:

1. I updated my mvn environment to take 1.17-SNAPSHOT from bitbucket. I had to do a mvn dependency:purge-local-repository to pick up the snapshot. I saw the following lines:

Downloading: http://oss.sonatype.org/content/groups/public/org/yaml/snakeyaml/1.17-SNAPSHOT/snakeyaml-1.17-20151003.070211-37.pom

Downloaded: http://oss.sonatype.org/content/groups/public/org/yaml/snakeyaml/1.17-SNAPSHOT/snakeyaml-1.17-20151003.070211-37.pom (26 KB at 13.6 KB/sec)

...

Downloading: http://oss.sonatype.org/content/groups/public/org/yaml/snakeyaml/1.17-SNAPSHOT/snakeyaml-1.17-20151003.070211-37.jar

Downloaded: http://oss.sonatype.org/content/groups/public/org/yaml/snakeyaml/1.17-SNAPSHOT/snakeyaml-1.17-20151003.070211-37.jar (266 KB at 194.7 KB/sec)

so I should have the latest and greatest snapshot available. FWIW, I'm using Eclipse 4.5.0 (Mars) and its mvn plug-in. The  mvn dependency:purge-local-repository was done on the command line.

2.  I restarted Eclipse.

3.  I added your suggested code. adding import org.yaml.snakeyaml.TypeDescription and import org.yaml.snakeyaml.nodes.Node  My main() is now:

public static void main(String[] args) {

YamlEnumSetTest yEST = new YamlEnumSetTest();

yEST.day = Day.SUNDAY;

yEST.setOfDays = EnumSet.of(Day.MONDAY, Day.WEDNESDAY, Day.FRIDAY);

System.out.println(yEST.day + " : " + yEST.setOfDays);

Yaml yaml = new Yaml();

TypeDescription yamlEnumSetTD = new TypeDescription(YamlEnumSetTest.class) {   <-- Compilation problem #1

   @Override

   public Object newInstance(String propertyName, Node node) {    <-- Compilation problem #2

       if ("setOfDays".equals(propertyName)) {

           node.setTwoStepsConstruction(true);

           return EnumSet.noneOf(Day.class);

       }

       return super.newInstance(propertyName, node);  <-- Compilation problem #3

   }

};

yaml.addTypeDescription(yamlEnumSetTD);

String output = yaml.dump(yEST);

System.out.println(output);

YamlEnumSetTest newYEST = (YamlEnumSetTest) yaml.load(output);

System.out.println(newYEST.day + " : " + newYEST.setOfDays);

}

4.  Java complains three times: 

• Error #1: "An anonymous class cannot subclass the final class TypeDescription" on the TypeDescription yamlEnumSetTD = ... line.
  
• Error #2: "The method newInstance(String, Node) of type new TypeDescription(){} must override or implement a supertype method" on the public Object newInstance(... line.
  
• Error #3: "The method newInstance(String, Node) is undefined for the type Object" on the return super.newInstance line.
  

Any ideas?

Thanks again for your help.

/Richard

Richard Spooner

Senior QA Manager

Cypher Genomics, Inc.

9255 Towne Centre Drive, Suite 340

San Diego, CA 92121

P: (858) 207-6300 x209

F: (858) 346-9110

www.cyphergenomics.com

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[maslovalex]

As I mentioned in previous reply : this will only work if you use my clone of SnakeYAML (which hopefully we will merge to master at some point)

$ hg clone https://bitbucket.org/maslovalex/snakeyaml snakeyaml-beancontrol
$ cd snakeyaml-beancontrol
$ mvn clean install

after that those compilation errors should be gone.

-Alex