EmptyNullRepresenter.java

package wecui.config;

import org.yaml.snakeyaml.introspector.Property;
import org.yaml.snakeyaml.nodes.CollectionNode;
import org.yaml.snakeyaml.nodes.MappingNode;
import org.yaml.snakeyaml.nodes.Node;
import org.yaml.snakeyaml.nodes.NodeTuple;
import org.yaml.snakeyaml.nodes.SequenceNode;
import org.yaml.snakeyaml.nodes.Tag;
import org.yaml.snakeyaml.representer.Represent;
import org.yaml.snakeyaml.representer.Representer;

public class EmptyNullRepresenter extends Representer {

    public EmptyNullRepresenter() {
        super();
        this.nullRepresenter = new EmptyRepresentNull();
    }

    protected class EmptyRepresentNull implements Represent {

        public Node representData(Object data) {
            return representScalar(Tag.NULL, ""); // Changed "null" to "" so as to avoid writing nulls
        }
    }

    // Code borrowed from snakeyaml (http://code.google.com/p/snakeyaml/source/browse/src/test/java/org/yaml/snakeyaml/issues/issue60/SkipBeanTest.java)
    @Override
    protected NodeTuple representJavaBeanProperty(Object javaBean, Property property, Object propertyValue, Tag customTag) {
        NodeTuple tuple = super.representJavaBeanProperty(javaBean, property, propertyValue, customTag);
        Node valueNode = tuple.getValueNode();
        if (valueNode instanceof CollectionNode) {
            // Removed null check
            if (Tag.SEQ.equals(valueNode.getTag())) {
                SequenceNode seq = (SequenceNode) valueNode;
                if (seq.getValue().isEmpty()) {
                    return null; // skip empty lists
                }
            }
            if (Tag.MAP.equals(valueNode.getTag())) {
                MappingNode seq = (MappingNode) valueNode;
                if (seq.getValue().isEmpty()) {
                    return null; // skip empty maps
                }
            }
        }
        return tuple;
    }
    // End of borrowed code
}