using jackson for json to object

AttributesExample.java

public class AttributesExample {
    private String str = "foo";
    private double dbl = 0.8;
    private boolean bool = false;
    
    public String toString() { return str + ", " + dbl + ", " + bool; }
}

Main.java

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.google.gson.JsonElement;
import java.io.IOException;
import java.util.Map;


public class Main {
    public static void main(String[] args) {

        // ----------- instantiate class AttributesExample

        String json = "{" +
                "\"str\": \"hi\", " +
                "\"dbl\": 2.0, " +
                "\"bool\": true" +
                "}";

        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibility(PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY); // otherwise private fields won't be usable
        mapper.registerModule(new SimpleModule().addDeserializer(boolean.class, new JsonDeserializer<Boolean>() { // makes the boolean-parsing more solid, no more numbers allowed, but e.g. "True" or "FALSE" are valid 
            @Override
            public Boolean deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {
                String value = jsonParser.getValueAsString().toLowerCase();
                if (value.equals("true"))
                    return true;
                if (value.equals("false"))
                    return false;
                return null;
            }
        }));

        try {
            AttributesExample ae = mapper.readValue(json, AttributesExample.class);
            System.out.println(ae.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }

        // ----------- instantiate Map<ModelType, JsonElement>

        json = "{" +
            "\"OPTIMAL_STEPS_MODEL\": { "+
                "\"stepCircleResolution\": 18.0" +
            "}," +
            "\"FLOORFIELD\": {" +
                "\"potentialFieldResolution\": 0.1," +
                "\"timeCostAttributes\": {" +
                    "\"standardDerivation\": 0.7" +
            "}}}";

        try {
            Map<ModelType, JsonElement> result = mapper.readValue(json, new TypeReference<Map<ModelType, JsonElement>>() {});
            System.out.println(result.toString());
        } catch (IOException e) {
            e.printStackTrace();
            // --> ERROR: com.fasterxml.jackson.databind.JsonMappingException: Can not construct instance of com.google.gson.JsonElement, problem: abstract types either need to be mapped to concrete types, have custom deserializer, or be instantiated with additional type information
        }
    }
}

ModelType.java

public enum ModelType {
    OPTIMAL_STEPS_MODEL,
    FLOORFIELD
    //...
}

in zeile 35: nicht besser throw parse exception? wir wollen ja einen fehler erhalten, wenn ungültige eingaben sind. weiß aber nicht, welche exception class jackson verwendet.

in zeile 30: toLower() ist glaub ich falsch. bool in JSON darf nur "true" oder "false" sein (case sensitive!). siehe http://jsonlint.com/ und rfc 4627.