Jackson kann nicht auf com.fasterxml.jackson.core.ObjectCodec zugreifen

Diese Frage ist eine Folge von dieser . Ich kann anscheinend nicht auf die Jackson-Bibliothek im folgenden Code zugreifen:

import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import com.fasterxml.jackson.databind.ObjectWriter;
import Java.io.IOException;
import Java.util.ArrayList;
import Java.util.List;

public class ServerConfiguration {
    public String info = null;
    public String idlURL = null;
    public String idlContents = null;
    public List<ServerInfo> servers = new ArrayList<>();

    public final void clear() {
        info = null;
        idlURL = null;
        idlContents = null;
        if (servers != null)
            servers.clear();
    }

    private final static ObjectReader jsonReader;
    private final static ObjectWriter jsonWriter;

    static {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true); // <== Error:(52, 15) Java: cannot access com.fasterxml.jackson.core.JsonGenerator class file for com.fasterxml.jackson.core.JsonGenerator not found
        //mapper.configure(SerializationFeature.WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED, true);
        jsonWriter = mapper.writer();
        jsonReader = mapper.reader(ServerConfiguration.class);
    }

    public static ServerConfiguration fromJson(String json) throws IOException {
        return jsonReader.<ServerConfiguration>readValue(json); // <== Error:(59, 26) Java: cannot access com.fasterxml.jackson.core.JsonProcessingException class file for com.fasterxml.jackson.core.JsonProcessingException not found
    }

    public String toJson() throws IOException {
        return jsonWriter.writeValueAsString(this);
    }

}

die JAR-Dateien befinden sich jedoch im Klassenpfad (Autocomplete zeigt die Methodendeklaration in Intellij an). 

Was vermisse ich?