Task implementation

package com.decisionbrain.kcoloringworker;

import com.decisionbrain.kcoloringworker.model.Coloration;
import com.decisionbrain.kcoloringworker.model.Map;
import com.decisionbrain.optimserver.common.parameter.Parameter;
import com.decisionbrain.optimserver.worker.api.ExecutionContext;
import com.decisionbrain.optimserver.worker.api.Task;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import ilog.concert.IloException;
import ilog.concert.IloIntVar;
import ilog.cp.IloCP;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class KColoringTask implements Task {

    static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
    private static final Logger LOGGER = LoggerFactory.getLogger(KColoringTask.class);

    @Override
    public void execute(Parameter input, Parameter output, ExecutionContext context) {
        // parse input k: the number of colors to be used for the coloration
        int k = Integer.parseInt(new String(input.get("k")));
        // create example map to be colored
        Map exampleMap = Map.createExampleMap();
        // create coloration to be filled in
        Coloration coloration = new Coloration();

        IloCP solver = new IloCP();
        solver.setOut(new Utils.Log4jInfoStream(LOGGER));
        solver.setWarning(new Utils.Log4jWarnStream(LOGGER));
        solver.setError(new Utils.Log4jErrorStream(LOGGER));
        try {
            // create variables
            for(String country : exampleMap.getCountries()) {
                solver.add(solver.intVar(1, k, country));
            }
            // create constraints
            for(String country : exampleMap.getCountries()) {
                for(String adjacentCountry : exampleMap.getAdjacentCountries(country)) {
                    solver.add(solver.neq(solver.getIloIntVar(country), solver.getIloIntVar(adjacentCountry)));
                }
            }
            solver.startNewSearch();
            int nbSolutions = 0;
            while(!context.shouldAbort() && solver.next()) { // stop if the user asked for job abortion
                nbSolutions++;
            }
            solver.endSearch();
            if(nbSolutions > 0) {
                // retrieve solution
                IloIntVar[] vars = solver.getAllIloIntVars();
                for (IloIntVar var : vars) {
                    coloration.setColor(var.getName(), (int) solver.getValue(var));
                }
            }
        } catch (IloException e) {
            LOGGER.warn("Error during model creation or resolution: ", e);
        }
        solver.end();

        // send coloration output
        LOGGER.info("Coloration found: {}", coloration);
        try {
            output.emit("coloration", OBJECT_MAPPER.writeValueAsBytes(coloration));
        } catch (JsonProcessingException e) {
            LOGGER.error("Error when serializing coloration output: ", e);
        }
    }
}