Howto keep session in HttBuilder with cookies

RestChartSpec.groovy

package eu.spoonman.specs.rest

import groovyx.net.http.ContentType
import groovyx.net.http.Method
import eu.spoonman.connectors.RestConnector
import spock.lang.Specification
import spock.lang.Shared
import spock.lang.Stepwise

@Stepwise
class RestChartSpec extends Specification {
    @Shared
    RestConnector restConnector

    def setupSpec() {
        restConnector = new RestConnector('http://localhost:8080')
    }

    def "should login as test"() {
        given:
            Map params = [j_username: 'test', j_password: 'test']
        when:
            restConnector.request(Method.POST, ContentType.ANY, '/frontoffice/j_spring_security_check', params)
        then:
            !(restConnector.cookies.empty)
    }

    def "should allow access to chart data series"() {
        given:
            Map params = [days: 14]
        when:
            Map result = restConnector.request(Method.POST, ContentType.JSON, "$BASE_URL/chart/series", params)
        then:
            result != null
            result.series.size() > 0
    }
}

RestConnector.groovy

package eu.spoonman.connectors.RestConnector

import groovyx.net.http.Method
import groovyx.net.http.ContentType
import groovyx.net.http.HTTPBuilder
import groovyx.net.http.HttpResponseDecorator
 
class RestConnector {
    private String baseUrl
    private HTTPBuilder httpBuilder
    private List<String> cookies
 
    RestConnector(String url) {
        this.baseUrl = url
        this.httpBuilder = initializeHttpBuilder()
        this.cookies = []
    }
 
    public request(Method method, ContentType contentType, String url, Map<String, Serializable> params) {
        debug("Send $method request to ${this.baseUrl}$url: $params")
        httpBuilder.request(method, contentType) { request ->
            uri.path = url
            uri.query = params
            headers.put('Cookie', cookies.join(';'))
        }
    }
 
    private HTTPBuilder initializeHttpBuilder() {
        def httpBuilder = new HTTPBuilder(baseUrl)
 
        httpBuilder.handler.success = { HttpResponseDecorator resp, reader ->
            resp.getHeaders('Set-Cookie').each {
                // [Set-Cookie: JSESSIONID=E68D4799D4D6282F0348FDB7E8B88AE9; Path=/frontoffice/; HttpOnly]
                String cookie = it.value.split(';')[0]
                debug("Adding cookie to collection: $cookie")
                cookies.add(cookie)
            }
            debug("Response: ${reader}")
            return reader
        }
        return httpBuilder
    }
 
    private debug(String message) {
        System.out.println(message) //for Gradle
    }
}