Debugging and setting breakpoints in Java code built with Gradle

I am using Emacs (v24.4) for writing Java applications. I have created a Java library that I am building using Gradle (v2.2) and testing with Spock Framework where I have all my test cases.

I would like to debug my Java code using Emacs. However, I haven't found any way of doing this. I would like to set a breakpoint and step through my Java code.

Here is my Gradle build file:

apply plugin: 'java'
apply plugin: 'groovy'

repositories {
    mavenCentral()
}

dependencies {
    compile 'org.igniterealtime.smack:smack-core:4.1.0'
    compile 'org.igniterealtime.smack:smack-tcp:4.1.0'

    testCompile 'org.spockframework:spock-core:0.7-groovy-2.0'
    testCompile 'org.codehaus.groovy:groovy:2.3.6'
}

jar {
    baseName = 'SunSmackClient'
    version = '1.0.0'
}

gradle.projectsEvaluated {
    tasks.withType(JavaCompile) {
        options.compilerArgs << '-Xlint:unchecked'
   }
}

task wrapper(type: Wrapper) {
    gradleVersion = '2.1'
}

Example Spock Framework test:

public class SmackClientSpec extends Specification {
    private SmackClient smackClient;

    /* Test 1 */
    @IgnoreRest
    def 'Create a connection to XMPP server'() {
        setup: /* Setup connection object */

        def domain = 'domain'  
        def username = 'username'
        def password = 'password'

        SmackClient smackClient = new SmackClient()

        expect: /* Connection to return true */
        smackClient.createConnection(domain, username, password) == true
    }
}

Many thanks in advance.