`Nullpointer within io.restassured.internal.suppor

I'm building an integration-test using restAssured and Junit, and when calling the following code:

    private void login(){
    cookie = given()
            .baseUri("localhost:9000")
            .when()
            .formParam("username", "myUser")
            .formParam("password", "myPass")
            .formParam("realm", "realmParam")
            .post("/login")
            .then()
            .extract()
            .header("Set-Cookie");
}

i get the following error:

java.lang.NullPointerException: Cannot invoke method trim() on null object

at org.codehaus.groovy.runtime.NullObject.invokeMethod(NullObject.java:91)
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:48)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at org.codehaus.groovy.runtime.callsite.NullCallSite.call(NullCallSite.java:35)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:48)
at java_lang_String$trim.call(Unknown Source)
at io.restassured.internal.support.PathSupport.mergeAndRemoveDoubleSlash(PathSupport.groovy:28)
at io.restassured.internal.support.PathSupport$mergeAndRemoveDoubleSlash$0.callStatic(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallStatic(CallSiteArray.java:56)
at io.restassured.internal.support.PathSupport$mergeAndRemoveDoubleSlash$0.callStatic(Unknown Source)
at io.restassured.internal.RequestSpecificationImpl.getTargetPath(RequestSpecificationImpl.groovy:1450)
at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1212)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at io.restassured.internal.RequestSpecificationImpl.invokeMethod(RequestSpecificationImpl.groovy)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.call(PogoInterceptableSite.java:48)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.callCurrent(PogoInterceptableSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:166)
at io.restassured.internal.RequestSpecificationImpl.partiallyApplyPathParams(RequestSpecificationImpl.groovy:1751)
at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1212)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at io.restassured.internal.RequestSpecificationImpl.invokeMethod(RequestSpecificationImpl.groovy)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.call(PogoInterceptableSite.java:48)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.callCurrent(PogoInterceptableSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:182)
at io.restassured.internal.RequestSpecificationImpl.newFilterContext(RequestSpecificationImpl.groovy:1151)
at sun.reflect.GeneratedMethodAccessor32.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1212)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at io.restassured.internal.RequestSpecificationImpl.invokeMethod(RequestSpecificationImpl.groovy)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.call(PogoInterceptableSite.java:48)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.callCurrent(PogoInterceptableSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:182)
at io.restassured.internal.RequestSpecificationImpl.applyPathParamsAndSendRequest(RequestSpecificationImpl.groovy:1720)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1212)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at io.restassured.internal.RequestSpecificationImpl.invokeMethod(RequestSpecificationImpl.groovy)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.call(PogoInterceptableSite.java:48)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.callCurrent(PogoInterceptableSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:182)
at io.restassured.internal.RequestSpecificationImpl.applyPathParamsAndSendRequest(RequestSpecificationImpl.groovy:1728)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1212)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:812)
at io.restassured.internal.RequestSpecificationImpl.invokeMethod(RequestSpecificationImpl.groovy)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.call(PogoInterceptableSite.java:48)
at org.codehaus.groovy.runtime.callsite.PogoInterceptableSite.callCurrent(PogoInterceptableSite.java:58)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:182)
at io.restassured.internal.RequestSpecificationImpl.post(RequestSpecificationImpl.groovy:172)
at io.restassured.internal.RequestSpecificationImpl.post(RequestSpecificationImpl.groovy)
at discovery.utils.VMS.Requests.login(Requests.java:57)
at discovery.utils.VMS.Requests.<init>(Requests.java:16)
at discovery.utils.VMS.TestData.<init>(TestData.java:36)
at discovery.utils.VMS.TestData.<init>(TestData.java:30)
at discovery.users.EntitlementOverrideTest.overridenClientIsEntitledToAnyPackage(EntitlementOverrideTest.java:42)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

but I can't for the life of me figure out why! I've set a breakpoint on the line that throws and observed the input to that method, it turns out it is called many more times than I would expect from this test (the method concatenates 2 parts of a url) and the input that is actually defined in this failing test is processed without error. But then it is for some reason called a bunch of more times, on of which, invariably contains a null parameter and thus fails. Googling suggested there might be dependency-conflicts within my project, but I have been unable to find any.

To clarify, I'm not asking what a Nullpointer is, of that I am perfectly aware. Rather, it's the inner workings of rest-assured that has me confused.The nullpointer is merely the manifestation of my lacking understanding of this library's innards :)

whats going on?

I had the same problem. I could fix it by removing .baseUri("localhost:9000") and use .port(9000) to set the port.