Getmethod Mokito java mock

So i'm trying to use mockito to mock a getMethod request/responce. However i am having some problems

@Mock
private HttpClient client;
private GetMethod method;

@InjectMocks
private WebserviceInterface webserviceInterface;

@Before
public void setUp() throws Exception {
    initMocks(this);
    setting up the a valid customer happens here

}


@Test
public void shouldReturnValidCustomerWithValidBarcode() throws Exception {
    // TODO: Mock out the ParcelService so that we can specify what JSON data is returned.
    // TODO: Create the Customer object that we expect
    // TODO: Call the method of module under test
    // TODO: assertThat(expected, is(theActualObject)

    when(client.executeMethod(any(HttpMethod.class))).thenReturn(200);

    String aValidCustomerJson = "JsonGoes Here";

    when(method.getResponseBodyAsString()).thenReturn(aValidCustomerJson);
   assertThat(webserviceInterface.parcelSearch("aValidBarcode"), is(aValidCustomer));


}

but im getting a null pointer exception and im not sure why:

java.lang.NullPointerException at com.springapp.mvc.WebserviceInterfaceTest.shouldReturnValidCustomerWithValidBarcode(WebserviceInterfaceTest.java:137)

Any help if aprriciated, Thanks