public String getStringHeader(Message in, String header, String defaultValue) {
        String headerValue = in.getHeader(header, String.class);
        return ObjectHelper.isNotEmpty(headerValue) ? headerValue : defaultValue;
    }
@Test
    public void testGetStringHeaderWithEmptySrting() {
        when(in.getHeader(HEADER_METRIC_NAME, String.class)).thenReturn("");
        assertThat(okProducer.getStringHeader(in, HEADER_METRIC_NAME, "value"), is("value"));
        inOrder.verify(in, times(1)).getHeader(HEADER_METRIC_NAME, String.class);
        inOrder.verifyNoMoreInteractions();
    }