Supplementary example for decoder, and hamcrest usecase

[havenqi]

In my situation, the http body is an xml String. In order to use the easier way provided by Groovy, I manipulated it successfully in Xml Node way to avert the complex xpath processing(with your support in issue109.

1. The decoder part (looks tedious, welcome to suggest better way)

decoder('application/xml; charset=utf-8') { byte[] bytes, DecodingContext ctx ->
                    new XmlParser().parseText(new BufferedReader(new InputStreamReader(new ByteArrayInputStream(bytes), "utf-8")).readLine())
                }

2. The expectation part, "Sndt" is one of the node name in the XML, the depth is not fixed.

body hasValue("Sndt","$_Sndt"), 'application/xml; charset=utf-8'

3. A very simple Hamcrest method, which can be further refined to a more groovy style

def hasValue(String field, String value) {
        new TypeSafeMatcher() {
            @Override
            protected boolean matchesSafely(Object o) {
                if (o.'**'.find { node ->
                    node."$field".text() == value
                }) return true
                else return false
            }

            @Override
            void describeTo(Description description) {
                description.appendText("Expected Value:").appendValue(value)
            }
            @Override
            protected void describeMismatchSafely(Object o, Description mismatchDescription) {
                mismatchDescription.appendText("was ").appendValue(o.MsgHeader."$field".text())
            }
        }
    }

I believe more examples to decoder and hamcrest usage in common use cases(like XML, Json manipulation) can be helpful to new users.