Bypass Serialization using `Readers` and `InputStreams`

Juneau serializers treat instances of Readers and InputStreams special by simply serializing their contents directly to the output stream or writer. This allows you to embed fully customized serializer output.

public class MyBean {
    // A bean property that produces raw JSON.
    public Reader f1 = new StringReader("{'foo':'bar'}");
}

// Produces "{f1:{'foo':'bar'}}"
String json = Json5.of(new MyBean());

Note that if you're serializing Readers and InputStreams, it's up to you to make sure you're producing valid output (in this case JSON).

A more typical scenario where this is useful is by using swaps to convert POJOs to Readers whose contents are determined via the BeanSession.getMediaType() method.

In the following example, we're customizing the JSON output for a particular bean type but leaving all other renditions as-is:

@Swap(MyBeanSwapSometimes.class)
public class MyBean {...}

// A swap that produces specialized output for JSON but default serialization for
// all other media types.
public class MyBeanSwapSometimes extends ObjectSwap {
    public Object swap(BeanSession session, MyPojo object) throws Exception {
        MediaType mediaType = session.getMediaType();
        if (mediaType.hasSubType("json"))
            return new StringReader("{myPojo:'foobar'}");  // Custom JSON output
        return object;  // Otherwise serialize it as a normal bean
    }
}

warning

Due to the nature of the RDF serializers, Readers and InputStreams are serialized as literals, not as RDF text. This is due to the fact that the RDF serializers use a DOM for serialization so we don't have access to the underlying stream.