Per-media-type PojoSwaps

Swaps can also be defined per-media-type.

The {@link oaj.transform.PojoSwap#forMediaTypes()} method can be overridden to provide a set of media types that the swap is invoked on. It's also possible to define multiple swaps against the same POJO as long as they're differentiated by media type. When multiple swaps are defined, the best-match media type is used.

In the following example, we define 3 swaps against the same POJO. One for JSON, one for XML, and one for all other types.

public class PojoSwapTest { public static class MyPojo {} public static class MyJsonSwap extends StringSwap<MyPojo> { @Override /* PojoSwap */ public MediaType[] forMediaTypes() { return MediaType.forStrings("*/json"); } @Override /* PojoSwap */ public String swap(BeanSession session, MyPojo o) throws Exception { return "It's JSON!"; } } public static class MyXmlSwap extends StringSwap<MyPojo> { @Override /* PojoSwap */ public MediaType[] forMediaTypes() { return MediaType.forStrings("*/xml"); } @Override /* PojoSwap */ public String swap(BeanSession session, MyPojo o) throws Exception { return "It's XML!"; } } public static class MyOtherSwap extends StringSwap<MyPojo> { @Override /* PojoSwap */ public MediaType[] forMediaTypes() { return MediaType.forStrings("*/*"); } @Override /* PojoSwap */ public String swap(BeanSession session, MyPojo o) throws Exception { return "It's something else!"; } } @Test public void doTest() throws Exception { SerializerGroup g = SerializerGroup.create() .append(JsonSerializer.class, XmlSerializer.class, HtmlSerializer.class) .sq() .pojoSwaps(MyJsonSwap.class, MyXmlSwap.class, MyOtherSwap.class) .build(); MyPojo myPojo = new MyPojo(); String json = g.getWriterSerializer("text/json").serialize(myPojo); assertEquals("'It\\'s JSON!'", json); String xml = g.getWriterSerializer("text/xml").serialize(myPojo); assertEquals("<string>It's XML!</string>", xml); String html = g.getWriterSerializer("text/html").serialize(myPojo); assertEquals("<string>It's something else!</string>", html); } }

When multiple swaps match the same media type, a best-match algorithm is applied to find the correct swap to use.

In later sections we describe how annotations can be used to shorten this syntax:

@Swaps({MyJsonSwap.class,MyXmlSwap.class,MyOtherSwap.class}) public static class MyPojo {} @Swap(mediaTypes="*/json") public static class MyJsonSwap extends PojoSwap<MyPojo,String> {...} @Swap(mediaTypes="*/xml") public static class MyXmlSwap extends PojoSwap<MyPojo,String> {...} @Swap(mediaTypes="*/*") public static class MyOtherSwap extends PojoSwap<MyPojo,String> {...}