In the last chapter, we focused on injecting information from the header of an HTTP request. In this chapter, we will focus on the message body of an HTTP request and response. In the examples in previous chapters, we used low-level streaming to read in requests and write out responses. To make things easier, JAX-RS also allows you to marshal message bodies to and from specific Java types. It has a number of built-in providers, but you can also write and plug in your own providers. Let’s look at them all.
JAX-RS has a bunch of built-in handlers that can marshal to and from a few different specific Java types. While most are low-level conversions, they can still be useful to your JAX-RS classes.
We were first introduced to
StreamingOutput back in Chapter 3.
StreamingOutput is a simple callback interface that you implement when you want to do raw streaming of response bodies:
You allocate implemented instances of this interface and return them from your JAX-RS resource methods. When the JAX-RS runtime is ready to write the response body of the message, the
write() method is invoked on the
StreamingOutput instance. Let’s look at an example: