Corda provides a module that extends the popular Jackson serialisation engine. Jackson is often used to serialise to and from JSON, but also supports other formats such as YaML and XML. Jackson is itself very modular and has a variety of plugins that extend its functionality. You can learn more at the Jackson home page.

To gain support for JSON serialisation of common Corda data types, include a dependency on net.corda:jackson:XXX in your Gradle or Maven build file, where XXX is of course the Corda version you are targeting (0.9 for M9, for instance). Then you can obtain a Jackson ObjectMapper instance configured for use using the JacksonSupport.createNonRpcMapper() method. There are variants of this method for obtaining Jackson’s configured in other ways: if you have an RPC connection to the node (see “clientrpc”) then your JSON mapper can resolve identities found in objects.

The API is described in detail here:

import net.corda.jackson.JacksonSupport

val mapper = JacksonSupport.createNonRpcMapper()
val json = mapper.writeValueAsString(myCordaState)  // myCordaState can be any object.
import net.corda.jackson.JacksonSupport

ObjectMapper mapper = JacksonSupport.createNonRpcMapper()
String json = mapper.writeValueAsString(myCordaState)  // myCordaState can be any object.