Document ways of customizing ObjectMapper for JacksonDataFormat

Fixes #3921

docs/modules/ROOT/pages/reference/extensions/jackson.adoc

@@ -38,3 +38,80 @@ Or add the coordinates to your existing project:
 ----
 
 Check the xref:user-guide/index.adoc[User guide] for more information about writing Camel Quarkus applications.
+
+== Usage
+
+=== Configuring the Jackson `ObjectMapper`
+
+There are a few ways of configuring the `ObjectMapper` that the `JacksonDataFormat` uses. These are outlined below.
+
+==== `ObjectMapper` created internally by `JacksonDataFormat`
+
+By default, `JacksonDataFormat` will create its own `ObjectMapper` and use the various configuration options on the `DataFormat`
+to configure additional Jackson modules, pretty printing and other features.
+
+==== Custom `ObjectMapper` for `JacksonDataFormat`
+
+You can pass a custom `ObjectMapper` instance to `JacksonDataFormat` as follows.
+
+[source,java]
+----
+ObjectMapper mapper = new ObjectMapper();
+JacksonDataFormat dataFormat = new JacksonDataFormat();
+dataFormat.setObjectMapper(mapper);
+----
+
+==== Using the Quarkus Jackson `ObjectMapper` with `JacksonDataFormat`
+
+The Quarkus Jackson extension exposes an `ObjectMapper` CDI bean which can be discovered by the `JacksonDataFormat`.
+
+[source,java]
+----
+ObjectMapper mapper = new ObjectMapper();
+JacksonDataFormat dataFormat = new JacksonDataFormat();
+// Make JacksonDataFormat discover the Quarkus Jackson `ObjectMapper` from the Camel registry
+dataFormat.setAutoDiscoverObjectMapper(true);
+----
+
+If you are using the JSON binding mode in the Camel REST DSL and want to use the Quarkus Jackson `ObjectMapper`, it can be achieved as follows.
+
+[source,java]
+----
+@ApplicationScoped
+public class Routes extends RouteBuilder() {
+    public void configure() {
+        restConfiguration().dataFormatProperty("autoDiscoverObjectMapper", "true");
+        // REST definition follows...
+    }
+}
+----
+
+You can perform customizations on the Quarkus `ObjectMapper` with a `ObjectMapperCustomizer`.
+
+[source,java]
+----
+@Singleton
+public class RegisterCustomModuleCustomizer implements ObjectMapperCustomizer {
+    public void customize(ObjectMapper mapper) {
+        mapper.registerModule(new CustomModule());
+    }
+}
+----
+
+It's also possible to `@Inject` the Quarkus `ObjectMapper` and pass it to the `JacksonDataFormat`.
+
+[source,java]
+----
+@ApplicationScoped
+public class Routes extends RouteBuilder() {
+    @Inject
+    ObjectMapper mapper;
+
+    public void configure() {
+        JacksonDataFormat dataFormat = new JacksonDataFormat();
+        dataFormat.setObjectMapper(mapper);
+        // Routes definition follows...
+    }
+}
+----
+

extensions/jackson/runtime/src/main/doc/usage.adoc

@@ -0,0 +1,73 @@
+=== Configuring the Jackson `ObjectMapper`
+
+There are a few ways of configuring the `ObjectMapper` that the `JacksonDataFormat` uses. These are outlined below.
+
+==== `ObjectMapper` created internally by `JacksonDataFormat`
+
+By default, `JacksonDataFormat` will create its own `ObjectMapper` and use the various configuration options on the `DataFormat`
+to configure additional Jackson modules, pretty printing and other features.
+
+==== Custom `ObjectMapper` for `JacksonDataFormat`
+
+You can pass a custom `ObjectMapper` instance to `JacksonDataFormat` as follows.
+
+[source,java]
+----
+ObjectMapper mapper = new ObjectMapper();
+JacksonDataFormat dataFormat = new JacksonDataFormat();
+dataFormat.setObjectMapper(mapper);
+----
+
+==== Using the Quarkus Jackson `ObjectMapper` with `JacksonDataFormat`
+
+The Quarkus Jackson extension exposes an `ObjectMapper` CDI bean which can be discovered by the `JacksonDataFormat`.
+
+[source,java]
+----
+ObjectMapper mapper = new ObjectMapper();
+JacksonDataFormat dataFormat = new JacksonDataFormat();
+// Make JacksonDataFormat discover the Quarkus Jackson `ObjectMapper` from the Camel registry
+dataFormat.setAutoDiscoverObjectMapper(true);
+----
+
+If you are using the JSON binding mode in the Camel REST DSL and want to use the Quarkus Jackson `ObjectMapper`, it can be achieved as follows.
+
+[source,java]
+----
+@ApplicationScoped
+public class Routes extends RouteBuilder() {
+    public void configure() {
+        restConfiguration().dataFormatProperty("autoDiscoverObjectMapper", "true");
+        // REST definition follows...
+    }
+}
+----
+
+You can perform customizations on the Quarkus `ObjectMapper` with a `ObjectMapperCustomizer`.
+
+[source,java]
+----
+@Singleton
+public class RegisterCustomModuleCustomizer implements ObjectMapperCustomizer {
+    public void customize(ObjectMapper mapper) {
+        mapper.registerModule(new CustomModule());
+    }
+}
+----
+
+It's also possible to `@Inject` the Quarkus `ObjectMapper` and pass it to the `JacksonDataFormat`.
+
+[source,java]
+----
+@ApplicationScoped
+public class Routes extends RouteBuilder() {
+    @Inject
+    ObjectMapper mapper;
+
+    public void configure() {
+        JacksonDataFormat dataFormat = new JacksonDataFormat();
+        dataFormat.setObjectMapper(mapper);
+        // Routes definition follows...
+    }
+}
+----