<dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet</artifactId>
            <version>3.0-M1</version>
        </dependency>
        <dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet.ext.json</artifactId>
            <version>3.0-M1</version>
        </dependency>
        <dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet.ext.jaxrs</artifactId>
            <version>3.0-M1</version>
            <exclusions>
                <exclusion>
                    <artifactId>stax-api</artifactId>
                    <groupId>javax.xml.stream</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <!-- Must be before org.restlet.ext.jackson!!!! -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.6</version>
        </dependency>
        <dependency>
            <groupId>org.restlet.jse</groupId>
            <artifactId>org.restlet.ext.jackson</artifactId>
            <version>3.0-M1</version>
            <exclusions>
                <exclusion>
                    <artifactId>stax-api</artifactId>
                    <groupId>javax.xml.stream</groupId>
                </exclusion>
            </exclusions>
        </dependency>

    @Path("rest/inout")
    @POST
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    public MyOutputType inout(MyInputType input) {
        // Do some Stuff
        return result;
    }

It is very important to use bean classes to get default BeanSerializer of jackson.

    requires org.restlet.ext.jackson;
    exports info.elsener.package to com.fasterxml.jackson.databind;
    exports info.elsener.package to org.restlet.ext.jaxrs;

The line 'requires org.restlet.ext.jackson;' is needed to provide the 'JacksonConverter' to your project. Otherwise it will not be automatic recognized by restlet.

The lines 'exports ….' will allow jaxrs and jackson to read and write your Input/Output-Types.