A request can only have one entity body, that's why the restriction. The only option I can think of is to use multipart request, where you can have multiple body parts.
Example server side
@Path("multipart")
public class MultipartResource {
    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    public Response doPost(@FormDataParam("emp") Emp emp,
                           @FormDataParam("student") Student student) {
        StringBuilder builder = new StringBuilder();
        builder.append("Emp:").append(emp.name).append("\n");
        builder.append("Student:").append(student.name).append("\n");
        return Response.ok(builder.toString()).build();
    }
    public static class Student {
        public String name;
    }
    public static class Emp {
        public String name;
    }
}
Client side
public class Main {
    public static void main(String[] args) throws Exception {
        Client client = Client.create();
        Emp emp = new Emp();
        emp.name = "pee";
        Student stu = new Student();
        stu.name = "skillet";
        FormDataMultiPart multipart = new FormDataMultiPart()
                .field("emp", emp, MediaType.APPLICATION_JSON_TYPE)
                .field("student", stu, MediaType.APPLICATION_JSON_TYPE);
        final String url = "http://localhost:8080/api/multipart";
        String response = client.resource(url).type(MediaType.MULTIPART_FORM_DATA_TYPE)
                .post(String.class, multipart);
        System.out.println(response);   
    }
}
Result:
Emp:pee
  Student:skillet
Jersey dependency for multipart support.
<dependency>
    <groupId>com.sun.jersey.contribs</groupId>
    <artifactId>jersey-multipart</artifactId>
    <version>${jersey1.version}</version>
</dependency>