@Entity
public class ReportingForm implements Serializable {
    private static final long serialVersionUID = -719090596358868100L;
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Long report_id;
    @Column(length = 50)
    private String number_report_form;
    
    @Column(length = 200)
    private String name_report_form;
    
    @Column(length = 2000)
    private String description_report_form;
    
    @Temporal(javax.persistence.TemporalType.DATE)
    private Date date_upload;
    
    @Temporal(javax.persistence.TemporalType.DATE)
    private Date date_change;

    private Boolean enabled;
    
    @JoinTable(name="report_theme",joinColumns = @JoinColumn(name="theme_id"),
            inverseJoinColumns = @JoinColumn(name="report_id"))
    @ManyToMany(cascade = CascadeType.ALL)
    private final Collection<ThemeReportForm> themes;
    
    public ReportingForm(){
        this.themes=new ArrayList<>();
    }
//методы
}

@Entity
public class ThemeReportForm implements Serializable {
    private static final long serialVersionUID = 587929870245740900L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long theme_id;
    
    @Column(length = 10)
    private String code;
    
    @Column(length = 200)
    private String name;
}

    @GET
    @Path("/{id}")
    @Produces(MediaType.APPLICATION_JSON)
    public Response find(@PathParam("id") Long id) {
        T find = getEntityManager().find(entityClass, id);
        return Response.ok(find).build();
    }

            ReportingForm form = client.target(REST_SERVICE_URL).path("/{id}")
                    .resolveTemplate("id", g.getId()).request().get(ReportingForm.class);