JSF h：selectOneMenu没有绑定对象

Question

所以，我有两个实体：InitialSituation，其中ManytoOne与Universe实体有关。 以InitialSituation的形式，选择Universe：

<h:selectOneMenu id="universe" value="#{initialSituationController.initialSituation.universe}" >
    <f:selectItems value="#{universeBean.selectItems}" />
</h:selectOneMenu>

实体（使用JPA注释）：

@Entity
@Table(name = "initial_situation")
public class InitialSituation implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO, generator = "initial_situation_id_seq")
    @SequenceGenerator(name = "initial_situation_id_seq", sequenceName = "initial_situation_id_seq", allocationSize = 1)
    @Column(name = "id_initial_situation")
    protected int idInitialSituation;
    protected String name;
    protected String content;
    protected boolean happy;
    @ManyToOne
    @JoinColumn(name = "id_universe")
    protected Universe universe;

    // Getters and setters
}

@Entity
@Table(name = "universe")
public class Universe implements Serializable {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO, generator="universe_id_seq")
    @SequenceGenerator(name="universe_id_seq", sequenceName="universe_id_seq", allocationSize=1)
    @Column( name = "id_universe" )
    protected int idUniverse;
    @Column
    protected String name;
    @Column
    protected String content;
    @OneToMany(mappedBy = "universe")
    protected List<InitialSituation> initialSituations;

    public List<InitialSituation> getInitialSituations() {
        return initialSituations;
    }

    public void setInitialSituations(List<InitialSituation> initialSituations) {
        this.initialSituations = initialSituations;
    }

    @Override
    public String toString(){
        return this.getName();
    }
}

呈现的HTML中的select具有正确的值和标签。但是selectOneMenu和value =“＃{initialSituationController.initialSituation.universe}”之间的绑定不起作用。 然而，我验证了InitialSituation有一个Universe，

为什么绑定不起作用？谢谢！

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