持久化OneToMany实体会产生javax.faces.el.EvaluationException: javax.ejb.EJBException

Question

当我尝试save方法时，它会给我一个错误，但是当我尝试手动将数据直接插入数据库时，它工作得很好。有没有什么东西没有在我的managedbean类中添加或看到？请尽量保持简单明了的解释。谢谢

@Entity
@Table(name = "state")
@NamedQueries({
        @NamedQuery(name = "State.findAll", query = "SELECT s FROM State s"),
        @NamedQuery(name = "State.findByStateId", query = "SELECT s FROM State s WHERE s.stateId = :stateId"),
        @NamedQuery(name = "State.findByStateName", query = "SELECT s FROM State s WHERE s.stateName = :stateName")})
public class State implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "state_id")
    private Integer stateId;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "state_name")
    private String stateName;
    @JoinColumn(name = "country_id", referencedColumnName = "country_id")
    @ManyToOne(optional = false)
    private Country countryId;
}

这是国家/地区实体

@Entity
@Table(name = "country")
@NamedQueries({
    @NamedQuery(name = "Country.findAll", query = "SELECT c FROM Country c"),
    @NamedQuery(name = "Country.findByCountryId", query = "SELECT c FROM Country c WHERE c.countryId = :countryId"),
    @NamedQuery(name = "Country.findByCountryName", query = "SELECT c FROM Country c WHERE c.countryName = :countryName")})
public class Country implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "country_id")
    private Integer countryId;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 45)
    @Column(name = "country_name")
    private String countryName;
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "countryId")
    private List<State> stateList;
}

ManagedBean

public class stateManagedBean {
    @EJB
    private SessionBean sessionBean;
    @EJB
    private stateSessionBean stateSessionBean;
    private State state = new State();

    public stateManagedBean() {

    }
    public State getState() {
        return state;
    }

    public void setState(State state) {
        this.state = state;
    }

    public void save(){
        stateSessionBean.persist(state);
    }        
}

错误页

javax.faces.el.EvaluationException: javax.ejb.EJBException
    at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:102)
    at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)



Caused by: javax.validation.ConstraintViolationException: Bean Validation constraint(s) violated while executing Automatic Bean Validation on callback event:'prePersist'. Please refer to embedded ConstraintViolations for details.
    at org.eclipse.persistence.internal.jpa.metadata.listeners.BeanValidationListener.validateOnCallbackEvent(BeanValidationListener.java:90)
    at org.eclipse.persistence.internal.jpa.metadata.listeners.BeanValidationListener.prePersist(BeanValidationListener.java:62)
    at org.eclipse.persistence.descriptors.DescriptorEventManager.notifyListener(DescriptorEventManager.java:698)

Answer 1

正如异常日志清楚地指出的那样，您拥有一个ConstraintViolationException。在本例中，异常是由@NotNull注释引起的，该注释是由JPA实现中的PrePersist方法生成的。

删除stateId和stateName字段的@NotNull注释会有所帮助，但您的数据库可能会出现另一个异常。让您了解一下，如果@NotNull注释是由您的集成开发环境自动生成的，这可能是由于数据库表中的字段定义造成的。如果这是您的情况，并且您使用的是像我一样的MySql数据库，那么您将得到：

Internal Exception: java.sql.SQLException: Duplicate key or integrity constraint violation message from server: "Column 'state_id' cannot be null"

在这种情况下，您可能希望在bean中为State提供一个stateId和一个stateName (并避免删除@NotNull注释)：

state.setStateId(1);
state.setStateName("MyState");

最后，如果您还将country_id设置为非可选字段，如注释所示，那么在持久化它之前，还必须为您所在的州分配一个国家。