java.lang.ClassCastException：java.lang.String 无法转换为 java.lang.Enum答案

【问题标题】：java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Enumjava.lang.ClassCastException：java.lang.String 无法转换为 java.lang.Enum
【发布时间】：2020-04-15 23:44:28
【问题描述】：

我在尝试将实体“UserAccount”持久保存到数据库表中时收到此错误。

@Entity
@Table(name = "user_account")
public class UserAccount extends BaseEntity {

  @OneToMany(cascade = CascadeType.ALL)
  @JoinColumn(name = "useraccount_id")
  @MapKeyEnumerated(EnumType.STRING)
  private Map<PhoneType, PhoneNumber> phones = new HashMap<PhoneType, PhoneNumber>();

  //... other attributes
  //... default constructor, getters and setters
}

public enum PhoneType {
  HOME("home"),
  MOBILE("mobile"),
  FAX("fax"),
  WORK("work");

  private String value;

  PhoneType(String value) {
     this.value = value;
  }

  @JsonValue
  public String getValue() {
      return value;
  }
}

@Entity
@Table(name = "phone_number")
public class PhoneNumber extends BaseEntity {

  private String areaCode;
  private String number;

  //... default constructor, getters and setters
}

最后..

public class UserAccountRepository {

    @Inject
    EntityManager entityManager;

    @Override
    public UserAccount save(UserAccount userAccount) {
        if (userAccount.getId() == null) {
            entityManager.persist(userAccount);
        } else {
            userAccount = entityManager.merge(userAccount);
        }
        return userAccount;
    }

  //.. other methods
}

Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Enum
    at org.eclipse.persistence.mappings.converters.EnumTypeConverter.convertObjectValueToDataValue(EnumTypeConverter.java:165)
    at org.eclipse.persistence.mappings.foundation.AbstractDirectMapping.extractIdentityFieldsForQuery(AbstractDirectMapping.java:568)
    at org.eclipse.persistence.internal.queries.MappedKeyMapContainerPolicy.getKeyMappingDataForWriteQuery(MappedKeyMapContainerPolicy.java:145)
    at org.eclipse.persistence.mappings.OneToManyMapping.updateTargetRowPostInsertSource(OneToManyMapping.java:1425)
    at org.eclipse.persistence.mappings.OneToManyMapping.performDataModificationEvent(OneToManyMapping.java:936)
    at org.eclipse.persistence.internal.sessions.CommitManager.commitAllObjectsWithChangeSet(CommitManager.java:162)
    at org.eclipse.persistence.internal.sessions.AbstractSession.writeAllObjectsWithChangeSet(AbstractSession.java:4387)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabase(UnitOfWorkImpl.java:1493)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabaseWithChangeSet(UnitOfWorkImpl.java:1583)
    at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.issueSQLbeforeCompletion(UnitOfWorkImpl.java:3258)
    at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.issueSQLbeforeCompletion(RepeatableWriteUnitOfWork.java:357)
    at org.eclipse.persistence.transaction.AbstractSynchronizationListener.beforeCompletion(AbstractSynchronizationListener.java:160)
    at org.eclipse.persistence.transaction.JTASynchronizationListener.beforeCompletion(JTASynchronizationListener.java:70)
    at com.sun.enterprise.transaction.JavaEETransactionImpl.commit(JavaEETransactionImpl.java:452)
    ... 94 more

其他有相同错误的问题建议在枚举类型的属性上添加@Enumerated(EnumType.STRING)，我在手机地图上使用了@MapKeyEnumerated(EnumType.STRING)，但我仍然看到这个错误。任何线索我错在哪里？

如果我没有按照 SO 指导提出问题，请告诉我，我会更正它（因为这是我的第一个问题）。

【问题讨论】：

标签： jax-rs eclipselink jpa-2.0 payara java-ee-8

【解决方案1】：

我对@987654321@ 类进行了如下更改

@Entity
@Table(name = "phone_number")
public class PhoneNumber extends BaseEntity {

  private PhoneType type;
  private String areaCode;
  private String number;

  //... default constructor, getters and setters
}

然后在UserAccount 中添加@MapKey(name = "type")，如下所示。

@OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "useraccount_id")
    @MapKeyEnumerated(EnumType.STRING)
    @MapKey(name = "type")
    private Map<PhoneType, PhoneNumber> phones = new HashMap<PhoneType, PhoneNumber>();

通过这些更改，我现在能够成功地将 UserAccount 对象保存到 db 表中。

【讨论】：