将枚举映射到具有Hibernate注释的表

冬眠有点可怕。这是一个很好的ORM的一个奇怪的失败。绕过它的“最简单”方法是将枚举声明为自定义的休眠类型。幸运的是,Hibernate编写了一个示例实现,您可以在应用程序中逐字输入:

http://www.hibernate.org/265.html

它们甚至包括如何使用它的说明。这是我在需要持久枚举时使用的模式。

我创建了一个类似的类,比如Hibernate建议的类,它是可配置的,不需要为这个持久性创建一个新的类型。

可以像这样使用

@Type(type = "ro.raisercostin.hibernate.EnumUserType", parameters = @Parameter(name = "type", value = "DealType"))
DealType dealType;

我添加了一个参数化类型的实现来支持传递的参数。

public class EnumUserType implements UserType, ParameterizedType {

    private static final int[] SQL_TYPES = { Types.VARCHAR };
    private Class clazz = null;

    public EnumUserType() {
    }

    @Override
    public void setParameterValues(Properties parameters) {
        String className = (String) parameters.get("type");
        try {
            this.clazz = Class.forName(className);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("Couldn't get the class for name [" + className + "].", e);
        }
    }

    public int[] sqlTypes() {
        return SQL_TYPES;
    }

    public Class returnedClass() {
        return clazz;
    }

    public Object nullSafeGet(ResultSet resultSet, String[] names, Object owner) throws HibernateException,
            SQLException {
        String name = resultSet.getString(names[0]);
        Object result = null;
        if (!resultSet.wasNull()) {
            result = Enum.valueOf(clazz, name);
        }
        return result;
    }

    public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index) throws HibernateException,
            SQLException {
        if (null == value) {
            preparedStatement.setNull(index, Types.VARCHAR);
        } else {
            preparedStatement.setString(index, ((Enum) value).name());
        }
    }

    public Object deepCopy(Object value) throws HibernateException {
        return value;
    }

    public boolean isMutable() {
        return false;
    }

    public Object assemble(Serializable cached, Object owner) throws HibernateException {
        return cached;
    }

    public Serializable disassemble(Object value) throws HibernateException {
        return (Serializable) value;
    }

    public Object replace(Object original, Object target, Object owner) throws HibernateException {
        return original;
    }

    public int hashCode(Object x) throws HibernateException {
        return x.hashCode();
    }

    public boolean equals(Object x, Object y) throws HibernateException {
        if (x == y) {
            return true;
        }
        if ((null == x) || (null == y)) {
            return false;
        }
        return x.equals(y);
    }
}

可以用注释枚举 @Entity 并使用custoumn元组创建枚举的实例 Enum.valueOf

然后,枚举声明如下所示:

@Entity
@Table(name = "node_interface_type")
@Tuplizer(impl = EnumTuplizer.class)
public enum Type {
    WIRED, WIRELESS, WIRELESS_SENSOR_NODE;
    @Id
    public String name = toString();
}

Tuplezer是:

public class EnumTuplizer extends PojoEntityTuplizer {
    public EnumTuplizer(EntityMetamodel entityMetamodel, PersistentClass mappedEntity) {
        super(entityMetamodel, mappedEntity);
    }

    @Override
    protected Instantiator buildInstantiator(final PersistentClass persistentClass) {
        return new Instantiator() {
            @Override
            public Object instantiate(Serializable id) {
                try {
                    return Enum.valueOf(
                            (Class) persistentClass.getClass().getClassLoader().loadClass(persistentClass.getClassName()),
                            (String) id
                    );
                } catch (ClassNotFoundException e) {
                    throw new AssertionError(e);
                }
            }

            @Override
            public Object instantiate() {
                throw new UnsupportedOperationException();
            }

            @Override
            public boolean isInstance(Object object) {
                throw new UnsupportedOperationException();
            }
        };
    }
}

如果只想以只读方式使用实体,则可以使用 @Formula 和 @Enumerated . 尝试以下方法:

@Entity
public class Deal {
   @Formula("(select text from DEAL_TYPE dt where dt.id = typeId)")
   @Enumerated(EnumType.STRING)
   DealType type;
}

虽然远不是理想的,但我解决这个问题的方法是使用EnumStringType和非规范化的可更新视图。