如何将java.lang.Object类型字段保留在可嵌入类中

Question

我有一个这样的实体：

@Entity(name = "A")
public class A implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    private String A_Id;

    private String field1;

    private String field2;

    @ElementCollection
    @CollectionTable(name = "B", joinColumns = @JoinColumn(name = "A_Id"))
    private Set<B> b;

    // getters and setters
}

@Embeddable
public class B implements Serializable {

    private static final long serialVersionUID = 1L;

    private String name;

    @Column(name = "VALUE", length = 255, columnDefinition = "TEXT")
    @Convert(converter = ObjectConverter.class)
    private Object value;

    // getters and setters
}

转换器类如下所示：

@Converter(autoApply = true)
public class ObjectConverter implements AttributeConverter<Object, String> {

    private static String getType(Object obj) {
        if (obj instanceof Boolean) {
            return "b";
        } else if (obj instanceof Integer || obj instanceof Long) {
            return "i";
        } else if (obj instanceof Double || obj instanceof Float) {
            return "d";
        } else if (obj instanceof String) {
            return "s";
        }
    }

    public String convertToDatabaseColumn(Object anyType) {

        if (anyType == null) {
            return null;
        }

        return String.format("%s:%s", getTypeCode(anyType), anyType.toString());
    }

    public Object convertToEntityAttribute(String encoded) {

        if (encoded == null) {
            return null;
        }

        final String val = encoded.substring(2);

        switch (encoded.charAt(0)) {
            case 'b':
                return Boolean.parseBoolean(val);
            case 'i':
                return Long.parseLong(val);
            case 'd':
                return Double.parseDouble(val);
            case 's':
                return val;
            default:
                throw new IllegalArgumentException("Unexpected encoded string: " + encoded);
        }

    }

}

现在我从Hibernate中得到一个异常，像这样：

  

org.hibernate.MappingException：集合元素映射的列数错误：B类型：component [name，value]

但是，如果我不将java.lang.Object字段保留在嵌入式类中，而是将其保留在主实体中，则它可以正常工作。

例如，这很好用：

@Entity(name = "A")
public class A implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    private String A_Id;

    private String field1;

    private String field2;

    @Column(name = "VALUE", length = 255, columnDefinition = "TEXT")
    @Convert(converter = ObjectConverter.class)
    private Object value;

    // getters and setters
}

如何将Object字段保留在可嵌入类中，并使用Hibernate和JPA进行存储？