将多个属性映射到Hibernate中的单个列(UserType似乎不够)

Question

我们有很多表，它们的列定义如下：

create table tbl_1 (
id int primary key,
   -- ... a lot of specific stuff skipped
reserved_1 char (10), -- byte 1:   flag_A
                      -- byte 2-5: value_B
                      -- byte 6:   flag_C
                      -- byte 7-8: value_D
                      -- byte 9-10: not used 
                      --   flag_A, value_B, flag_C, value_D
                      --   have no relations to each other in general
reserved_2 char(10),  -- ....
);

我想将它映射到类，如下所示：

@Entity
@Table(name = "TBL_1", uniqueConstraints = @UniqueConstraint(columnNames = "ID"))
public class Tbl1 implements java.io.Serializable {
    private int id;
//  irrelevant properties skipped
    private String flagA;
    private String valueB;
    private String flagC;
    private String valueD;
// getters/setters will follow
}

在Hibernate中可能吗？据我所知，可以使用UserType将它们组合成单个列，如下所示(简化)：

public class Tbl1 implements java.io.Serializable {
   private int id;
//  irrelevant properties skipped
   private Reserved1 reserved1;
}

public class Reserved1 implements java.io.Serializable {
    private String flagA;
    private String valueB;
    private String flagC;
    private String valueD;
}

但我想隐藏所有对reserved1列/属性的引用，只为flagA、valueB、flagC和valueD宣传getters/setters，因为它们彼此无关，所以将它们组合到类中是一个糟糕的想法，并且为了保持将来(希望)表重组的灵活性。在Hibernate中可能吗？

Answer 1

好的，实际上这很简单:只需为fetch、update和insert定义自定义查询：

@SQLUpdate (sql = "UPDATE tbl_1 SET oth_col=?, reserved_1=(substring(?||' ' from 1 for 1) || substring(?||'    ' from 1 for 4) || substring(?||' ' from 1 for 1) || substring(?||'  ' from 1 for 2) where id=?")
@SQLInsert (sql = "define it the same way as update")
@Loader (namedQuery = "tbl_1_ldr")
@NamedNativeQuery (name="tbl_1_ldr", query="SELECT id,..., substring(reserved_1 from 1 for 1) as flag_a, substring(reserved_1 from 2 for 4) as value_b, substring(reserved_1 from 6 for 1) as flag_c, substring(reserved_1 from 7 for 2) as value_d FROM tbl_1 WHERE id = ? ")