Hibernate / JPA - >可以为空的值&对象？ [英] Hibernate / JPA -> Nullable values & objects?
问题描述
我的基本问题是：我如何强迫Hibernate分别使float为NULLable和接受NULL为NULL，datetime，blob？我的意思是NULL，而不是（float）0.0。更糟的是，当我尝试存储一个实际为NULL并使用实体管理器的期望的NULLable字段的对象时，我获得属性的错误，即使在db表中，也被Hibernate标记为NULLable。
这是我一直徒劳的尝试：
考虑下表：
+ -------- + ---- ---------- + ------ + ------ + --------- + ---------------- +
|字段|类型|空| Key |默认|额外|
+ -------- + -------------- + ------ + ----- + -------- - + ---------------- +
| id | int（11）| NO | PRI | NULL | auto_increment |
|名称| varchar（255）| NO | | NULL | |
|数字| float |是| | NULL | |
| url | varchar（3）|是| | NULL | |
| mydate |日期|是| | NULL | |
+ -------- + -------------- + ------ + ----- + -------- - + ---------------- +
这是由这些语句创建：
DROP SCHEMA如果存在`mydb`;
如果不存在CREATE SCHEMA`mydb`默认字符集utf8 COLLATE utf8_unicode_ci;
USE`mydb`;
DROP TABLE如果存在`mydb`.`test`;
CREATE TABLE IF NOT EXISTS`mydb`.`test`（
`id` INT NOT NULL AUTO_INCREMENT，
`name` VARCHAR（255）NOT NULL，
`number` FLOAT NULL，
`url` VARCHAR（3）NULL，
`mydate` DATE NULL，
PRIMARY KEY（`id`），
UNIQUE INDEX`id_UNIQUE`（`id `ASC））
ENGINE = InnoDB;
如果我执行以下插入操作：
INSERT INTO`mydb`.`test`（`name`）VALUES（'MyName'）;
SELECT * FROM`mydb`.`test`;
我得到以下结果：
+ ---- + -------- + -------- + ------ + -------- +
| id |名称|数字| url | mydate |
+ ---- + -------- + -------- + ------ + -------- +
| 1 | MyName | NULL | NULL | NULL |
+ ---- + -------- + -------- + ------ + -------- +
1行（0.00秒）
这正是我想要的。
使用Hibernate 3.5 / JPA2，我尝试像这样做我的ORM：
BO：
public class BodyStat extends BusinessObject {
@Id
private int id;
私人字符串名称;
@Column（nullable = true）
私人浮动数字;
@Column（nullable = true）
私人网址;
@Column（nullable = true）
私人日期myDate;
... C'Tor / setters / getters / eof
和我的orm.xml中的实体看起来像这样：
< entity class =test>
< table name =& quot; test& quot;/>
<属性>
< id name =id>
< generated-value strategy =TABLE/>
< / id>
< basic name =name/>
< basic name =numberoptional =true/>
< basic name =urloptional =true/>
< basic name =myDateoptional =true/>
< / attributes>
< / entity>
现在Hibernate生成的表如下所示：
+ -------- + -------------- + ------ + ----- + --------- + ------------ +
|字段|类型|空| Key |默认|额外|
+ -------- + -------------- + ------ + ----- + -------- - + ------------ +
| id | int（11）| NO | PRI | NULL | |
|名称| varchar（255）| NO | | NULL | |
|数字| float | NO | | NULL | |
| url | tinyblob |是| | NULL | |
| mydate |日期|是| | NULL | |
+ -------- + -------------- + ------ + ----- + -------- - + ------------ +
这不完全是我想。正如你所看到的那样，
- float不为空，
- 类型url作为blob而不是varchar，并且
- mydate作为date而不是datetime
解决方案再次感谢您的大力支持和建议。其实，我现在已经找到了解决方案。正如帕斯卡所说，我一直在使用注解驱动和xml配置。
我不会在hibernate上打开一个bug，因为无论如何不要混淆配置类型，因此，我宁愿给出建议来进行最佳实践，而不是混淆配置类型。
干杯
ERMy basic question is: How can I force Hibernate to make float NULLable and accept NULL for float, datetime, blob, respectively? I really mean NULL, not (float) 0.0.
Even worse, when I try to store an object with the desired NULLable fields actually being NULL and using entity manager, I get errors for attributes, which are marked as NULLable by Hibernate even in the db table.
Here is what I have been trying in vain:
Consider this table:
+--------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(255) | NO | | NULL | | | number | float | YES | | NULL | | | url | varchar(3) | YES | | NULL | | | mydate | date | YES | | NULL | | +--------+--------------+------+-----+---------+----------------+which was created by these statements:
DROP SCHEMA IF EXISTS `mydb` ; CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET utf8 COLLATE utf8_unicode_ci ; USE `mydb` ; DROP TABLE IF EXISTS `mydb`.`test` ; CREATE TABLE IF NOT EXISTS `mydb`.`test` ( `id` INT NOT NULL AUTO_INCREMENT , `name` VARCHAR(255) NOT NULL , `number` FLOAT NULL, `url` VARCHAR(3) NULL , `mydate` DATE NULL , PRIMARY KEY (`id`) , UNIQUE INDEX `id_UNIQUE` (`id` ASC) ) ENGINE = InnoDB;If I carry out following insert:
INSERT INTO `mydb`.`test` (`name`) VALUES ('MyName'); SELECT * FROM `mydb`.`test`;I get following result:
+----+--------+--------+------+--------+ | id | name | number | url | mydate | +----+--------+--------+------+--------+ | 1 | MyName | NULL | NULL | NULL | +----+--------+--------+------+--------+ 1 row in set (0.00 sec)which is exactly what I want.
With Hibernate 3.5 / JPA2, I try do do my ORM like this:
BO:
public class BodyStat extends BusinessObject { @Id private int id; private String name; @Column(nullable = true) private float number; @Column(nullable = true) private URL url; @Column(nullable = true) private Date myDate; ... C'Tor / setters / getters / eofand the entity in my orm.xml looks like this:
<entity class="test"> <table name=""test""/> <attributes> <id name="id"> <generated-value strategy="TABLE"/> </id> <basic name="name"/> <basic name="number" optional="true"/> <basic name="url" optional="true"/> <basic name="myDate" optional="true"/> </attributes> </entity>Now the table generated by Hibernate looks like this:
+--------+--------------+------+-----+---------+------------+ | Field | Type | Null | Key | Default | Extra | +--------+--------------+------+-----+---------+------------+ | id | int(11) | NO | PRI | NULL | | | name | varchar(255) | NO | | NULL | | | number | float | NO | | NULL | | | url | tinyblob | YES | | NULL | | | mydate | date | YES | | NULL | | +--------+--------------+------+-----+---------+------------+which is not quite what I want. As you can see
- float is not nullable,
- the type "url" turned out to as a blob rather than a varchar and
- mydate as "date" rather than "datetime"
解决方案Again thanks for your great support and suggestions. Actually, I have found the solution now. As Pascal mentioned, I had been using both, annotation driven and xml configuration mixed up. As soon as I deleted the xml config, this issue was solved.
I will not open an bug at hibernate, because it is best practice anyway not to mix up configuration types, hence, I would rather give the advice to carry out best practice than to mix up config types.
Cheers ER
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- 类型url作为blob而不是varchar，并且
