Question

My 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 / eof

and the entity in my orm.xml looks like this:

<entity class="test">
    <table name="&quot;test&quot;"/>
    <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

1. float is not nullable,
2. the type “url” turned out to as a blob rather than a varchar and
3. mydate as “date” rather than “datetime”

Answer 1

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