@GenerateValue(strategy = GenerationType.AUTO) 没有按预期工作
我正在尝试将对象持久保存到数据库中。不断收到“列 ID 无法接受空值错误”。我的对象看起来像这样：
@Entity
public class TestTable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id = 0;
@Column(nullable=false, length=256)
private String data = "";
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getData() {
return data;
}
public void setData(String data) {
this.data = data;
}
}
我的持久函数：
public static synchronized boolean persistObject(Object obj){
boolean success = true;
EntityManager em = null;
EntityTransaction tx = null;
try{
em = getEmf().createEntityManager();
tx = em.getTransaction();
tx.begin();
em.persist(obj);
tx.commit();
} catch (Exception e){
success = false;
} finally{
try{
em.close();
} catch(Exception e){
//nothing
}
}
return success;
}
I'm trying to persist an object to a database. Keep getting 'Column ID cannot accept null value error'. My object looks like this:
@Entity
public class TestTable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Integer id = 0;
@Column(nullable=false, length=256)
private String data = "";
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getData() {
return data;
}
public void setData(String data) {
this.data = data;
}
}
My persist function:
public static synchronized boolean persistObject(Object obj){
boolean success = true;
EntityManager em = null;
EntityTransaction tx = null;
try{
em = getEmf().createEntityManager();
tx = em.getTransaction();
tx.begin();
em.persist(obj);
tx.commit();
} catch (Exception e){
success = false;
} finally{
try{
em.close();
} catch(Exception e){
//nothing
}
}
return success;
}
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评论（7）
您可以使用 GenerationType.TABLE。
这样，jpa 使用序列表进行 id 分配，您可能永远不需要生成序列或自动增量值或降低可移植性的触发器。
另请注意，在 java 中 int 类型默认以 0 启动，因此您也可以摆脱它。
You may use GenerationType.TABLE.
That way, jpa uses a sequence table for id assigment and you may never need to generate sequence or auto-increment values or triggers that lowers portability.
Also note that in java int type is initiated with 0 default, so you may get rid of that also.
就我而言，
这是关于错误的方言：而不是
当我切换到生产数据库时， ：。 Hibernate 尝试使用为不同数据库引擎准备的策略。
In my case it was about bad dialect:
instead of:
when I switched to the production database. Hibernate tried to use strategy prepared for different db engine.
我遇到了与你类似的问题。我最终发现我的数据库连接的配置是错误的：我连接到一个具有不正确架构的旧数据库。新架构将主键列声明为
所以 数据库本身自动生成主键，而旧模式将其声明为
Hibernate 为新模式执行了正确的代码，但在旧模式上失败了，因为旧模式要求 SQL
INSERT为INSERT提供一个值代码>ID列。I had a problem with a similar manifestation to yours. I eventually discovered that the configuration of my database connection was wrong: I was connecting to an old database that had an incorrect schema. The new schema declared the primary-key column as
so the database itself automatically generated the primary key whereas the old schema declared it as
Hibernate executed the correct code for the new schema, which failed on the old schema because the old schema demanded the SQL
INSERTprovide a value for theIDcolumn.以防万一有人遇到与我相同的问题。我已经为此苦苦挣扎了几个小时，只想发布我的解决方案。看起来 ID 总是设置为 0，这会引发错误。
模型中的 id 属性必须是“Long”或“Integer”类型，而不是“long”或“integer”类型（注意大小写）。我输入了“long”，它是一个原始类型，不能为空。因此默认值为 0，Hibernate 没有意识到它是一个新实体，并尝试使用 ID = 0 来保存它，这显然不起作用。
将其更改为引用类型“Long”（可以为空），解决了它。
Just in case someone arrives at this thread with the same problem as me. I have been struggling with this for some hours now, and just want to post my solution. It seemed the ID was always set to 0, and that threw an error.
The id property in the model must be of type "Long" or "Integer" and not "long" or "integer" (notice the capitalization). I had put "long", which is a primitive type and cannot be null. Therefore the default value was 0 and Hibernate didn't realize that it was a new entity and tried to save it with ID = 0, something that obviously did not work.
Changing this into the reference type "Long", which can be null, solved it.
或者尝试使用 @GenerateValue(strategy = GenerationType.AUTO)
而不是@GenerateValue(strategy = GenerationType.SEQUENCE)。
Or try with
@GeneratedValue(strategy = GenerationType.AUTO)instead of
@GeneratedValue(strategy = GenerationType.SEQUENCE).当 ID 列是 Int 时，Hibernate 以无声且神秘的方式失败。尝试在代码中将其更改为 Long，并在数据库中将其更改为无符号 64 位整数。这为我解决了这个问题。
Hibernate fails in silent and mysterious ways when the ID column is an Int. Try changing it to Long in the code and an unsigned 64-bit integer in the database. That fixed the issue for me.
我正在努力解决同样的问题，不知何故，我需要长时间工作而不是长类型:)。作为解决方法，我将数据库中的 id 列转换为 SERIEL。我正在使用 postgres 数据库。
I was struggling with the same problem and somehow for me long work instead of LONG type :). As a workarround I converted id column in database as SERIEL. I am using postgres db.