[英]hibernate one-to-many save to database
我目前正在使用Hibernate
和Java
,正在嘗試將對象持久保存在數據庫中。 我們有一個Group
類和一個ToDoList
類。 Group
有一個一對多的關系ToDoList
作為顯示在此ERD 。
Group
類中的相關代碼:
@Entity
@Table(name = "Group", catalog = "db")
public class Group implements java.io.Serializable{
private int id;
private Set<ToDoList> allToDoLists;
public Group(){
allToDoLists = new HashSet<ToDoList>(0);
}
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "Group_id", unique = true, nullable = false)
public int getId(){
return this.id;
}
public void setId(int id){
this.id = id;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "group")
public Set<ToDoList> getAllToDoLists() {
return this.allToDoLists;
}
public void addTodoList(ToDoList t){
this.allToDoLists.add(t);
t.setGroup(this);
}
public void setAllToDoLists(Set<ToDoList> allToDoLists) {
this.allToDoLists = allToDoLists;
}
}
ToDoList
類的相關代碼:
@Entity
@Table (name = "Todo_List", catalog = "db")
public class ToDoList {
private int id;
private Group group;
public ToDoList(){}
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "Todo_List_id", unique = true, nullable = false)
public int getId(){
return this.id;
}
public void setId(int id) {
this.id = id;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "Group", nullable = false)
public Group getGroup() {
return this.group;
}
public void setGroup(Group group) {
this.group = group;
}
}
發生問題的代碼:
ToDoList toDoList = new ToDoList("TodoList1","Iets","24-06-2015","24-06-2015");
Group group = new Group("Groep 1","10-11-2011","10-11-2011");
GroupDao groupDao = new GroupDaoImpl();
groupDao.store(group);
toDoList.setGroup(group);
toDoListDao.store(toDoList);
“ groupDao”和“ toDoListDao”中用於存儲的代碼基本相同:
Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
session.save(toDoList);
session.getTransaction().commit();
問題當我嘗試存儲ToDoList時,出現以下錯誤:
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Group, Name) values ('2015-06-24', '2015-06-24', 'Iets', 23, 'TodoList1')' at line 1
需要如果可以存儲Group
和ToDoList
也最好將其保存。 鑒於我們即將到來的截止日期,如果我可以自己存儲Group
和ToDoList
,誰也足夠了
“ Group”是一個SQL關鍵字(“ group by”)。 因此,這不是表名的最佳選擇。 鑒於Hibernate生成了DBMS不接受的SQL,這似乎引起了沖突。
如果您不能更改表名,則可以通過引用實體中的名稱來解決該沖突,如下所示:
@Table(name = "`Group`", catalog = "db")
要么
@Table(name = "\"Group\"", catalog = "db")
編輯:
就像ug_告訴我的那樣,您還可以在persistence.xml文件中設置以下hibernate屬性,以默認情況下對所有標識符執行此操作:
<property name="hibernate.globally_quoted_identifiers" value="true" />
我自己從未使用過它,但是Javadocs確認這確實是受支持的屬性:
https://docs.jboss.org/hibernate/orm/4.2/javadocs/org/hibernate/cfg/AvailableSettings.html
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