JPA/MySql問題

Question

我正在構建基於JPA的應用程序，使用mysql和ecliselink.I嘗試向我的數據庫中插入東西時出現了很奇怪的問題。我能夠將數據插入到單個表中，但是當涉及到一對一時，可能和反之亦然東西出錯。目前我有2個主要和1參考表（它擁有其他兩個表的外鍵）。這是奇怪的，因爲我沒有「序列」在我的數據庫表中當我嘗試插入數據到任何我的表，我得到這個異常：

[EL Info]: 2012-03-15 17:52:28.64--ServerSession(18621340)--EclipseLink, version: Eclipse Persistence Services - 2.3.2.v20111125-r10461 
[EL Info]: 2012-03-15 17:52:29.23--ServerSession(18621340)--file:/D:/git-eclipse/Martin/reference/build/classes/_reference login successful 
[EL Warning]: 2012-03-15 17:52:29.389--ClientSession(31843177)--Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException 
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'eclipse1.sequence' doesn't exist 
Error Code: 1146 
Call: UPDATE SEQUENCE SET SEQ_COUNT = SEQ_COUNT + ? WHERE SEQ_NAME = ? 
bind => [2 parameters bound] 
Query: DataModifyQuery(name="SEQUENCE" sql="UPDATE SEQUENCE SET SEQ_COUNT = SEQ_COUNT + ? WHERE SEQ_NAME = ?") 

Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Table 'eclipse1.sequence' doesn't exist 
Error Code: 1146 
Call: UPDATE SEQUENCE SET SEQ_COUNT = SEQ_COUNT + ? WHERE SEQ_NAME = ? 
bind => [2 parameters bound] 
Query: DataModifyQuery(name="SEQUENCE" sql="UPDATE SEQUENCE SET SEQ_COUNT = SEQ_COUNT + ? WHERE SEQ_NAME = ?") 
[EL Info]: 2012-03-15 17:52:29.394--ServerSession(18621340)--file:/D:/git-eclipse/Martin/reference/build/classes/_reference logout successful 
Exception in thread "main" java.lang.IllegalStateException: Attempting to execute an operation on a closed EntityManager. 
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.verifyOpen(EntityManagerImpl.java:1665) 
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.close(EntityManagerImpl.java:1529) 
at OneToManyRelation.main(OneToManyRelation.java:47) 

我張貼一類，只是因爲別人是非常相似的

@Entity 

    @Table(name="category") 

    public class Category { 

    @Id 
    @GeneratedValue(strategy=GenerationType.AUTO) 
    @Column(name="CategoryID") 
    private int CategoryID; 

/** 
* @return the id 
*/ 
public int getId() { 
return CategoryID; 
} 

/** 
* @param id the id to set 
*/ 
public void setId(int CategoryID) { 
this.CategoryID = CategoryID; 
} 

@Column(name="category", nullable=false, length=50, insertable=true) 
private String category; 

/** 
* @return the category 
*/ 
public String getCategory() { 
return category; 
} 


public void setCategory(String category) { 
this.category = category; 
} 

@OneToMany(cascade=CascadeType.ALL) 
@JoinTable(name = "templateemail", joinColumns = { 
@JoinColumn(name="categoryId", unique = true) 
}, 
inverseJoinColumns = { 
@JoinColumn(name="templateId") 
} 
) 
private Set<Template> template; 

/** 
* 
*/ 
public Set<Template> getChildren() { 
return template; 
} 

/** 
* 
*/ 
public void setChildren(Set<Template> template) { 
this.template = template; 
} 

} 

你知道我的代碼有什麼問題嗎？

在此先感謝

Answer 1

看到代碼將有助於發現它有什麼問題。但通過僅判斷錯誤消息，似乎您選擇使用序列或表生成器，並且此生成器依賴於（缺省情況下）名爲sequence的表，該表不存在於數據庫中。

創建此表，或將生成器配置爲使用現有表或更改ID生成器。