JPA2：我使用的是JoinColumn作爲queryparam創建查詢和異常發生，爲什麼

Question

@JoinColumn(name = "want_uid", referencedColumnName = "id") 
    @ManyToOne 
    private BookUsers wantUid; 
    @JoinColumn(name = "sale_uid", referencedColumnName = "id") 
    @ManyToOne 
    private BookUsers saleUid; 
    @JoinColumn(name = "book_id", referencedColumnName = "id") 

這個代碼是從實體bean 和我寫使用want_uid作爲queryparam。作爲fllows查詢：

BookUsers bookUsers=userDA.findUserByID(wantID); 
Query query= em.createQuery("SELECT b FROM BookOrder b WHERE b.want_uid = :want_uid"); 
query.setParameter("want_uid", bookUsers); 

一個異常：

javax.servlet.ServletException: java.lang.IllegalArgumentException: An exception occurred while creating a query in EntityManager: 
Exception Description: Error compiling the query [SELECT b FROM BookOrder b WHERE b.want_uid = :want_uid], line 1, column 34: unknown state or association field [want_uid] of class [com.xbook.entities.BookOrder]. 

我沒有找到原因... 你能告訴我嗎？ 感謝

Answer 1

在查詢

b.want_uid 

需要改變，以

b.wantUid 

所以，

SELECT b FROM BookOrder b WHERE b.wantUid = :want_uid