“cannot simultaneously fetch multiple bags”的解決方法

Java代碼

@OneToMany(mappedBy = "customer",cascade = {CascadeType.ALL},fetch = FetchType.LAZY)        
private Collection<CartItem> cartItems;        
                
@OneToMany(mappedBy = "customer",cascade = {CascadeType.ALL},fetch = FetchType.EAGER)        
private Collection<BookOrder> orders ;        

 

在用JPA進行註釋時，如果一個實體裏要映射多個集合實體時，我們不能把兩個集合的的FetchType設置爲EAGER,此時只能設置爲LAZY,否則會報：cannot simultaneously fetch multiple bags。或者我們也可以藉助:@IndexColumn