如何從衆多獲取對象一個關係，通過一些財產

Question

我有兩個實體：

@Entity 
public class FuturePlan { 
    @Id 
    @GeneratedValue(strategy=GenerationType.IDENTITY) 
    private int fpId; 
    private String about; 
    private Date travelDate; 
    @ManyToOne(fetch=FetchType.LAZY) 
    private User user; 
    @ManyToOne(fetch=FetchType.LAZY) 
    private Location location; 

    ....contructors and get/set 

...和

@Entity 
public class Location { 
    @Id 
    @GeneratedValue(strategy=GenerationType.IDENTITY) 
    private int lId; 
    private String lName; 
    ....contructors and get/set 

如何到location.name == "Something"得到所有futurePlan實例？

Answer 1

1.You可以很好地使用本地查詢類似下面：

String q="select * from employer employer,employee where employer.id= 
        employee.employerId and employee.location='xyz'"; 
Query query= em.createNativeQuery(q,Object[].class); 
List<Object[]> students= query.getResultList(); 

也可以實現通過使用HQL以及相同的結果。

你也可以使用Criteria Query。