Question

我有以下三个简单的类。如何在Rating.hbm.xml文件中映射Rating类，更具体地说是它的复合键？我目前在hibernate文档（5.1.2.1。复合标识符）

中迷失了方向

每个评级可以有一本书和一个用户进行特定评级。每个用户都可以进行很多评级。每本书都有很多评分。

类

评级等级

    public class Rating {
        private User user;
        private Book book;
        private int rating;
        private Date timestamp;

        public Rating() {}  //No arg contructor for hibernate
    ... 
}

用户类

public class User {
    private long userId;
    private String email, password;
    public User() {}
    ...
}

预订课程

public class Book {
    private long bookId;
    private String title;

    public Book() {}
    ...
}

Answer 1

首先，您应该创建一个复合主键类，如下所示：

public class RatingId implements Serializable{
private User user;
private Book book;
private int rating;
// an easy initializing constructor
public PurchasedTestId(User user, Book book, int rating){
this.user = user;
this.book = book;
this.rating= rating;
}

/*create your getter and setters plus override the equals and hashCode()  methods */ 


}

现在创建您的主要评级类：

public class RatingBook {
RatingId RatingId;
private Date timestamp;

/* generate getters and setters for these two methods*/

}

您可以尝试以下方法：

<composite-id name=”ratingId”>
<key-property name="user" column="user"  />
<key-property name="book" column="book" />
<key-property name="rating" column="pid" />
</composite-id>

并查看它是否适合您

如何在hbm.xml文件中的hibernate中创建复合主键

1 个答案: