如何在hbm.xml文件的hibernate中創建復合主鍵

Question

我有以下三個簡單的類。 如何在我的Rating.hbm.xml文件中映射Rating類，尤其是其組合鍵？ 我目前在休眠文檔（5.1.2.1。復合標識符）中迷路了

每個評分可以有一本書，一個用戶可以進行特定評分。 每個用戶可以進行許多評級。 每本書可以有很多等級。

班級

等級等級

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

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

用戶類別

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

書本類

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

    public Book() {}
    ...
}

Answer 1

首先，您應該創建一個這樣的復合主鍵類：

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 */ 


}

現在，像這樣創建您的主要Rating類：

public class RatingBook {
RatingId RatingId;
private Date timestamp;

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

}

您可以嘗試以下方法：

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

看看是否適合您