hibernate多表联合查询

痛定思痛。 2022-09-22 11:59 292阅读 0赞

//三表联合查询  
/\*  
\* select t.\* from product t,category c,categorysecond cs  
WHERE t.csid = cs.csid  
and c.cid = cs.cid  
and c.cid = 1  
\*/  
/\*  
\* 如果是写HQL语句的写法  
\*  
\* select p from Category c ,CategorySecond cs ,Product p where c.cid = cs.category.cid  
\* and cs.csid = p.categorySecond.csid  
\* and c.cid = ?  
\*  
\*/

//hibernate自动外键关联，可以简化代码，提高效率  
String hql = “select p from Product p join p.categorySecond cs join cs.category c where c.cid = ?”;

//这个是多表联合查询，因此不能使用离线查询  
List\\<\\Product> list = this.getHibernateTemplate().execute(new PageHibernateCallback\\<\\Product>(hql, new Object\[\]\{cid\}, begin, limit));

——————————-java类

public class Product \{

private Integer pid;
    
    private String pname;
    
    private Double market_price;
    
    private Double shop_price;
    
    private String image;
    
    private String pdesc;
    
    private Integer is_hot;
    
    private Date pdate;
    
    //二级分类因为是外键hibernate只能创建对象
    private CategorySecond categorySecond;
    
    set,get方法..................

public class CategorySecond \{

private Integer csid;
    
    private String csname;
    
    /*一级分类的外键*/
    private Category category;
    
    //配置商品的集合
    private Set<Product> products = new HashSet<>();
    
    
    set,get方法..................

—————————————–hbm配置文件

!DOCTYPE hibernate-mapping PUBLIC  
“-//Hibernate/Hibernate Mapping DTD 3.0//EN”  
“[http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd][http_www.hibernate.org_dtd_hibernate-mapping-3.0.dtd]“>

[http_www.hibernate.org_dtd_hibernate-mapping-3.0.dtd]: http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd