为什么休眠OneToMany @BatchSize不起作用？ [英] why hibernate OneToMany @BatchSize is not working?

问题描述

我使用spring 4.1.4.RELEASE + hibernate 4.3.6.Final，我正在尝试@BatchSize for OneToMany，但它看起来不起作用，下面是代码：

$ b $创建表产品（
id int（6）unsigned auto_increment主键，
name varchar（30）
）; b

  
 
创建表格图片（
 id int（6）unsigned auto_increment主键，
 product_id varchar（30），$ b $ url url varchar（30）
） ; 
 
 @Entity（name =product）
 public class Product extends BaseEntity {
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name =id）
 private int id; 
 
 @Column（name =name）
私有字符串名称; 
 
 @OneToMany（fetch = FetchType.LAZY，mappedBy =product）
 @BatchSize（size = 2）
 private List< Picture>图片; 
 
公开列表<图片> getPictures（）{
返回图片; 
} 
 
 public void setPictures（List< Picture> pictures）{
 this.pictures = pictures; 
 
 
 
 $ b @Entity（name =picture）
 @BatchSize（size = 10）
 public class图片扩展BaseEntity {
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 @Column（name =id）
 private int id; 
 
 @Column（name =url）
 private String url; 
 $ b @ManyToOne（fetch = FetchType.LAZY）
 @JoinColumn（name =product_id，referencedColumnName =id）
 private Product product; 
 
 public Product getProduct（）{
 return product; 
} 
 
 public void setProduct（Product product）{
 this.product = product; 
} 
} 
 
 
 @Repository 
 public class ProductDao extends AbstractHibernateDao< Product>执行IProductDao {
 
 public ProductDao（）{
 super（）; 
 setClazz（Product.class）; 
} 
 
 @Override 
 public Product find（final int id）{
 Product product =（Product）getCurrentSession（）。get（clazz，id）; 
 System.out.println（* -------------------- find ----------------- --------）; 
 System.out.println（product.getPictures（））; 
 System.out.println（* -------------------- end ----------------- --------）; 
 
退货产品; 
 
 
 $ / code> 

我试图通过id来查找产品，但是该产品里面没有任何图片，我试图把BatchSize放在getPictures上面，但它仍然不起作用。

我想知道是否我错过了一些配置什么的，任何人都可以提供帮助？

更新：

以下是日志：

$ b

  [DEBUG] 2016-10-03 17:20：57.074 RequestMappingHandlerMapping：getHandlerInternal [302]：返回处理程序方法[public com.lehoolive.analyse.model .REesponse com.lehoolive.analyse.controller.ProductController.detail（int）] 
 [DEBUG] 2016-10-03 17:20：57.075 DispatcherServlet：doDispatch [931]：Last-Modified value for [/ product / detail / 1]为：-1 
 Hibernate：选择product0_.id作为id2_0_，product0_.name作为name2_0_ from product product0_ where product0_.id =？ 
 * -------------------- find ------------------------ -  
 Hibernate：选择pictures0_.product_id作为product3_2_1_，pictures0_.id作为id1_，pictures0_.id作为id1_0_，pictures0_.product_id作为product3_1_0_，pictures0_.url作为url1_0_从图片pictures0_ where pictures0_.product_id =？ 
 [com.lehoolive.analyse.entity.Picture@29a0ce34，com.lehoolive.analyse.entity.Picture@5a7a10d8，com.lehoolive.analyse.entity.Picture@3e80350] 
 * ---- ----------------结束------------------------- 
 [DEBUG] 2016 -10-03 17：20：57.333 ResponseBodyAdviceChain：invoke [61]：为body = com.lehoolive.analyse.model.Response@59141f65调用ResponseBodyAdvice链
  

解决方案

（来自评论）

默认情况下无法识别JPA认为getPictures（）返回有限数量的图片（afaik）。一般来说，我不认为你可以限制返回的连接对象的数量。

如果您想限制 find 方法返回的图片数量，您必须编写自己的方法（ @BatchSize 仅限制 SELECTS 语句的数量，而不是结果数量）。

您可以使用JPA完成此操作：在图片（而非产品）上创建JPQL查询，然后添加 .setMaxResult（2） .getResults（）（你可以用 youPicturesList（）。get（0）.getProduct（） code $）



也许你可以用 CriteriaBuilder 来做你想做的事，这可能会限制你在加入entites，但我从来没有像这样使用它。

I am using spring 4.1.4.RELEASE + hibernate 4.3.6.Final, I am trying @BatchSize for OneToMany, but it seems not working, here is the code:

create table product (
    id int(6) unsigned auto_increment primary key,
    name varchar(30)
);

create table picture (
    id int(6) unsigned auto_increment primary key,
    product_id varchar(30),
    url varchar(30)
);

@Entity(name = "product")
public class Product extends BaseEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;

    @Column(name = "name")
    private String name;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "product")
    @BatchSize(size=2)
    private List<Picture> pictures;

    public List<Picture> getPictures() {
        return pictures;
    }

    public void setPictures(List<Picture> pictures) {
        this.pictures = pictures;
    }
}


@Entity(name = "picture")
@BatchSize(size=10)
public class Picture extends BaseEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;

    @Column(name = "url")
    private String url;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "product_id", referencedColumnName = "id")
    private Product product;

    public Product getProduct() {
        return product;
    }

    public void setProduct(Product product) {
        this.product = product;
    }
}


@Repository
public class ProductDao extends AbstractHibernateDao<Product> implements IProductDao {

    public ProductDao() {
        super();
        setClazz(Product.class);
    }

    @Override
    public Product find(final int id) {
        Product product = (Product) getCurrentSession().get(clazz, id);
System.out.println("*--------------------find-------------------------");
System.out.println(product.getPictures());
System.out.println("*--------------------end-------------------------");

        return product;
    }
}

I tried to find Product by id, however the product doesn't contain any pictures inside, I tried to put the BatchSize above the getPictures as well, but it still doesn't work.

I am wondering if I missed some configuration or something, could anyone help?

UPDATE:

Here is the log:

[DEBUG] 2016-10-03 17:20:57.074 RequestMappingHandlerMapping:getHandlerInternal[302]: Returning handler method [public com.lehoolive.analyse.model.IResponse com.lehoolive.analyse.controller.ProductController.detail(int)]
[DEBUG] 2016-10-03 17:20:57.075 DispatcherServlet:doDispatch[931]: Last-Modified value for [/product/detail/1] is: -1
Hibernate: select product0_.id as id2_0_, product0_.name as name2_0_ from product product0_ where product0_.id=?
*--------------------find-------------------------
Hibernate: select pictures0_.product_id as product3_2_1_, pictures0_.id as id1_, pictures0_.id as id1_0_, pictures0_.product_id as product3_1_0_, pictures0_.url as url1_0_ from picture pictures0_ where pictures0_.product_id=?
[com.lehoolive.analyse.entity.Picture@29a0ce34, com.lehoolive.analyse.entity.Picture@5a7a10d8, com.lehoolive.analyse.entity.Picture@3e80350]
*--------------------end-------------------------
[DEBUG] 2016-10-03 17:20:57.333 ResponseBodyAdviceChain:invoke[61]: Invoking ResponseBodyAdvice chain for body=com.lehoolive.analyse.model.Response@59141f65

解决方案

(From the comments)

There is no way to tell by default JPA that the getPictures() return a limited number of pictures (afaik). In general, I don't think you can limit the number of joined objects returned.

If you want to limit the number of pictures returned by the find method, you have to write your own method (@BatchSize only limits the number of SELECTS statements made, not the number of result).

You can do this with JPA: create a JPQL query on Pictures (not Product), then add .setMaxResult(2) before .getResults() (and you can get your product with youPicturesList().get(0).getProduct(); )

Maybe you can do what you want with the CriteriaBuilder which may allow you to limit on joined entites, but I've never used it like this.

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