Hibernate--批量抓取batch-size

以你之姓@ 2021-08-13 23:49 385阅读 0赞

#### 批量抓取 ####

在抓取策略中有一种叫做批量抓取，就是同时查询多个对象的关联对象的时候，可以采用批量抓取进行优化。

如果要实现批量抓取效果，可以通过batch-size来完成。

#### 创建表 ####

cst\_customer与cst\_linkman是一对多关系，cust\_id为外键。  
**cst\_customer表：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70]  
**cst\_linkman表：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70 1]

#### 创建实体类 ####

**Customer类：**

public class Customer { 
    	//主键
    	private Long cust_id;
    	
    	private String cust_name;
    	private String cust_source;
    	private String cust_industry;
    	private String cust_level;
    	private String cust_linkman;
    	private String cust_phone;
    	private String cust_mobile;
    	
    	//使用set集合,表达一对多关系
    	private Set<LinkMan> linkMens = new HashSet<LinkMan>();
    	
    	public Set<LinkMan> getLinkMens() { 
    		return linkMens;
    	}
    	public void setLinkMens(Set<LinkMan> linkMens) { 
    		this.linkMens = linkMens;
    	}
    	public Long getCust_id() { 
    		return cust_id;
    	}
    	public void setCust_id(Long cust_id) { 
    		this.cust_id = cust_id;
    	}
    	public String getCust_name() { 
    		return cust_name;
    	}
    	public void setCust_name(String cust_name) { 
    		this.cust_name = cust_name;
    	}
    	public String getCust_source() { 
    		return cust_source;
    	}
    	public void setCust_source(String cust_source) { 
    		this.cust_source = cust_source;
    	}
    	public String getCust_industry() { 
    		return cust_industry;
    	}
    	public void setCust_industry(String cust_industry) { 
    		this.cust_industry = cust_industry;
    	}
    	public String getCust_level() { 
    		return cust_level;
    	}
    	public void setCust_level(String cust_level) { 
    		this.cust_level = cust_level;
    	}
    	public String getCust_linkman() { 
    		return cust_linkman;
    	}
    	public void setCust_linkman(String cust_linkman) { 
    		this.cust_linkman = cust_linkman;
    	}
    	public String getCust_phone() { 
    		return cust_phone;
    	}
    	public void setCust_phone(String cust_phone) { 
    		this.cust_phone = cust_phone;
    	}
    	public String getCust_mobile() { 
    		return cust_mobile;
    	}
    	public void setCust_mobile(String cust_mobile) { 
    		this.cust_mobile = cust_mobile;
    	}
    }

**LinkMan类：**

//联系人实体
    public class LinkMan { 
    	//主键
    	private Long lkm_id;
    	
    	private Character lkm_gender;
    	private String lkm_name;
    	private String lkm_phone;
    	private String lkm_email;
    	private String lkm_qq;
    	private String lkm_mobile;
    	private String lkm_memo;
    	private String lkm_position;
    	
    	//表达多对一关系,外键
    	private Customer customer ;
    	
    	public Customer getCustomer() { 
    		return customer;
    	}
    	public void setCustomer(Customer customer) { 
    		this.customer = customer;
    	}
    	public Long getLkm_id() { 
    		return lkm_id;
    	}
    	public void setLkm_id(Long lkm_id) { 
    		this.lkm_id = lkm_id;
    	}
    	public Character getLkm_gender() { 
    		return lkm_gender;
    	}
    	public void setLkm_gender(Character lkm_gender) { 
    		this.lkm_gender = lkm_gender;
    	}
    	public String getLkm_name() { 
    		return lkm_name;
    	}
    	public void setLkm_name(String lkm_name) { 
    		this.lkm_name = lkm_name;
    	}
    	public String getLkm_phone() { 
    		return lkm_phone;
    	}
    	public void setLkm_phone(String lkm_phone) { 
    		this.lkm_phone = lkm_phone;
    	}
    	public String getLkm_email() { 
    		return lkm_email;
    	}
    	public void setLkm_email(String lkm_email) { 
    		this.lkm_email = lkm_email;
    	}
    	public String getLkm_qq() { 
    		return lkm_qq;
    	}
    	public void setLkm_qq(String lkm_qq) { 
    		this.lkm_qq = lkm_qq;
    	}
    	public String getLkm_mobile() { 
    		return lkm_mobile;
    	}
    	public void setLkm_mobile(String lkm_mobile) { 
    		this.lkm_mobile = lkm_mobile;
    	}
    	public String getLkm_memo() { 
    		return lkm_memo;
    	}
    	public void setLkm_memo(String lkm_memo) { 
    		this.lkm_memo = lkm_memo;
    	}
    	public String getLkm_position() { 
    		return lkm_position;
    	}
    	public void setLkm_position(String lkm_position) { 
    		this.lkm_position = lkm_position;
    	}
    }

#### 配置ORM元数据： ####

**Customer.hbm.xml：**

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <hibernate-mapping package="pers.zhang.domain" >
    	<class name="Customer" table="cst_customer" >
    		<id name="cust_id" >
    			<generator class="native"></generator>
    		</id>
    		<property name="cust_name" column="cust_name" ></property>
    		<property name="cust_source" column="cust_source" ></property>
    		<property name="cust_industry" column="cust_industry" ></property>
    		<property name="cust_level" column="cust_level" ></property>
    		<property name="cust_linkman" column="cust_linkman" ></property>
    		<property name="cust_phone" column="cust_phone" ></property>
    		<property name="cust_mobile" column="cust_mobile" ></property>
    	
    		<set name="linkMens" inverse="true" cascade="all" >
    			<key column="lkm_cust_id" ></key>
    			<one-to-many class="LinkMan" />
    		</set>
    		
    	
    	</class>
    </hibernate-mapping>

**LinkMan.hbm.xml：**

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <hibernate-mapping package="pers.zhang.domain" >
    	<class name="LinkMan" table="cst_linkman" >
    		<id name="lkm_id" >
    			<generator class="native"></generator>
    		</id>
    		<property name="lkm_gender" ></property>
    		<property name="lkm_name" ></property>
    		<property name="lkm_phone" ></property>
    		<property name="lkm_email" ></property>
    		<property name="lkm_qq" ></property>
    		<property name="lkm_mobile" ></property>
    		<property name="lkm_memo" ></property>
    		<property name="lkm_position" ></property>
    		
    		<many-to-one name="customer" column="lkm_cust_id" class="Customer" ></many-to-one>
    		
    	</class>
    </hibernate-mapping>

#### 准备数据： ####

![在这里插入图片描述][20191007145617302.png]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70 2]

#### 测试默认情况： ####

@Test
    	public void fun1(){ 
    		Session session = HibernateUtils.openSession();
    		Transaction tx = session.beginTransaction();
    		//----------------------------------------------------
    		
    		String hql = "from Customer ";
    		Query query = session.createQuery(hql);
    		List<Customer> list = query.list();
    		
    		for(Customer c:list){ 
    			System.out.println(c.getLinkMens());
    		}
    		
    		//----------------------------------------------------
    		tx.commit();
    		session.close();
    		
    	}

Hibernate打印：

Hibernate: 
        select
            customer0_.cust_id as cust_id1_0_,
            customer0_.cust_name as cust_nam2_0_,
            customer0_.cust_source as cust_sou3_0_,
            customer0_.cust_industry as cust_ind4_0_,
            customer0_.cust_level as cust_lev5_0_,
            customer0_.cust_linkman as cust_lin6_0_,
            customer0_.cust_phone as cust_pho7_0_,
            customer0_.cust_mobile as cust_mob8_0_ 
        from
            cst_customer customer0_
    Hibernate: 
        select
            linkmens0_.lkm_cust_id as lkm_cus10_1_0_,
            linkmens0_.lkm_id as lkm_id1_1_0_,
            linkmens0_.lkm_id as lkm_id1_1_1_,
            linkmens0_.lkm_gender as lkm_gend2_1_1_,
            linkmens0_.lkm_name as lkm_name3_1_1_,
            linkmens0_.lkm_phone as lkm_phon4_1_1_,
            linkmens0_.lkm_email as lkm_emai5_1_1_,
            linkmens0_.lkm_qq as lkm_qq6_1_1_,
            linkmens0_.lkm_mobile as lkm_mobi7_1_1_,
            linkmens0_.lkm_memo as lkm_memo8_1_1_,
            linkmens0_.lkm_position as lkm_posi9_1_1_,
            linkmens0_.lkm_cust_id as lkm_cus10_1_1_ 
        from
            cst_linkman linkmens0_ 
        where
            linkmens0_.lkm_cust_id=?
    Hibernate: 
        select
            linkmens0_.lkm_cust_id as lkm_cus10_1_0_,
            linkmens0_.lkm_id as lkm_id1_1_0_,
            linkmens0_.lkm_id as lkm_id1_1_1_,
            linkmens0_.lkm_gender as lkm_gend2_1_1_,
            linkmens0_.lkm_name as lkm_name3_1_1_,
            linkmens0_.lkm_phone as lkm_phon4_1_1_,
            linkmens0_.lkm_email as lkm_emai5_1_1_,
            linkmens0_.lkm_qq as lkm_qq6_1_1_,
            linkmens0_.lkm_mobile as lkm_mobi7_1_1_,
            linkmens0_.lkm_memo as lkm_memo8_1_1_,
            linkmens0_.lkm_position as lkm_posi9_1_1_,
            linkmens0_.lkm_cust_id as lkm_cus10_1_1_ 
        from
            cst_linkman linkmens0_ 
        where
            linkmens0_.lkm_cust_id=?

可以看出，在for循环中，每一次使用linkMan，Hibernate都需要查询一次，数据库中共有2个Customer，所以对应查询了两次Customer关联的所有LinkMan。

**修改映射文件：**

<set name="linkMens" batch-size="3">
    	<key column="lkm_cust_id" ></key>
    	<one-to-many class="LinkMan" />
    </set>

再次执行JUnit测试，Hibernate打印：

可以看出，Hibernate一次就将2个Customer对应的所有LinkMan全部查询加载。

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[20191007145617302.png]: https://img-blog.csdnimg.cn/20191007145617302.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NvbGRfX19wbGF5_size_16_color_FFFFFF_t_70 2]: /images/20210813/cbe72aa78f6d4719874f7e0d353d7ca6.png