SpringData-Object Navigation Query

Object navigation query: When querying an object, query all related objects through this object.

Based on many operating table article, create a test class:

One check and many (check all contacts associated with the customer according to the customer)

1. getOne(Long id) defaults to lazy loading

@Test
@Transactional   //解决在java代码中的no session问题
public void testQuery1() {
    //查询id为 1 的客户
    Customer customer = customerDao.getOne(1L);
    //对象导航查询，此客户下的所有联系人
    Set<LinkMan> linkMans = customer.getLinkMans();
    for (LinkMan linkMan : linkMans) {
        System.out.println(linkMan);
    }
}

2. findOne(Long id) is loaded immediately by default

Configure one-to-many table relationship mapping in one class to load immediately (fetch = FetchType.EAGER)

/**
  * fetch : 配置关联对象的加载方式
  *          EAGER   ：立即加载
  *          LAZY    ：延迟加载
  */
@OneToMany(mappedBy = "customer", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private Set<LinkMan> linkMans = new HashSet<>();

@Test
@Transactional   //解决在java代码中的no session问题
public void testQuery2() {
    //查询id为 1 的客户
    Customer customer = customerDao.findOne(1L);
    //对象导航查询，此客户下的所有联系人
    Set<LinkMan> linkMans = customer.getLinkMans();
    System.out.println(linkMans.size());
}

Check one more (check the customer associated with the contact according to the contact) The default is to load immediately

Lazy loading of many-to-one table relationship mapping can be configured in the multi-party class (fetch = FetchType.LAZY):

@ManyToOne(targetEntity = Customer.class, fetch = FetchType.LAZY)
@JoinColumn(name = "lkm_cust_id", referencedColumnName = "cust_id")
private Customer customer;

@Test
@Transactional // 解决在java代码中的no session问题
public void testQuery3() {
    //查询id为 1 的联系人
    LinkMan linkMan = linkManDao.findOne(1L);
    //对象导航查询所属的客户
    Customer customer = linkMan.getCustomer();
    System.out.println(customer);
}

*** recommended many queries

SpringData-Object Navigation Query

Guess you like