Discussion on Hibernate Lazy Loading Issue (Multiple Foreign Key Associations)

The database structure is as follows

The 'strategy' table has foreign keys 'member_id' (associated with the 'member' table) and 'strategy_category' (associated with the 'category' table), while the 'member' table has a foreign key 'position_id' (associated with the 'positions' table)

If the front-end page directly queries the content of the stategy table, our HQL statement would be written like this

Stringhql="FromStrategywhereid=:id";

The console will report a nosession error because hibernate defaults to lazy loading, which will only load associated objects when needed. In our front-end, when we need to take the properties of the associated objects, the session has already been closed, and such an error will be reported.

So how to solve it

It is recommended to use the leftjoinfetch method to load objects instead of changing the lazy loading by default in the annotation, as the efficiency will be very low

The statement is as follows

Strategystrategy=(Strategy)sessionFactoryUtil.getSession()
.createQuery("FromStrategysleftjoinfetchs.strategyCategoryleftjoinfetchs.memberleftjoinfetchs.member.positionswheres.id=:id")
.setInteger("id",id).uniqueResult();

It should be noted here that because the member table associated with the member table also associates with the positions table, it is necessary to load the other table together. Another thing to note is that the s.id must be written like this because the primary key name of each table is id, and if it is not specified, the system cannot identify it.

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