Lazy loading and Fetch in Hibernate

Lazy Loading in Hibernate

1. Class-level query policy:

Lazy:true (default value)

False (Load Now)

2. Many-to-one associated query strategy:

Lazy:proxy (default value)

No-proxy

False

3. One-to-many or many-to-many

Lazy:true (default value)

False

Extra

Fetch: Affects hibernate generation for the underlying SQL

First, the class level of the EMP mapping file is set to non-lazy loading

The second one will report a null pointer exception

Second, the EMP mapping file class level set non-lazy loading, its many-to-one property is also set to non-lazy loading

Test code

Third, the EMP mapping file class level set non-lazy load, many to one node set delay loading and fetch= "join"

conclusion 1: When fetch and lazy are in the same time, set fetch= "join", the lazy properties will lose its function, that is no longer guaranteed non-lazy loading, but immediately loaded

Iv. when using the list () method of the query interface, the fetch= "join" lazy property is re-enforced

Conclusion: Using the list () method of the query interface, fetch= "join", the Lazy property is re-effective, which is determined by the mechanism of the list itself, list can only put data into memory, cannot fetch data from memory, must force access to the database

Lazy loading and Fetch in Hibernate