ssh lazy机制（懒惰的机制SSH）.docVIP

ssh lazy机制（懒惰的机制SSH） Dont use lazy queries 1: multiple table queries for single data When using the super.getHibernateTemplate ().Get () query, you can get the data of the tables associated with him Such as: petInfo and petDiary tables ApplicationContext CTX = new ClassPathXmlApplicationContext (applicationContext.xml); PetBiz biz = (PetBiz) ctx.getBean (petBiz); PetInfo p= biz.get (9); Iterator, t=, p.getPetDiaries (),.Iterator (); While (t.hasNext ()) { PetDiary o= (PetDiary) t.next (); System.out.println (o.getDiaryAuthor ()); data obtained from petDiary based on PetInfo Two: multi table query of multiple data You cannot use hql= from petInfo to obtain multiple table data. Use connection queries Such as: Hql= from, PetDiary, D, inner, join, fetch, d.petInfo ---------------------------------------------------------------------------------------------------------------- Use the lazy query ------------------------- delayed retrieval strategy The lazy attribute of the class element of the petInfo.Hbm.xml file is set to true, indicating the use of a deferred retrieval strategy This way, using the above get () to get a single data will be wrong: Error message for: A delayed search policy is configured for a class or collection, You must then initialize the proxy class instance or the collection of agents in a persisted state, that is, within the Session range. If it is initialized in a free state, a delay initialization error is generated. When the load () method of the Session is executed, Hibernate does not immediately execute the select statement of the query CUSTOMERS table, Returns only the instance of the proxy class of the Customer class, which has the following characteristics: (1) dynamically generated by Hibernate at run time It extends the Customer class Therefore, it inherits all the attributes and methods of the Customer class, However, its implementation is transparent to the application. (2) when Hibernate creates an instance of the Customer proxy class,