1 hibernate 一级缓存
Session
evict(Object o) 从缓存中清除指定的持久化对象
clear() 清除缓存中所有对象
2 批量更新于批量删除
1) 批量更新
Iterator customers=session.find("from Customer c where c.age>0");
while(customers.hasNext()){
Customer customer=(Customer)customers.next();
customer.setAge(customer.getAge()+1);
}
tx.commit();
session.close();
缺点：内存中加载了大量数据
执行了多次update 语句
改进
Iterator customers=session.find("from Customer c where c.age>0");
while(customers.hasNext()){
Customer customer=(Customer)customers.next();
customer.setAge(customer.getAge()+1);
session.flush();
session.evict(customer);
}
tx.commit();
session.close();
遗留问题
执行了多次update 语句
采用jdbc api 进行调用
Connection con=session.connection();
PrepareStatement stmt=con.prepareStatement("update customers set age=age+1 where age>0");
stmt.executeUpdate();
tx.commit();
另外，也可以调用底层的存储过程进行批量更新
create or replace procedure batchUpdateCustomer(p_age,in number) as
begin
update customer set age=age+1 where age>p_age;
end;
tx=session.beginTransaction();
Connection con=session.connection();
CallableStatement cstmt=con.prepareCall(batchUpdateCustomer);
cstmt.setInt(1,0);
cstmt.eqecuteUpdate();
tx.commit();
2) 批量数据的删除
session.delete("from Customer c where c.age>0");
实际调用的过程
session * from Customer where age>0;
在把所有数据加载到内存之后执行多条delete 语句
delete from customer where id=i;
.......................
改进办法采用jdbc api 进行批量数据的删除
tx=session.beginTransaction();
Connection con=session.connection();
con.execute("delete from customers where age>0");
tx.commit();