用編程方式證明Hibernate中一級緩存的存在

寫一個查詢小例子

// 測試一級緩存的存在
    @Test
    public void demo8(){
        Session session = HibernateUtils.openSession();
        Transaction transaction = session.beginTransaction();
                                                                                    
        Book book = (Book) session.get(Book.class, "2c2882bc42f1e93b0142f1e93d2c0000");
        System.out.println(book);
        System.out.println("========================================================");
        // 再次執行同樣的查詢 -- 直接使用一級緩存中的數據
        Book book1 = (Book) session.get(Book.class, "2c2882bc42f1e93b0142f1e93d2c0000");
        System.out.println(book1);
                                                                                    
        transaction.commit();
        session.close();
    }

看log

14:43:04,171  INFO TableMetadata:66 - columns: [first_name, last_name]
14:43:04,171  INFO TableMetadata:68 - foreign keys: []
14:43:04,181  INFO TableMetadata:69 - indexes: [primary]
14:43:04,181  INFO SchemaUpdate:217 - schema update complete
Hibernate:
    select
        book0_.id as id1_0_,
        book0_.name as name1_0_,
        book0_.price as price1_0_
    from
        hbm3.tbl_book book0_
    where
        book0_.id=?
Book [id=2c2882bc42f1e93b0142f1e93d2c0000, name=Hibernate入門經典, price=23.0]
========================================================
Book [id=2c2882bc42f1e93b0142f1e93d2c0000, name=Hibernate入門經典, price=23.0]

第一次查詢的時候打印出了sql語句，第二次沒有sql語句。

說明：第二次沒有從DB中去讀取數據，從哪兒拿的數據呢？ 就是一級緩存，第一次查詢的時候把查詢結果放進了一級緩存第二次直接取出來用。