第六章.MyBatis缓存结构

一级缓存

测试案例：

MyBatisTest.java

        //缓存
        @Test
        public void testFindCustomerCache1() throws Exception{  

            SqlSession sqlSession=dataConn.getSqlSession();    

            //调用userMapper的方法
            Customer customer1=sqlSession.selectOne("test.findCustomerById",);
            System.out.println("用户姓名："+customer1.getUsername());

            Customer customer2=sqlSession.selectOne("test.findCustomerById",);
            System.out.println("用户姓名："+customer2.getUsername());
            sqlSession.close();
        }
        

测试结果：

只查询了一次

DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr
用户姓名：Mr
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@42d8062c]

两次查询之间出现增删该查等情况时，即执行commit（）方法。

在UserMapper.xml最后面加上

   <update id="updateCustomerAcNo" parameterType="cn.com.mybatis.po.Customer" >
        UPDATE CUSTOMER SET acno = #{acno} WHERE cus_id=#{cus_id}
    </update>

在MyBatisTest.java中测试

        @Test
        public void testFindCustomerCache2() throws Exception{  

            SqlSession sqlSession=dataConn.getSqlSession();    

            //调用userMapper的方法
            Customer customer1=sqlSession.selectOne("test.findCustomerById",);
            System.out.println("用户姓名："+customer1.getUsername()+"|"
                    +"卡号："+customer1.getAcno());

            String AcNo = "";
            customer1.setAcno(AcNo);
            System.out.println("修改用户卡号为："+AcNo);
            sqlSession.update("test.updateCustomerAcNo",customer1);
            sqlSession.commit();

            Customer customer2=sqlSession.selectOne("test.findCustomerById",);
            System.out.println("用户姓名："+customer2.getUsername()+"|"
                    +"卡号："+customer2.getAcno());

            sqlSession.close();
        }

观察结果：

com.mysql.jdbc.JDBC4Connection@42d8062c]
DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr|卡号：
修改用户卡号为：
DEBUG [main] - ==>  Preparing: UPDATE CUSTOMER SET acno = ? WHERE cus_id=?
DEBUG [main] - ==> Parameters: (String), (Integer)
DEBUG [main] - <==    Updates:
DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@42d8062c]
DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr|卡号：
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@42d8062c]
DEBUG [main] - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@42d8062c]
DEBUG [main] - Returned connection  to pool.

二级缓存

检查Customer.java文件

属性以及是否实现序列化接口

public class Customer implements Serializable{
    private int cus_id;
    private String username;
    private String acno;
    private String gender;
    private String phone;
    private List<Batch> batchList;
....
}

在MyBatisTest.java中测试

    @Test
        public void testFindCustomerOnMapper1() throws Exception{
            SqlSession sqlSession=dataConn.getSqlSession();    

            //获取Mapper代理
            CustomerMapper customerMapper1=sqlSession.getMapper(CustomerMapper.class);
            //执行Mapper代理对象的查询方法
            Customer customer1=customerMapper1.findCustomerById();
            System.out.println("用户姓名："+customer1.getUsername()+"|"
                    +"卡号："+customer1.getAcno());

            //获取Mapper代理
            CustomerMapper customerMapper2=sqlSession.getMapper(CustomerMapper.class);
            //执行Mapper代理对象的查询方法
            Customer customer2=customerMapper2.findCustomerById();
            System.out.println("用户姓名："+customer2.getUsername()+"|"
                    +"卡号："+customer2.getAcno());

            sqlSession.close();
        }
        

得到结果：

DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr|卡号：
用户姓名：Mr|卡号：

若二级缓存中两个查询之间多出了commit()方法的执行？

MyBatisTest.java继续测试

        @Test
        public void testFindCustomerOnMapper2() throws Exception{
            SqlSession sqlSession=dataConn.getSqlSession();    

            //获取Mapper代理
            CustomerMapper customerMapper1=sqlSession.getMapper(CustomerMapper.class);
            //执行Mapper代理对象的查询方法
            Customer customer1=customerMapper1.findCustomerById();
            System.out.println("用户姓名："+customer1.getUsername()+"|"
                    +"卡号："+customer1.getAcno());

            //获取Mapper代理
            CustomerMapper customerMapper2=sqlSession.getMapper(CustomerMapper.class);
            String AcNo = "";
            customer1.setAcno(AcNo);
            //执行Mapper代理对象的修改方法
            customerMapper2.updateCustomerAcNo(customer1);
            System.out.println("修改用户姓名："+customer1.getUsername()+"|"
                    +"的卡号为："+customer1.getAcno());
            sqlSession.commit();

            //获取Mapper代理
            CustomerMapper customerMapper3=sqlSession.getMapper(CustomerMapper.class);
            //执行Mapper代理对象的查询方法
            Customer customer3=customerMapper3.findCustomerById();
            System.out.println("用户姓名："+customer3.getUsername()+"|"
                    +"卡号："+customer3.getAcno());

            sqlSession.close();
        }

测试结果：

DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr|卡号：
DEBUG [main] - ==>  Preparing: UPDATE CUSTOMER SET acno = ? WHERE cus_id=?
DEBUG [main] - ==> Parameters: (String), (Integer)
DEBUG [main] - <==    Updates:
修改用户姓名：Mr|的卡号为：
DEBUG [main] - Committing JDBC Connection [com.mysql.jdbc.JDBC4Connection@13c27452]
DEBUG [main] - ==>  Preparing: SELECT * FROM CUSTOMER WHERE cus_id=?
DEBUG [main] - ==> Parameters: (Integer)
DEBUG [main] - <==      Total:
用户姓名：Mr|卡号：
DEBUG [main] - Resetting autocommit to true on JDBC Connection