mybatis源码-一级缓存命中的场景

命中条件：

1、sql和参数必须一模一样

private static void test1() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        Person person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        Person person2 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }
}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
true

private static void test1() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        Person person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        Person person2 = personMapper.getPersonById("20210420172922e412b7bea1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }
}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172922e412b7bea1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172922e412b7bea1ba11eb886d525400146075, 张三, 1, 20, 2021-04-20 17:29:22
<==      Total: 1
false

2、statementId必须一样

private static void test1() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        Person person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        Person person2 = personMapper.getPersonById2("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }
}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

3、必须是同一次会话

private static void test2() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
    }
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person2 = personMapper.getPersonById2("20210420172645864088a2a1ba11eb886d525400146075");
    }
    System.out.println(person1==person2);
}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@55493582]
Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@55493582]
Returned connection 1430861186 to pool.
false

4、RowBounds返回行范围必须相同

RowBounds对结果集进行分页

private static void test3() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        RowBounds rowBounds = new RowBounds(0, 10);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        List<Person> people = session.selectList(
                "com.laoxu.mybatis.mapper.PersonMapper.getPersonById",
                "20210420172645864088a2a1ba11eb886d525400146075", rowBounds);
        person2 = people.get(0);
        System.out.println(person1==person2);

    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

private static void test3() throws IOException {

        String resource = "mapper/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        Person person1;
        Person person2;
        try (SqlSession session = sqlSessionFactory.openSession()) {
            PersonMapper personMapper = session.getMapper(PersonMapper.class);
//            RowBounds rowBounds = new RowBounds(0, 10);
            RowBounds rowBounds = RowBounds.DEFAULT;
            person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
            List<Person> people = session.selectList(
                    "com.laoxu.mybatis.mapper.PersonMapper.getPersonById",
                    "20210420172645864088a2a1ba11eb886d525400146075", rowBounds);
            person2 = people.get(0);
            System.out.println(person1==person2);

        }

    }

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
true

5、没有手动清空缓存

private static void test4() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        session.clearCache();
        person2 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

6、没有配置执行查询后清空缓存

@Select("select * from person where id = #{id}")
@Options(flushCache = Options.FlushCachePolicy.TRUE)
Person getPersonById3(String id);

private static void test5() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById3("20210420172645864088a2a1ba11eb886d525400146075");
        person2 = personMapper.getPersonById3("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

private static void test6() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");

        personMapper.getPersonById3("20210420172645864088a2a1ba11eb886d525400146075");

        person2 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

7、没有执行update

private static void test7() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");

        personMapper.updatePersonNameById("20210420172645864088a2a1ba11eb886d525400146075", "李大爷");
        session.commit();

        person2 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
==>  Preparing: update person set `name` = ? where id = ?
==> Parameters: 李大爷(String), 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Updates: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李大爷, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false

8、缓存的作用域不能是STATEMENT

配置localCacheScope值为STATEMENT

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="config.properties">
        <!--        按需定义全局变量，以供整个配置文件使用-->
        <!--        <property name="globalVariable" value="value"/>-->
    </properties>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING" />
        <setting name="localCacheScope" value="STATEMENT" />
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${mysql.driver}"/>
                <property name="url" value="${mysql.url}"/>
                <property name="username" value="${mysql.username}"/>
                <property name="password" value="${mysql.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/PersonMapper.xml"/>
    </mappers>
</configuration>

private static void test8() throws IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Person person1;
    Person person2;
    try (SqlSession session = sqlSessionFactory.openSession()) {
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        person1 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        person2 = personMapper.getPersonById("20210420172645864088a2a1ba11eb886d525400146075");
        System.out.println(person1==person2);
    }

}

==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
Cache Hit Ratio [com.laoxu.mybatis.mapper.PersonMapper]: 0.0
==>  Preparing: select * from person where id = ?
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
false