mybatis源码-执行器

执行查询：

1、简单执行器SimpleExecutor：

private static void simpleExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://ip:3306/mybatis?serverTimezone=UTC","user","pwd"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    SimpleExecutor executor = new SimpleExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.getPersonById");
    List<Object> objects = executor.doQuery(
            ms,
            "20210420172645864088a2a1ba11eb886d525400146075",
            RowBounds.DEFAULT,
            SimpleExecutor.NO_RESULT_HANDLER,
            ms.getBoundSql("20210420172645864088a2a1ba11eb886d525400146075")
    );
    System.out.println(objects);

}

再一模一样的查询一次

private static void simpleExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://ip:3306/mybatis?serverTimezone=UTC","user","pwd"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    SimpleExecutor executor = new SimpleExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.getPersonById");
    List<Object> objects = executor.doQuery(
            ms,
            "20210420172645864088a2a1ba11eb886d525400146075",
            RowBounds.DEFAULT,
            SimpleExecutor.NO_RESULT_HANDLER,
            ms.getBoundSql("20210420172645864088a2a1ba11eb886d525400146075")
    );
    executor.doQuery(
            ms,
            "20210420172645864088a2a1ba11eb886d525400146075",
            RowBounds.DEFAULT,
            SimpleExecutor.NO_RESULT_HANDLER,
            ms.getBoundSql("20210420172645864088a2a1ba11eb886d525400146075")
    );
    System.out.println(objects);

}

==>  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
[Person{id='20210420172645864088a2a1ba11eb886d525400146075', name='李四', sex='1', age='20', createTime='2021-04-20 17:26:45'}]

2、可重用执行器ReuseExecutor

private static void reuseExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://www.aimaboge.com:3306/mybatis?serverTimezone=UTC","root","password"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    ReuseExecutor executor = new ReuseExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.getPersonById");
    List<Object> objects = executor.doQuery(
            ms,
            "20210420172645864088a2a1ba11eb886d525400146075",
            RowBounds.DEFAULT,
            SimpleExecutor.NO_RESULT_HANDLER,
            ms.getBoundSql("20210420172645864088a2a1ba11eb886d525400146075")
    );
    executor.doQuery(
            ms,
            "20210420172645864088a2a1ba11eb886d525400146075",
            RowBounds.DEFAULT,
            SimpleExecutor.NO_RESULT_HANDLER,
            ms.getBoundSql("20210420172645864088a2a1ba11eb886d525400146075")
    );
    System.out.println(objects);

}

==>  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
==> Parameters: 20210420172645864088a2a1ba11eb886d525400146075(String)
<==    Columns: id, name, sex, age, create_time
<==        Row: 20210420172645864088a2a1ba11eb886d525400146075, 李四, 1, 20, 2021-04-20 17:26:45
<==      Total: 1
[Person{id='20210420172645864088a2a1ba11eb886d525400146075', name='李四', sex='1', age='20', createTime='2021-04-20 17:26:45'}]

重用执行器如果sql一样，那么只预编译一次

3、批处理执行器BatchExecutor

只针对修改操作，对于查询操作与简单执行器SimpleExecutor无异

private static void batchExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://ip:3306/mybatis?serverTimezone=UTC","user","pwd"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    BatchExecutor executor = new BatchExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.updatePersonNameById");
    Map<String, String> param = new HashMap<>();
    param.put("name", "王五");
    param.put("id", "20210420172645864088a2a1ba11eb886d525400146075");
    executor.doUpdate(ms, param);
    executor.doUpdate(ms, param);

}

==>  Preparing: update set name = ? from person where id = ?
==> Parameters: 王五(String), 20210420172645864088a2a1ba11eb886d525400146075(String)
==> Parameters: 王五(String), 20210420172645864088a2a1ba11eb886d525400146075(String)

对于修改操作只预编译了一次

执行后，查看数据库未发生更新，是因为没有批处理刷新，需执行executor.doFlushStatements(false);进行刷新

private static void batchExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://ip:3306/mybatis?serverTimezone=UTC","user","pwd"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    BatchExecutor executor = new BatchExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.updatePersonNameById");
    Map<String, String> param = new HashMap<>();
    param.put("name", "王五");
    param.put("id", "20210420172645864088a2a1ba11eb886d525400146075");
    executor.doUpdate(ms, param);
    executor.doUpdate(ms, param);
    executor.doFlushStatements(false);
}

再次查看数据库，可以看到已经更新

4、基础执行器BaseExecutor

private static void baseExecutorTest() throws SQLException, IOException {

    String resource = "mapper/mybatis-config.xml";
    InputStream inputStream = Resources.getResourceAsStream(resource);
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    Configuration configuration = sqlSessionFactory.getConfiguration();
    Connection connection = DriverManager.getConnection(
            "jdbc:mysql://ip:3306/mybatis?serverTimezone=UTC","user","pwd"
    );
    JdbcTransaction jdbcTransaction = new JdbcTransaction(connection);
    BaseExecutor executor = new SimpleExecutor(configuration, jdbcTransaction);
    MappedStatement ms = configuration.getMappedStatement("com.laoxu.mybatis.mapper.PersonMapper.getPersonById");
    executor.query(ms, "20210420172645864088a2a1ba11eb886d525400146075", RowBounds.DEFAULT, Executor.NO_RESULT_HANDLER);
    executor.query(ms, "20210420172645864088a2a1ba11eb886d525400146075", RowBounds.DEFAULT, Executor.NO_RESULT_HANDLER);

}

只预编译了一次，只查询了一次，这就是走了一级缓存

==>  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

第一次查询进行创建缓存的key：

执行query查询方法：

尝试获取缓存，如果没有获取到就置null

list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;

如果为null那么直接查询数据库：

可以看到查询数据库方法中进行了缓存：

localCache.putObject(key, EXECUTION_PLACEHOLDER);

当下次查询的时候，直接查询缓存返回

总结：

涉及到的模式：