MyBatis Fundamentals

1. Database and Dependency Setup

Create a database table:

CREATE TABLE tb_user ( id INT PRIMARY KEY AUTO_INCREMENT, username VARCHAR(20), password VARCHAR(20), gender CHAR(1), addr VARCHAR(30) );

INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京'); INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津'); INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');

Maven dependencies:

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.11</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.46</version>
</dependency>

2. MyBatis Core Configuration

User POJO:

public class User {
    private Integer id;
    private String username;
    private String password;
    private String gender;
    private String addr;
    // Getters and setters
}

Mapper XML:

<?xml version="1.0" encoding="UTF-8" ?>
<mapper namespace="userMapper">
    <select id="selectAll" resultType="com.example.pojo.User">
        SELECT * FROM tb_user
    </select>
</mapper>

MyBatis configuration:

<?xml version="1.0" encoding="UTF-8" ?>
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///pikachu?useSSL=false"/>
                <property name="username" value="kudo"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

3. Testing MyBatis

public class MyBatisTest {
    public static void main(String[] args) throws Exception {
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        
        List<User> users = sqlSession.selectList("userMapper.selectAll");
        System.out.println(users);
        sqlSession.close();
    }
}

Mapper Proxy Development

Enterface definition:

public interface UserMapper {
    List<User> selectAll();
}

Using mapper proxy:

public class MyBatisTest {
    public static void main(String[] args) throws Exception {
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = userMapper.selectAll();
        System.out.println(users);
        sqlSession.close();
    }
}

Advanced Mappper Configuration

Package scanning in MyBatis config:

<mappers>
    <package name="com.example.mapper"/>
</mappers>

Properties loading:

<properties resource="jdbc.properties"/>

Type aliases:

<typeAliases>
    <package name="com.example.pojo"/>
</typeAliases>

Multiple environments configuration:

<environments default="development">
    <environment id="development">
        <!-- Development config -->
    </environment>
    <environment id="test">
        <!-- Test config -->
    </environment>
</environments>

Spring Integration with MyBatis

Annotated DAO interface:

package com.example.dao;

import com.example.pojo.User;
import org.apache.ibatis.annotations.Select;
import java.util.List;

public interface UserDao {
    @Select("SELECT * FROM tb_user")
    List<User> selectAll();
}

Spring configuration for MyBatis:

@Configuration
public class MyBatisConfig {
    
    @Bean
    public SqlSessionFactoryBean sqlSessionFactory(DataSource dataSource) {
        SqlSessionFactoryBean ssfb = new SqlSessionFactoryBean();
        ssfb.setTypeAliasesPackage("com.example.dao");
        ssfb.setDataSource(dataSource);
        return ssfb;
    }
    
    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer() {
        MapperScannerConfigurer msc = new MapperScannerConfigurer();
        msc.setBasePackage("com.example.dao");
        return msc;
    }
}

Service implementation:

@Service("userService")
public class UserServiceImpl implements UserService {
    
    @Autowired
    private UserDao userDao;

    public List<User> selectAll(){
        return userDao.selectAll();
    }
}

JUnit Integration with Spring

Dependencies:

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13.1</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>5.2.10.RELEASE</version>
</dependency>

Test class:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = SpringConfig.class)
public class UserServiceTest {
    
    @Autowired
    private UserService userService;

    @Test
    public void testSelectAll(){
        System.out.println(userService.selectAll());
    }
}

Aspect-Oriented Programming (AOP)

Basic aspect definition:

@Component
@Aspect
public class MyAspect {
    
    @Pointcut("execution(void com.example.service.UserService.update())")
    private void pc(){}

    @Before("pc()")
    public void logTimestamp() {
        System.out.println(System.currentTimeMillis());
    }
}

AOP configuration:

@Configuration
@ComponentScan("com.example")
@EnableAspectJAutoProxy
public class SpringConfig {
}

Password trimmnig aspect:

@Component
@Aspect
public class PasswordTrimmer {
    
    @Pointcut("execution(boolean com.example.service.ResourcesService.yesorno(*,*))")
    public void pt(){}

    @Around("pt()")
    public Object trimStrings(ProceedingJoinPoint pjp) throws Throwable {
        Object[] args = pjp.getArgs();
        for (int i = 0; i < args.length; i++) {
            if (args[i] instanceof String) {
                args[i] = ((String) args[i]).trim();
            }
        }
        return pjp.proceed(args);
    }
}